Sugar content in tomatoes.(submitted by C. Jucci)
Bianchi, A., A. Forlani, and C. Manunta
Italian, Canadian, English, Australian varieties give mean values amounting to 3-6%. Higher values are found in "Palla Oro" (rrTT) and in Blood Orange. A tetraploid form shows values of 4.1-4.3%. The L. pimpinellifolium presents a far higher value, 8.84%. Studying Fl and F2 of the crosses of this species with esculentum variety San Marzano, which has a sugar content of 4.6%, we found for F1, 6.55, for F2, 6.62. For each plant we assayed three fruits, small, medium and large-sized; no correlation appears between size and sugar concentration. In the F2 appears a tendency (P=0.05) toward association of a high sugar content and spheroidal form of the fruit (pimpinellifolium type).
A fertile, stamenless males sterile mutant.
Bishop, C. J.
Among a number of male sterile tomatoes discovered in stock growing at the Experimental Station, Kentville, Nova Scotia, one has been propagated which has flowers that in most cases have no stamens. This tomato resembles the mutant pi reported by Rick and Robinson (1951), but unlike that one has proven to be perfectly fertile when used as a female parent.
Other than lacking stamens the flowers appear normal and open fully.
The plant may be propagated by cuttings, but in addition, it has been found under certain conditions to produce abnormal anthers with viable pollen. Seedlings produced from selfing have been entirely of the male sterile type. The exact conditions which favor stamen development are not known, but are being studied with the aim of producing larger male sterile populations by seed.
Crosses made with other varieties indicate that the condition is due to the action of a single recessive gene, and F2 segregation of the P1 male sterile type has been obtained. The symbol sl (stamenless) is assigned to this gene. Limited seed is available for anyone caring to work out its linkage relationships.
The effect of thermal neutrons on tomato seed.
Burdick, A. B.
Different lots of four different genetic types were treated to two, four, and eight hours of thermal neutron irradiation. The treated seed was grown along with a control in two replications in the greenhouse. The following table summarizes the principle results.
Genetic Types: 1 - 4n Ex-Haploid pimpinellifolium 2 - 2n Ex-Haploid "D" 3 - 2n Ex-Haploid "d" 4 - 2n Ex-Haploid pimpinellifolium Mean Mean Genetic Types Per cent Days to Disregarding Germination Germination Treatment _______________________________________ 1 76 9.6 2 13 10.6 3 57 14.5 4 61 9.2 Mean Mean Thermal Neutron Percent Days to Treatments Disregarding Germination Germination Genetic Types __________________________________________________ Control 53 10.6 2 Hours 55 11.9 4 Hours 54 10.6 8 Hours 46 10.3There was no apparent decrease in germination percentage nor were there any detectable differences of days to germination among the various treatments. Shortly after germination, the plants resulting from thermal neutron radiation showed a considerable amount of leaf sectoring. In no instance did the mutant sector include the growing point. Cytological examination of the treated material has not been completed.
The mutation rate in the tomato.
In checking tomato stocks or segregating generations, one often comes upon an aberrant individual. If this individual resembles a known gene that has been grown previously, or is carried in the seed stocks, then the aberrant plant is usually regarded as a contaminant. For this reason we have few records of the mutation rate at known loci. In 1950 two cases occurred which were undoubtedly new mutations. The first was in 3213 sel. d dm br wt al lf j f H where the wt mutated to Wt. There were ten plants of this parent stock set out and 6 were Wt and 4 wt. On testing the stock from which this seed came, we found that a plant of wt phenotype gave a segregation of 98 normal to 30 wilty. All other marker genes were unchanged. The second case was in 706 sel. d p o s r y where the ten plants gave 7 S: 3 s. The seed came from a 706 plant grown years previously which had been classified as compound infloresence. Further plants of seed from this source gave 125 S: 47 s. In both cases these selections had previously bred true for almost twenty years and during that time some 400 plants of each was grown by us.
The number of plants concerned in the previous example was too small to make any estimate of the mutation rate, but a rough estimate can be made from the following data: In the past twenty years I have checked a little over 140,000 plants and have observed five dominant mutations. Four of these were yellcw foliage types, and one was similar to smooth H but not identical with it. Since it would have been a prodigious task to test all these plants for recessive mutants no check was made, but if we assume a ratio of 1 dominant to ten recessive (as shown by the known genes) then we should expect a mutation in every 3,000 plants.
Recent observations indicate that we should watch a little more closely for mutations and not discard aberrant plants without a test. It appears that all green stem plants are not a, all wilty plants are not wt, and all determinate are not sp.
Changes in gene symbols.
In order to serve as an effective means of communication between tomato workers, gene symbols should be standardized and free from synonyms. For instance, in correspondence with Dr. Rick it has been necessary for me to write broad leaf as b (e), or simply refer to it as broad leaf without a symbol. In writing to me, he has used opposite notation, the at present this is a minor point, with the discovery of other broad leafs and the active use of b for the beta-carotene gene, this could become complicated or lead to misunderstandings. The adoptions of the proposed rules of nomenclature enclosed in this report,should help to keep us all speaking the same language as far as new genes are concearned, but some revision of present symbols is necessary. It is expected that genes which do not fit the proposed rules but which are clearly established, will not be changed. The major changes will be made in gene symbols which have synonyms. Since I am largely responsible for some of the present confusion in symbols, I propose the following be adopted as the standard symbol for the loci named:
e for entire leaf instead of b for broad leaf for the linkage group XI gene.
a for anthocyaninless, or the green stem of group V.
a\1\ for anthocyanin-loser instead of a\2\ in group VIII.
dm for dwarf modifier instead of d\2\ in group IX.
ps for position sterile instead of va. The symbol va was used by me for the John Baer functional male sterile. Our linkage tests indicate that this gene is in group I.
el for the fruit-elongation gene from Oxheart; the symbol a previously proposed is now rejected because the e for entire leaf has priority. The genes for Cladosporium resistance will be added to shortly, so I propose the present unwieldy symbols be discarded in favor of a numerical system. The new genes to be numbered in order of discovery and the old ones to be renamed as
Cf\1\ for Cladosporium fulvum resistance instead of Cf\sc\ of group III.
Cf\2\ for Cladosporium fulvum resistance instead of Cf\p1\ of group IV.
Cf\3\ for Cladosporium fulvum resistance instead of Cf\p2\ of group V.
A new member of the first linkage group.
In the past summer the gene ps for functional male sterile, was tested against markers for all twelve linkage groups. The cross-over values were close to 50% in all cases except with the gene d of linkage group I. The F2 segregation for this was D Ps 21l: D ps 107: d Ps 91: d ps 2. This gives a crossover of 14.3% with an error of 5%. The tester stock cotained no other linkage group I genes so it is impossible to say from these data on which side of dwarf the ps gene is located. Crosses have now been made which will determine this. It is expected that the application of some of the newer techniques will enable a better map to be made of linkage group I which is on chromosome 2. It should be possible now that this group consists of ten genes, to locate the spindle fibre attachment, thus giving a point of reference to chromosom 2.
Additional data on the linkage relations of ms\10\
Butler, L., and C. M. Rick
The linkage of ms with d in group I as ascertained from F2 segegregations was reported in TGC No. 2. During the past season more critical information based on a backcross involving ms\10\, Wo and d has been obtaned. Part of the population was grown at Davis, California, part at Guelph, Ontario. Since the proportions do not differ appreciably, the frequencies obtained at the two stations were added, giving the following totals.
Cross: ms + d + Wo d ms + d ms + + Progeny: + + + 3 ms + + 131 + + d 3 ms + d 35 +Wo + 184 ms Wo + 0 +Wo d 305 ms Wo d 1Considering gene frequency first, we observe a normal segregation of d(52.0%), but a very significant deficiency of ms(25.5%), and a very significant excess of Wo(74.0%). The excess of Wo so nicely balances the shortage of ms, that it is tempting to suppose the deviations result from inviability of some ms segregates and that, thanks to the tight linkage between Wo and ms\10\, wooly plants appear in excess. It is peculiar that ms should be so deficient in this material, while no significant discrepancy has yet been observed in many F2 and BC families in pure San Marzano background. Possibly the viability of ms\10\ is "balanced" in a uniform SM background, but when injected into the heterozyge of a wide cross, such as this one with Wo-d stock, many combinations with ms are not viable.
In contrast to the position indicated in the previous report (based on much less critical data) these new figures indicate a crossover value of 1.1 between ms\10\ and Wo, and of 33.5 between ms\10\ and d. The crossover value between Wo and d also turns out to be 33.5. Since ms\10\ and Wo are so close it is impossible to state on which side of the latter the male-sterility gene lies. This tight linkage provides a handy method of increasing the proportion of sterile plants by roguing out fertile plants in the seedbed, Thus, if the present material had been rogued to non-wooly plants, the proportion of male-sterile plants in the remainder would have been 96.5%, and if rogued to non-wooly, non-dwarf, the proportion would have been 97.8%.
An interesting development in this material was observed in the cultures grown at Guelph. Early in the season difficulty was experienced in classifying fertile and sterile plants, but in September, when we both inspected the planting, the two phenotypes could be distinguished readily. At that time we noticed that the sterile segregates had set fruit abundantly early in the season, but were decidedly less fruitful than fertile segregates in the late season. Seed was harvested from nine sterile, non-wooly, dwarf (ms + d) segregates and grown for observation of seedling characters. The frequencies and proportions of tall and/or wooly hybrids are as follows:
Hybrids d Wo+ % hybrids Hybrids d Wo+ % hybrids _________________________ __________________________ 19 16 54 24 22 52 38 11 78 9 5 64 19 4 82 7 21 25 19 10 65 8 34 19 8 1 89Since many of the surrounding plants were not homozygous for the dominant alleles, this proportion of hybrids provides a minimum estimate of outcrossing. It therefore appears very likely that all seeds set by these plants resulted from hybridization with surrounding plants and none from selfing. Interpreted in this manner, these data suggest that in the early summer at Guelph tomato pollen vectors might be very active. They might also explain why several investigators in eastern states have had difficulty in finding male-sterile mutants by virtue of their possible unfruitfulness.
Evaluating heterosis in tomato improvement.
Currence, T. M.
With regard to the extent of heterosis shown by tomato crosses, there has recently been some discussion of a figure taken from Larson and Currence quoted by Dr. M. L. Odland during the recent conference of Vegetable Breeders at the Cornell A.I.B.S. meetings. Those attending the evening discussion or familiar with the publication, "The extent of Hybrid Vigor in F1 and F2 Generations of Tomato Crosses." Minn. Tech. Bul. 164, June 1944, will recall that the increase in yield by the F1 of 39 percent over the means of parents was given. There may be some misanderstanding as to what this figure is. Larson and Currence presented it in order to suggest an average degree of dominance or hybrid vigor. In evaluating commercial possibilities of hybrid vigor, the relation of the F1 performarce to that of the parental average has limited value. If one or both parents are low then their average becomes low and the hybrid may be comparatively productive without being at all outstanding compared with better varieties. This comparison should not be confused with another that is sometimes used. The F1 may be compared with the better parent if the worker prefers to evaluate heterosis as the superiority of the hybrid over the better parent. Obviously this comparison will give a lower percentage increase. In the group of crosses studied by Larson and Currence it was 19 percent.
A critical and practical test is the performance of the best F1 against the best variety when several of each are grown in replicated trials. Data on this comparison were given by Larson and Currence on page 26 of the above publication. Earliana was the best yielding of several varieties and gave an annual average of 23.47 tons per acre for three years. A cross,3-38 x Valiant, was the best yielding several F1's grown in the same tests. The average annual yield for this cross was 28.72 tons per acre. The increase of 5.25 is approximately 22 per cent of the Earliana yield. Such increases in favor of F1's appear consistently in Minnesota tests while workers at some other stations are unable to obtain them. Reasons for the divergence of behavior are not known. Prevalence of disease, climatic factors and differences in evaluating yields probably are involved. It would be worthwhile to have further observations on this.
The inheritance of fruit shape, locule number and stem color in derivatives of a hybrid of Lycopersicon esculentum by L. peruvianum.
Dennett., R. K., and R, E. Larson
The material studied was in the BC4 of the cross of L. esculentum. Michigan State Forcing by L. peruvianum (P. I. 128,687) made by P. G. Smith in 1944. V. M. Watts made the first backcross to a San Marzano derivative which had a green stem character. W. A. Frazer made three additional backcrosses to L. esculentum types.
Inheritance was studied in F1, F2, F3, and test cross populations. The green stem character which appeared in this material was identical to the phenotypes of the a allele. The character was conditioned by a single gene with the purple completely dominant to green. The symbol aw is suggested since it was determined that the gene was not an allele of a (a\1\) or al (a\2\). Fruit shape was found be determined by a single major gene. Non-ovate fruit (Shape index 0.99 - l.44) was completely dominant tc ovate fruit (Shape index 0.65 - O.95). There was also a complete association of non-ovate fruit, and many locules (3.5 - 12.0) as well as ovate fruit and few locules (2.0 - 3.5). Since no crossing over between these factors was found a single symbol ol is suggested at the present time for what at may be either two closely linked genes or a single pleitropic gene which affects both fruit shape and locule number. Many locules was found to be partially dominant to few locules with the F1 not being significantly different from the geometric mean of the parents. The o and ol genes are probably alleles. A cross of olol by oo gave all ovate fruit in the F1 and F2. The linkage relation of ol are approximately equal to those reported for o although sufficient linkage data were not available to use them as a basis for determining allelomorphism.
The aw allele was found to be linked with the ol allele with approximately two percent crossing over. This linkage emphasized the monogenic frequency distributions of fruit shape and number. The arrangements of these genes in linkage group I is apparently as follows
aw ol d _______ 2 12(The data from which the above abstract was taken will be published as a technical bulletin of the Pennsylvania Experiment Station in the near future.
Dennett, R. K., B. L. Pollack, and R. E. Larsen
Trifoliate leaf, a new mutant.
In 1950 a planting of the variety Oahu was found to contain strikingly off-type plants at a frequency of about five percent. The seed lot for this planting was obtained by massing the seed from about thirty normal appearing plants. Crosses of the off-type by normal plants produced an F1 which was normal and an F2 segregation of 248 normal to 79 off-type plants. In addition seed taken from the off-type plants produced only off-type plants. Thus it appears that this unusual characteristic is conditioned by a singla recessive gene. This gene has baen designated as tf since trifoliate leaf is one of the most distinctive features of the off-type plants.
These off-type plants are unique in several ways, of which the most prominent is the trifoliate leaf. This characteristic can first be observed in the seedlings when the first true leaves appear. The tf plants also have abnormally long petioles, a tendency to develop fewer stems, and a partial sterility. This sterility is apparently due to reduced production of pollen. Detailed cytological studies of the nature of the sterility have not been made. Limited study of meiosis of the off-type plants has shown no apparent abnormalities. The Fl plants are fully fertile, however.
Typical pollen counts of mature flowers are as follows: tf tf 354 Normal 2035 Aborted 14% Normal Tf tf 2654 2837 48% Tf Tf 315 14 95%Apparently microsporogenesis is normal up to the tetrad stage with a subsequent pollen abortion.
Linkage studies in the F2 have failed to show any association of tf and u, mc s, d, f, or j.
Die Struktur der satelliten-Chromosomen verschiedener Tomatensorten
Wenn man die Pachytan-Chromosomen der Pollenmutterzellen verschisdener Tomatensorten mitainander vergleicht, so lasst sich bei den meisten Chromosomen des Tomaten-Genoms eine weitgehande Ubereinatimmung der Struktur einander entsprechender Chromosomen in den verschiedenen Sorten feststellen. Diese Ubereinstimmung gilt jedoch nicht fur bestimmte Regionen des Satelliten-Chromosoms. Die euchromatischen Enden und das heterochromatische Segment dieses Chromosoms zeigten bei insgesamt 10 verschiedenen Sorten in ihrem strukturellen Aufbau praktisch keine Unterschiede, wahrend in der Gestaltung des Satelliten zum Teil erhebliche Differenzen nachgewiesen werden konnten. Im einfachsten Fallbesitzt der Satellit nur die Grosse eines der Makrochromomeren, der Bausteine des Heterochromatins und tritt nicht als besonderes Strukturelement des Chromosoms in Erscheinung ("Triumph"). Bei anderen Formen ist er kugelformig ausgebildet und hat die Gestalt eines vergrosserten Makrochromomers ("Konig Humbert", "Blondkopfchen"). Bei den restlichen unter suchten Sorten liegt der Satellit in Form eines unterschiedlich langen, tief heterochromatischen Chromosomensegments vor, das sich in seiner Struktur kaum von einer gleichlangen heterochromatischen Partie unterscheiden lasst. Die Lange des Satelliten schwankt bei den untersuchten Sorten zwischen 1,5 und 13,5 (siehe Tabelle).
_________________________________________________________ untersuchte Sorte Lange des Satel- Lange der achromati- liten in u schen Zone in u _________________________________________________________ Triumph -- -- Konig Humbert 1,5 3,0 Blondkopfchen 2,O -- Roter Zwerg 3,0 5,0 Red Pear 7,0 4,0 Yellow Pear 8,0 2,5 Fruhrot 10,5 1,0 Express 10,5 -- Ficarazzi 13,0 3,O Mikado 13,5 -- _________________________________________________________Auch die Lange der nicht farbbaren Region zwischen dem Satelliten und dem heterochromatischen Segment des SAT-Chromosoms, das Bildungszentum fur den Nucleolus also variiert bei den untersuchten Sorten erheblich. Bei einigen Formen tritt diese Region uberhaupt nicht oder nur als ganz kurze Lucke in Erscheinung ("Triumph", "Express", "Blondkopfchen", "Mikado", "Fruhrot"), wahrend sie bei "Red Pear" sine Lange von 4, bei "Roter Zwerg" sogar eine Lange von 5 u erreicht. Aus der Tabelle geht hervor, dass eine Beziehung zwischen der Lange des Satelliten und der Ausdehnang der achromatischen Zone nicht besteht.
(Die Zahlenwert der Tabelle sind Mittelwerte aus jeweils 20 Chromosomenmessungen.)
English summary: The structure of the satellite of chromosome (2) was investigated in varieties of L. esculentum. It varies in disposition from size of a single macrochromomere of heterochromatin to a heterochromatic rod 13.5 u in length. The achromatic region separating the satellite from the other heterochromatic portion of the chromosome is also quite variable, ranging from a very short gap to one of 5 u in length. The lengths of the satellite and of the achromatic segment are not correlated. Most of the rest of the genome is similar in these varieties.
Combining ability of different backcross generations.
Honma, S., and T. M. Currence^1^
Tomato geneticists might be interested in the results of an attempt to add three recessive genes, potato leaf c, green stem a, and positional sterile ps, to the variety Firesteel. Potato leaf is located in linkage group IV; green stem in V; and positional sterile in I.* Selection for the three characters and backcrossing to Firesteel has been carried through four backcrosses. Because of sterility the material was tested by using it in crosses. A selection saved from the F3 of the first cross and from each backcross therefore has been tested for combining ability against the combining ability of the recurrent parent, Firesteel, and of the non-recurrent parent NC-1-48 F3. Each selection and both parents were crossed with four testers namely, Break O' Day, Bounty, Table Talk, and Stemless Pennorange, and 60 plants from each cross were grown in a triple lattice design with six replications. A total of 240 F1 plants were therefore grown as hybrid progenies of each selection and of each parent.
Graphs are used to show the fruit size and yield data obtained. Results are given in per cent of Firesteel. Firesteel therefore was rated as 100 and the means giving the curves were converted to percentage of comparable Firesteel means. The broken line in Figure 1 shows yield data. NC-1-48 F3, the non-recurrent parent selfed once was 86 per cent of Firesteel for total yield. The F3 of the original cross was slightly but not significantly superior to the recurrent parent. Recovery of Firesteel combining ability was therefore indicated at this point, but declined as the backcrossing program advanced. A possible hypothesis is that genes of groups I, IV, and V have an important relation to the favorable combining ability of Firesteel. It is apparent that by eliminating the dominant alleles of ps, a, and c from the Firesteel genome as represented by the fourth backcross, there was a loss in transmitting yield. This assumes selecting for whole chromosomes since crossing-over and linkage could not be de-
Figure 1. Combining ability of backcross lines in percentage of Firesteel, the recurrent parent.
tected in the material. The fact that the loss did not occar sooner in the program can possibly be explained by postulating an interaction. Such interaction would need to be between genes from each parent and limited to that part of the genome not affected by selection. As backcrossing advanced, there was elimination of that part of NC-1-48 F1 genome unaffected by selection and by such loss there was disappearance of the interaction that gave the favorable combining ability. It would seem then that the backcrossing program was not successful in retaining Firesteel yield genes while adding three sample recessives to the variety.
In fruit weight of their hybrid progenies the non-recurrent parent was 91 per cent of Firesteel and therefore significantly smaller. As shown by the solid line the first, second, and third backcrosses were slightly but significantly superior to Firesteel. The fourth backcross did not differ significantly from the recurrent parent and probably should be considered its equivalent. From this behavior, dominant alleles of the recessives that were selected from each cross did not have much relationship to the Firesteel genotype for fruit weight. The first three backcrosses being superior to the recurrent parent can be assumed to result from an interaction involving that part of the genome unaffected by selection. With elimination of those coming from the non-recurrent parent, Firesteel ability to transmit size was approximated and was not lost in the backcrossing program as occurred for yield.
* Correspondence with R. E. Larson, Penn. State College.
1 Paper No. 2929 of the Scientific Journal Series of the Minnesota Agricultural Experiment Station.
Kemp, G. A.
Tomato production in southern Alberta has been seriously limited by a short frost-free period. It is felt that the development of resistance to several degrees of frost especially in the spring may add ten days to two weeks to the producing period. A large number of accessions have been secured for this purpose including wild species and species crosses from the U.S.D.A. P. I. Station, Ames, Iowa. In addition, a number of tomato accessions which have already withstood some frost including G-1393 from Dr. P. A. Young have also been grown. Although this material was planted in the field in mid-May of 1952 frosts which normally occur at that time failed this year. Special attention is being directed to L. peruvianum and crosses between L. peruvianum and L. esculentum as promising sources of this character.
An environmental effect on the ps gene.
Kerr, E. A.
The gene for vase-shaped flowers (ps) with its attendant functional sterility is being transferred by backcrossing to a variety (B-121) which is immune from Cladosperium fulvum. This variety was derived from the cross Vetomold x L. hirsutum.
In the spring of 1952 one plant of two ps ps lines and our plants of a Ps ps line were grown (seed planted 29 Nov. 1951) transplanted to beds 21 Jan. 1952). The flowers on the two bottom clusters of all these plants lacked the adhesion of the petals to the staminal cone which is characteristic of ps ps plants. Two plants of the heterozygous line were removed after the first flowers opened. Beginning at the third cluster the plants of the homozygous lines and one of the plants of the heterozygous line bore vase-shaped flowers. No fruit set on the lower clusters of the ps ps plants although fruit set freely on the bottom clusters of the remaining plant of the segregating line. In the fall of 1952, flowers of ps ps genotype had the characteristic adhesion until about the middle of November. Thereafter the adhesion was not as tight as usual and occasional petals and flowers were spread as in the Ps genotype. It is probable that this effect is caused, in part at least, by short day-length or low light-intensity.
Observations on Lycopersicon peruvianum crosses.
In a family of L. peruvianum (P. I. 128657) consisting of twelve plants two were aberrant, i.e., 49/1-3 and 49/1-12 (Hereditas 36:509, 1950). The former had apparently normal flowers but the pollen grains were empty. Aberrant plant 49/1-12 had green corolla. A normal plant (49/1-9) pollinated by 49/l-12 gave plenty of seed. Fifty F1 plants of this cross were raised in 1952. Of these 35 were normal and 15 mutant. The mutant plants were completely sterile, and had large, leafy, rather branched inflorescenses. In the flowers of the mutants the calyx was abnormally large and leaf-like. Similarly the corolla was often green and leaf-like. The pedicle joints were poorly developed or absent. The anthers showed several kinds of abnormalities and were sometimes entirely absent. Somewhat more normal flowers appeared in the autumn.
I have found that self-incompatibility in L. peruvianum (P. I. 128657) and L. peruvianum var. dentatum (P. I. 149033) is determined by oppositional alleles. Intervarietal crosses have been performed reciprocally using four plants from each of these populations. Seed was obtained only when L. peruvianum was used as the pistillate parent, and only three F1 hybrids were obtained from the 90 pollinations made in this direction. These intervarietal combinations thus appear to show a remarkable degree of incompatibility.
The F1 hybrids were diploid. One was dwarf and prostrate with small flowers. Dwarfs have been observed by Soost and Lesley (TGC Report No. 2, 1952) in crosses involving L. p. dentatum. The remaining two F1 hybrids were tall and vigorous. One of them had 53% empty pollangrains. In contrast to L. p. dentatum, tha F1 hybrids and L. peruvianum were resistant to root knot (Heterodera marioni). Some races of L. p. dentatum may be successfully crossed with diploid L. esculentum as the pistillate parent. However, this was not the case with the strain used in these studies (P. I. 149033).
At Alnarp in southern Sweden plants of this vigorous L. p. dentatum population produced much seed probably by insect pollination. According to Lesley (Econ. Bot. 2:105, 1948) L. p. dentatum at Riverside, California, is a weak grower, which flowers only at intervals and rarely sets seed.
ps linked to d\1\(d) in the first linkage group.
Larson, R. E., and B. L. Pollack
In an attempt to determine the linkage relationship of ps ps as described by Larson and Paur, F2 and BC tester populations were field grown at State College in 1951 and 1952. In each case a large deficiency of mature dwarf plants (d\1\ d\1\) made the data unreliable. The data did suggest however, a possible relationship of ps with d\1\. To investigate this possibility F2 and BC populations were grown in the greenhouse where more control could be maintained ever the plants. Six plants from a F2 population of 841 and two plants from a BC population of 248 failed to reach maturity. The data indicate that ps is linked with the d\1\ in the first chromosome. Linkage values of 8.5 +\- 0.12% and 6.91 +\- 1.61% were obtained from the F2 and BC populations, respectively. Three point tests are in process to determine the relationship of ps with other genes in group I.
Chi-Square Values for F2 Population (repultion) _________________________________________________________ X^2 p _________________________________________________________ Dd seg. 2.0124 .10 - .05 _________________________________________________________ Ps ps seg. 2.2455 .10 - .05 _________________________________________________________ Linkage 60.2699 < .01 _________________________________________________________ goodness of fit 64.5278 < .01 _________________________________________________________ Linkage value = 8.5 +\- 0.12%(Owens Max. Liklihood Method) _________________________________________________________ Chi-Square Values for Backcross Population (repulsion) _________________________________________________________ X^2 P _________________________________________________________ Dd seg. 0.146 .95 - .50 _________________________________________________________ Ps ps seg. 0.585 .50 - .20 _________________________________________________________ Linkage 182.699 < .001 _________________________________________________________ Goodness of fit 183.430 < .001 _________________________________________________________ Linkage value = 6.91 +\- 1.61%Fruitfulness and fertility of tetraploid interspecific hybrids.
Lesley, J. W. and Margaret M. Lesley
A tetraploid hybrid of diploid L. esculentum and L. peruvianum var. dentatum occurred in F1 without controled pollination; it was more fertile than its diploid sibs and partly parthenocarpic. After two generations of backcrossing to L. esculentum 4 n and three of selfing, a tetraploid hybrid occurred that was 100 per cent fruitful, totally sterile, and parthenocarpic. The microspores and megaspores were abortive. Parthenocarpy was spontaneous or non-stimulative. The female parent of the original cross and two backcrosses was L. esculentum. A sib of this tetraploid hybrid was more fruitful and much much fertile than autotetraploid Pearl Harbor. No difference was found in meiosis in the pollen mother cells of autotetraploids and the tetraploid hybrids. The increased fruitfulness and fertility appear to be due to favorable gene combinations resulting from species hybridization and recombination. The extraordinary fruitfulness of the parthenocarpic tetraploid hybrid suggests increased hormone activity. The fruitfulness of heterosis may depend on a similar activity also caused by a favorable combination of genes.
Further researches on the gene t governing the synthesis of prolycopene(submitted by C. Jucci)
In the F2 of the "tangerine x Palla Oro" a new phenotype appears, a yellow tangerine, in which the the chief carotenoid pigment is prolycopene.
If yellow tangerine is rr tt as appears most probable (notwithstanding to be sure it is necessary to backcross with Palla Oro, in order to discriminate the Rr tt genotype) and in agreement with the experiences of Jenkins and Mackinney at Berkeley and of Butler at Toronto, the gene t is capable of giving its peculiar effect also in absence of R so could scarcely be considered a modificator of the effects of R. The synthesis of the two stereoisomers probably, therefore is effected through different biochemical paths. This conclusion would be in agreement with the results of experiences of ripening under high temperature (35 - 36 deg.). These enhance the synthesis of beta-carotene and of prolycopene while they inhibit the synthesis of lycopene.
It is presumable that the physiogenetic analysis of these genes, especially deputed to the biosynthesis of such stereoisomers, could throw light on the physiological value of these natural polienes and help to discover their precursor.
Genetic analysis of the F3 in the cross L. esculentum x L. hirsutum. Selection of tomatoes with high content of both vitamin C and a provitamin. (submitted by C. Jucci)
Physiogenetics studies on the caro- tenoid pigments in tomatoes are extended to new varieties and lines.
No correlation is found in several tomato varieties between carotenoid and vitamin C content. In fruits ripened at high temperature, also in lines having high Beta-carotene, the biosynthesis of the pigment keeps normal while lycopene biosynthesis is blocked.
Similar behaviour occurs in the F3 progeny of some L. esculentum x L. hirsutum; the gene B is not to be considered therefore as modificator of the gene R.
Variability curves for Beta-carotene and for lycopen biosynthesis in this F3 progeny show analogous behaviour of the two genes: both R and B are present in the hirsutum parent, but they do not reveal themselves, neither in Fl, because their effect is blocked by a number of inhibitor genes having additional effect and dominant. The gene B is not present in the ordinary red strains; if present must be together with the set of inhibitors.
Experimental results and bibliographic data agree in showing that new lines characterized by high content both of provitamin A and vitamin C could be selected from L. hirsutum x L. pimpinellifolium and from backcrosses of it with high carotene lines or crosses between such lines and L. pimpinellifolium.
On F3 Comet x hirsutum only one strain has high Beta-carotene content (4.52%) and vitamin C content (mgr. 40%) like these of ordinary trade varieties. New lines with equal content of the two pigments, lycopene and Beta-carotene, appear in the F3 esculentum x hirsutum.
Physiogenetic researches on some genes governing the flesh pigmentation in species of Lycopersicon. (submitted by C. Jucci)
Biochemical researches on Fl and F2 hybrids of the L. pimpinellifolium x L. esculentum and L. hirsutum x L. esculentum have been performed.
A peculiar gene (B) - and not a pleiotropic affect of the same gene R affecting lycopene synthesis - appears resporsible for the Beta-carotene synthesis.
In F2 hybrids L. esculentum x L. hirsutum some of the descendants show a high Beta-carotene content.
This fact is very interesting also for agricultural application since selection is possible of new varieties endowed of very high provitamin-A content.
Analysis of Fl hybrids with tangerine varieties fails to show peculiar behaviour, but demonstrates a genotype TT both in yelLow (Palla Oro) and in red varieties.
High temperatures (35-36 deg.) promote the synthesis of Beta-carotene and of prolycopene and inhibit lycopene synthesis, while low temperatures (5-6 deg.) inhibit the synthesis of every pigment and even the normal disintegration of the chlorophyll.
Alteration of high (36 deg.) and low (5-6 deg.) temperatures does not seem to promote a larger synthesis of the pigments: that seems the case, however, for an alternation of high (36 deg.) ones and temperatures little lower (20-25 deg.) than normal.
A stem fasciation.
Martens, T. R.
Individuals exhibiting a marked stem fasciation, designated as rosette by A. B. Burdick, are being studied in order to ascertain the mode of inheritance of the trait. These plants are individuals segregated from the F3 and F4 of a cross between Waltham Forcing and the d, d\2\ (dm)f lf j H a\2\ (al) wt tester. The rosette strain carries j, lf, wt, and f homozygous.
Associated with the stem fasciation and perhaps an index to it, is a modification of the position of the first inflorescence. Normally appearing in the interval between the seventh and twelfth leaves, the first inflorescence in the rosette plants occurs as a termination of the main axis at the twenty-second node, on the average.
Furthermore, at the usual height of the first inflorescence axillary branching occurs, producing lateral branches (two or three in number) of a size comparable to the main axis. The large, fasciated, terminal fruits and the fleshy, thickened stems are so heavy that frequent breaking occurs.
Plants grown at a constant temperature of 60 deg. F. markedly express the trait, regardless of photoperiod. Plants grown at 80 deg. F. show the trait to a lesser extent. A thorough study of the relationship of photoperiod and temperature to the expression of the rosette trait is being planned. The completion of the preliminary physiological and genetic investigations is expected by June, 1953.
Natural cross-pollination among cultivated tomatoes in Mexico.
Richardson, R. W., Jr.
An observation plot of commercial tomato varieties was set out January 1952 at Jaloxtoc, the winter breeding station in the State of Morelos. This station, at an elevation of 4100 feet is frost-free the entire year and normally receives no rainfall for a period of seven months from October to May.
Shortly after flowering began considerable insect activity was noted, and preliminary notes were taken on the rate of natural cross-pollination occurring in this field. Insects were collected and representatives have been identified as Augochloropsis ignita (Sm.) of the family Halictidae.
The planting was designed primarily as an observation plot with two replications, rows at two meters and plants spaced one meter in the rows. Two potato-leaved varieties in trial, Red Jacket and a native commercial called Hoja de Papa were selected to provide a rough measure of cross-pollination. Fruit were harvested from two, ten plant plots of each variety at regular harvest intervals. In no case were any two plots with potato-leaf type closer than 20 meters. Seed from each harvest date was sown and counts made of seedling leaf type. All normal, cut leaved seedlings were assumed to result from cross-pollination since potato-leaf type is a recessive character.
A season's average of 10.86 per cent of cross-pollination was observed for Hoja de Papa and 12.01 per cent for Red Jacket. It is seen in the accompanying table that rates varied considerably with date of harvest, ranging from a low of 5.74 per cent in fruit harvested April 2 to a high of 16.92 per cent April 14.
Since individual plant data were not recorded it is not known what influence spacing may have had on the results observed. Plants at the ends of each plot were adjacent and closer than any others to cut leaved plants and may have had a different rate of cross-pollination.
At this time the cause of differences in rates observed at different harvest dates are not known. It is thought that they may represent variations in insect activity or fluctuations in insect and flower populations.
Percentage of Natural Cross-pollination in Tomato Varieties
Hoja de Papa and Red Jacket H0JA DE PAPA ________________ Percentage Date of of cross- harvest cc C- TOTAL pollination _________ ____ ___ _____ ___________ 26-III-52 1181 151 1332 11.33% 2- IV-52 2036 124 2160 5.74% 9- IV-52 1252 127 1379 9.21% 14- IV-52 1517 309 1826 16.92% 23- IV-52 1970 296 2266 13.06% 30- IV-52 2381 253 2634 9.60% _________________________________________ TOTAL 10337 1260 11597 10.86% RED JACKET _____________ Percentage of cross- cc C- TOTAL pollination _________ ____ ___ _____ ___________ 26-III-52 1379 118 1497 7.88% 2- IV-52 2526 288 2814 10.23% 9- IV-52 1555 285 1840 15.48% 14- IV-52 3051 251 3302 7.60% 23- IV-52 3413 468 3881 12.06% 30- IV-52 4148 783 4931 15.88% __________________________________________ TOTAL 16072 2193 18265 12.01%New male-sterile mutants.
Rick, C. M.
Heretofore male-sterile mutants (in the strict sense) were obtained here in the varieties Early Santa Clara, Pearson, and San Marzano. With the five described herewith this list is broadened to include Pritchard, Earliana, Ace, and Cal 255. In each of the new mutants only the production of normal pollen is affected; the plants seem to be normal in all other aspects.
According to the following table each of the five behaves as if determined by a single recessive gene, thus conforming to the pattern of the previously described 13 mutants. In all mutants the recessive segregants are deficient, but in no case is the deficiency significant at the 5% level. The consistent deficiency possibly represents a slight reduction in the viability of the mutants.
Inheritance of male-sterility _______________________________________________________ Mutant F2 Backcross ____________________ _____________________ Observed Expected Observed Expected ________ ________ ________ _________ + ms + ms + ms + ms ___ ___ ___ ___ ___ ___ ___ ___ ms\14\ 60 11 53.25 17.75 170 152 161 161 ms\15\ 35 5 30 10 10 10 10 10 ms\16\ 146 128 137 137 ms\17\ 31 23 27 27 ms\18\ 25 24 24.5 24.5Each of the mutants is described briefly as follows: (2-175) var. Earliana. Anthers are markedly paler than normal, corresponding rather closely to the color of the corolla; they are of normal length but are collapsed and thinner. Stigmas are generally held below the level of anther tips, but due to the fasciation of the flower parts, the stigmas are usually exposed sufficiently to permit easy pollination. The small amount of material that can be prodded from the anthers with a needle proves to be 100 per cent aborted pollen. The grains are uniformly large, betraying degeneration in late microspore development. Meiosis appears normal at all stages. This is the mutant used by Larson (Proc. A.S.H.S. 56:358-362, 1950). Seed yields do not give any indication of reduced ovule fertility.
ms\16\ (2-193) var. San Marzano. Although this variety is well represented in our collection of ms mutants, this new mutant was added because its extreme reduction of anthers should make it desirable for ease of large-scale pollination. It is easily the most extreme mutant we have yet seen. Anthers are very pale, almost tending to be greenish; they are very shrunken, spread widely below, are attached only at their tips, and permit the stigma to be well exposed. As proved by the appropriate test crosses it is not allelic with ms\5\ or ms\10\, the two mutants that it phenotypically resembles most. Development of anthers has not been studied in this mutant, but it seems likely that the sporogenous tissue degenerates before meiosis. Seed yields of the recessive type are normal.
ms\16\(LA-62) var. Pritchard. This mutant was acquired in 1947 from Dr. Oscar Pearson and is the one that was used recently by Bullard and Stevenson in studies of hybrid seed production at Purdue. Flowers appear to be of normal size. Anthers are noticeably paler than normal and only slightly darker than the corollas; they equal or slightly exceed the style in length, but under our conditions the tips recurve slightly so that all but a small proportion of the flowers have exposed stigmas. Under most conditions the anthers yield no pollen or aggregated masses of pollen aborted in early stages, yet in the late summer of 1952 anther smears revealed 20-32 per cent stainable pollen, that mostly looked normal. As grown under isolation for several years plants of this mutant have never produced fruits with seeds except after pollination. Seed yields do not likely indicate any reduction of ovule fertility.
An interesting aspect of the history of this mutant at Davis is the appearance in the field in 1950 of indeterminate plants, which segregated for male sterility as well as their determinate sibs. By mating only determinate plants this situation was corrected so that the line now being used is as entirely determinate as the parent var. Pritchard. Considering the genetic behavior it seems most likely that a mutation back to the dominant or indeterminate condition occured in this line.
ms\17\ (2-225) var. Ace (recent introduction by the Campbell Soup Co.) Flowers appear to be about of normal size. Anthers are paler in color than normal but slightly darker than the corolla. They are slender but still exceed the style considerably in length so that the stigma is seldom exposed for easy pollination under our conditions. Although a tiny amount of white material can be prodded from the anthers with a needle, microscopic examination reveals no pollen in any condition present in the anthers. All stages of meiosis have been seen and are apparently normal; degeneration is evident in the tetrad stage. Seed counts reveal normal or nearly normal ovule fertility.
ms\18\ (2-233) var. Cal-255 (late canning variety developed by G. C. Hanna). Flowers are about normal in size. Anthers are slightly paler than normal and are slighty shorter but very much more slender than normal. Anther tips tend to wither, thereby exposing stigmas of 80 per cant or more of the flowers, Anthers tend to separate from each other throughout their length. Prodding with a needle fails to dislodge any material from the anthers. Smears reveal no pollen nor vestiges of pollen in mature anthers and degeneration mostly at diplotene in younger anthers. It is rather difficult to induce fruits to set on this mutant and the seed count is low (mean= 43 per fruit ), suggesting ovule sterility or some other defect in the gynoecium.
These male-sterile mutants have been picked up as unfruitful plants in nearby fields in October at the rate of about two or three per afternoon. During these searches we always encounter, especially in the var. Pearson, a wealth of other floral defects -- characters that almost invariably have later demonstrated recessive monogenic determination. Being limited in the amount of time and space that can be devoted to such material, I pass up most of this material. This matter is mentioned here in case any member might like to acquire some of this new material for his own research or that of students. I would be very glad to collect seed of such items for anyone who might express an interest in them. It should also be pointed out here that I do not intend to make a systematic test for linkages of these new male-sterile mutants.
Recent work with the trisomies.
Rick, C. M.
During the past season the only new linkage established was that of mc. Good trisomic ratios were obtained for mc in the cross with a line trisomic for chromosome 7, which has already been shown by trisomic tests to carry wt.
Don Barton and I are confident that we have obtained all twelve primary trisomics, and we are in the process of preparing our data for publication. Until descriptions of the types and other data appear in print, research notes on this material will not be very meaningful. We also hope to have sufficient seed for exchange by that time.
Tests of compatibility of certain stocks of L. peruvianum var. dentatum.
Rick, C. M.
The tests to be reported here largely concern the following three lines of L. p. var. dentatum:
1. PI 128,660
2. Collection No. 30349 of Goodspeed's Expedition of 1942.
3. A collection that I made at Moquegua, Peru in 1949.
Crosses between these three lines are fully compatible, yielding a large fruit with 50 or more seeds apiece for nearly every flower pollinated, yet they cross with great difficulty, if at all, with our other lines of L. peruvianum. During the past two seasons test crosses were made in the greenhouse between the first two listed above and 15 lines of L. peruvianum and L. glandulosum. Reciprocal crosses were made of most combinations. The data of glandulosum crosses are included because this "entity" behaves like peruvianm in its compatibility relations. Of some 283 flowers pollinated nearly all set fruit. About half the fruits were seedless, the remainder containing 1-12 seeds apiece, the seeds being quite variable in appearance, some being subnormal in size, others larger than normal. Germination was attempted unsuccessfully with some of the seed lots; other lots germinated, but gave rise to plants that obviously were not hybrids. The mean level of seed production was no higher than in crosses between the same peruvianum stocks and L. hirsutum -- another cross which so far has not yielded a single F1 hybrid. It seems very likely that under our conditions a slight amount of pollen drift in the greenhouse could account for the presence of seeds in fruits of incompatible crosses and also of flowers that have not been pollinated. Control sib crosses in all of these lines gave fruits with 40-50 or more seeds each.
Not only do these three lines differ sharply in their compatibility relations from other stocks of L. peruvianum, but they can be distinguished from them also in the following morphological features: (1) Tendency toward a more erect habit with stems that are heavier and more brittle. (2) Peduncles, especially of the first inflorescences tend to be very long. (3) The number of larger leaf segments tends to be greater than in other stocks of peruvianum, but this does not hold for line No. 3.
The differentiation, both in respect to compatibility and morphology seems quite significant and might warrant revival of the old specific name, L. dentatum or chilense. The name L. p. dentatum (as applied by Muller) covers this entity but also includes many other-collections of L. peravianum that do not agree in either compatibility relations or morphology with this group. In other words, this group falls within the rather nebulous L. p. dentatum according to the latest taxonomic treatment, but differs as indicated from other components within it.
Crosses to L. esculentum have been attempted extensively only with line No. 2, which, unfortunately is represented in our collection only by the clone of a single seedling. Up to the present time 5 hybrids have been obtained, two of which are with var. Pearson, the rest with other lines of L. esculentum, all being obtained via embryo culture. The crossing is somewhat easier than with typical L. peruvianum, but still requires searching hundreds of fruits for the larger ovules. But in backcrossing to L. esculentum, the difference is even greater, for we can get roughly 5-8 seedlings per fruit without culturing against almost no yield from hybrids with typical peruvianum. It seems very likely that PI 149,033 reported in Dr. Lamm's research note belongs with this group, which is also reminiscent in some respects of the line of dentatum which Dr. and Mrs. Lesley studied extensively.
The use of growth-promoting substances as an aid in tomato breeding.
Rick, C. M., and Dora Hunt
Crosses between certain lines of tomatoes, particularly the species, are difficult under any conditions, and during parts of the growing season here crosses in the field are difficult with any material. The common difficulty under these situations is that, after pollinations the flower dehisces without setting fruit. Following the success of Emsweller in his use of auxins in lily breeding a small test was executed here with tomato material.
Three mutants of San Marzano were selected for this study: ms\10\ an extreme male-sterile that never sets fruit unless cross-pollinated: pi, a mutant that has very badly deformed flowers and is notoriously difficult to cross: and 2-109, a mutant with slight deformaties that presents a moderate problem in cross-pollination. The male-sterile mutant was growing in good isolation from other tomatoes, the other material was surrounded by fertile plants in the main planting.
The treatments applied included: one per cent indolebutyric acid in lanolin (a fruit-set aid that has been used by many workers), concentrations in the range of 0.005 to 4.0% p-chlorophenoxyacetic acid in lanolin, 0.005% and 0.01% of the sodium salt of CPA acid in water. All treatments to ms\10\ except controls were applied without pollination. All treatments to the other mutants were accompanied with pollination with pollen of known good viability.
The following relations were observed. Concentrations of O.05% or higher of CPA in lanolin and of 0.005% or higher in water induce parthenocarpy in unpollinated flowers and are therefore undesirable as aids in breeding. Furthermore, in pollinated flowers of the 2-109 mutant the mean seed count decreased with increasing concentrations until, at 4% CPA in lanolin, few fruits are set and these are all parthenocarpic. The water and lanolin applications at lower concentrations improved the fruit set of the 2-109 mutant from ca. 35% to 70% thereby increasing the seed yield per flower pollinated to about twice that obtained by control treatment (pollination without hormone application). No treatment gave better seed yields per fruit than the control, although the lower concentrations apparently did not decrease seed yield levels.
The mutant pi proved unsatisfactory because flowers varied greatly in form and were inadequate in numbers. All treated and control flowers of this mutant failed to set.
On the basis of these results, preparations of 0.005 and 0.01 per cent CPA in lanolin are standard items in our field equipmnt and they are applied to flowers in nearly all crosses. Lanolin was adopted instead of water as the vehicle for the CPA because it is easier to apply, it provides a more stable medium, and a sufficient residue usually remains to mark the treated flowers. The effectiveness of crosses has been so greatly improved that crosses of almost any lines are achieved under field conditions. During the past season it has meant that at least 80 per cent of the projected crosses succeeded in the first attempt, usually consisting of only four or five flowers per cross. The same concentrations were applied to selfed flowers of L. peruvianum and its F1 hybrid with L. esculentum in an attempt to break the self-incompatability. Although many fruits set, they were all parthenocarpic.
New Seedling Characters.
Robinson, R. W., and C. M. Rick
These five characters are useful in genetic studies because classification is very good in early seedling stages. The three chlorophyll deficiencies have been hybridized and proved to be non-allelic.
rv (reticulate virescent) LA 54. Obtained from G. C. Hanna as a mutation in his line 45-116-4. Cotyledons are pale green in color and noticeably narrower and smaller in total dimensions than normal. The venation of the leaves and cotyledons of the seedling is darker than the rest of the blade, and this difference is expressed even when the seedling is heterozygous for Xa. Virescent seedlings grow very much more slowly than normal seedlings, presumably because of a deficiency of chlorophyll. Plants grown in the greenhouse have light green leaves reticulated with dark green veins, not changing much with age, but plants grown in the field have dark green leaves without the distinct venation characteristic. Leaves of greenhouse-grown plants remain smaller and have a characteristic ragged edge. In the field plants grow rapidly after they become green but do not set many fruit because of a high degree of pollen sterility. Seeds can be obtained if rv is used as a female parent. Segregation in the F2 is significantly different than the expected 3:1 apparently because of reduced viability, the F2 segregation being 2057:358. A deviation in the direction of linkage was indicated in the F2 of the repulsion cross with r but the deviation was significant only at the O.10 level.
yv (yellow virescent) LA 55. Appeared as a second mutant in an asynaptic line (2-94). At any stage of growth, whether in field or greenhouse, cotyledons and true leavas first appear yellowish, later becoming more greenish. In the greerhouse older leaves always remain distinctly paler than normal but in the field they turn to a normal color and the plant is otherwise normal in size, vigor, and fruitfulness. Despite weak growth, plants in the greenhouse can be induced to produce fruits and seeds. The cotyledons of yv plants are uniformly colored and therefore easily distinguished from rv. Segregation in the F2 was 2141:603, a significant deviation from expected. yv is not linked with any marker gene thus far tested.
dv (dwarf virescent)LA155. Appeared an breeding line 220-17-8 of G. C. Hanna. dv are easily distinguished from rv because they do not have distinct venation and from yv because they have a slower rate of growth and change from yellow to green more quickly than yv seedlings. Mature dv plants are dwarf in habit under any condition. Unlike yv, the growing point of mature plants is green in color. The plants are relatively fruitful under most conditions although the seed yield is low. dv is located on chromosome one, where it is very tightly linked with m and d. It also shows linkage with Wo. Segregation in the F2, 1468:340, is less than expected, presumably because of reduced viability.
ct (chicken foot) LA64. Obtained in 1948 from Dr. 0. Shifriss, W. A. Burpee Seed Co. as inbred No. 5701-9-3-4. This gene affects shape and size of all true leaves without much environmental variation. The first true leaves appear much narrower and more entire than normal and differ from normal in a peculiar, yet rather intangible texture. Leaves above the fifth position are usually split into three narrow lobes at the end of a very long rachis, occasionally a few additional lobes appearing. Plants tend to branch sparingly, internodes are short and the plant has a distinctly upright habit. Pedicels and peduncles are somewhat shorter than normal. Without artificial pollination this mutant is rather unfruitful. It is refractory for hybridization in the field, but crosses can be made very readily in the greenhouse. This mutant agrees closely in morphology with tf, described by Dennett, Pollack, and Larson in this Report but differs in its higher pollen fertility, homozygous ct having 80-95 per cent viable pollen, the heterozygote having 80-98 per ce-nt. The gene ct was found to be linked with wt but did not show linkage with the lf-j which Butler (Jour. Hered. 42: 100-104,1951) reported is linked with wt. Segregation in F2, 1940:659, does not differ significantly from 3:1.
dl (dialytic anthers)2-69. This mutant was described by Rick (Amer. Nat. 81:185-202, 1947). dl plants can be classified in the seedling stage by the suppressed hair development. dl shows linkage with l, but the deviation is significant only at the .05-.10 level. Segregation in F2 was 1756 normal; 500 dialytic.
All F2 linkage tests conducted to date are summarized in the following table.
Tester Gene: dl ct rv Wo m d r y c a lf-j l H Xa al wt Linkage groups I I I II III IV V V VI VII VII VIII X dl - x x x x x x x x ** x x ct x - x x x x x x x x x ** rv x - x x x * x x x x x yv x x x x x x x x x x dv x x ****** x x x x x x x* indication of linkage, but deviation significant only at 10% level.
** significant indication of linkage at 1% level.
x no linkage.
Dosage effects of Wo in trisomics, triploids, and tetraploids.
Soost, R. K.
Progeny resulting from selling tetraploid Wo plants show four viable phenotypic classes in regard to the "wooly" appearance of the foliage. These four classes increase in expression of the character from non-wooly to extreme wooly. It seems likely that these four classes correspond to the four genotypes, +/+/+/+ (non-wooly), Wo/+/+/+ (very slightly wooly), Wo/Wo/+/+ (wooly), Wo/Wo/Wo/+ (very wooly), with the fifth expected class Wo/Wo/Wo/Wo being non-viable. A few of these plants have germinated but have failed to grow beyond the cotyledon stage. It is hoped that sufficient progeny can be obtained from each viable phenotype so that each genotype can be determined.
Trisomic plants with one dose of Wo have been produced. They appear slightly less wooly than diploid heterozygous Wo plants and preliminary counts indicate a lower pertentage of branched hairs. To date no plants have been identified in the progeny of these trisomics which have been Wo/WO/+ in genotype.
Appropriate crosses have failed to give triploids.
A chimera which resulted from the colchicine treatment of Wo/+ diploid seedlings was in part Wo/+ diploid. The other section is much less wooly and is tetraploid. No progeny have been obtained from this section. Since this happened to be the first tetraploid studied it was originally reported (TGC Report 1952) that the expression of the Wo gene in the tetraploid Wo/Wo/+/+ was less wooly than the diploid Wo/+. Additional tetraploids have been phenotypically as wooly as the Wo/+ diploid. The genotype of this less wooly section of the chimera remains determined.
Counts of the trichomes have shown that while diploid, trisomic, and tetraploid plants have differed in numbers of trichomes the wooly plants of each class of ploidy have not differed from the non-wooly plants in trichome numbers but show an increase in the number of trichomes which are branched. The increase in the wooly appearance of the four tetraploid phenotypes is accompanied by an increase in the number of trichomes which are branched and an increase in the number of branches per trichome.
La resistencia de progenies de Lycopersicon hirsutum por variedad Panamerica a Phytophthora infestans y a una enfermedad de virus.
deZerpa, Dora M.
Una linea de Lycopersicon hirsutum introducida en 1949 por a Facultad de Ingenieria Agronomica (Venezuela), resulto ser inmune a Phytophtohra infestans, en condiciones de campo durante una estacion lluviosa en Caracas.
La misma linea demostro resistencia a una enfermedad virosa muy conmun en los cultivos de tomate que posee sintomas identicos al "leaf curl."
Como consecuencia de este comportamiento se realizaron cruzanientos entre este tomate silvestre y la variedad comercial Panamerica con el objeto de pasar la resistencia de L. hirsutum a una variedad comercial.
Las siete plantitas obtenidas crecieron vigorosamente y comenzaron a florecer y fructificar en ambiente de laboratorio, Los frutos obtenidos no contenian semillas, pero esta esterilidad desaparecio cuando las plantas fueron llevadas al campo.
Estas plantas de F1 han sido mantenidas desde 1950 hasta la actualidad, mediante propagacion vegetativa y sometidas en condiciones de campo a dos estaciones lluviosas, epoca en que Phytophthora infestans.es muy activa. Las plantas no sufrieron el ataque de la enfermedad y no se observo en ellas las manchas caracteristicas del hongo.
Durante las estaciones secas, en que la enfermedad de virus hace estragos en los cultivos de tomate, no hubo en las plantas de F1 sintomas visibles de la enfermedad, a pesar de estar infectadas todas las variedades comerciales que crecian junto a ellas.
La F1 de L. hirsutum por Panamerica es sin duda resistente a ambas enfermedades, pero el tomano del fruto es muy pequeno. Con el fin de aumentar su tomano se hicieron retrocruzas sobre Panamerica y las plantas de R1 obtenidas se probaron en la estacion lluviosa y mediante inoculaciones artificiales. Unos pocos pedigrees mostraron alguna resistencia a Phytophthora.
Algunas de las plantas de Rl sembradas en la epoca seca no contrajeron la enfermedad de virus y sobre estas se hicieron segundas retrocruzas con Panamerica, suponiendo que su sanidad se debia a verdadera resistencia; las cuales estan en este memento cultivadas en estado de plantulas.
English summary. A line of L. hirsutum was found to be immune to Phytophthora Infestans and also resistant to a virus disease with symptoms identical with "leaf curl". F1 hybrids between this collection and L. esculentum v. Panamerica showed no symptoms of either disease under conditions in which all susceptible plants were infected. Plants of the first backcross to Panamerica segregated for resistance to both diseases. Resistant plants were mated to Panamerica for a second backcross, which is now being tested.