Avdeyev, Y. I. The lethal mutant of tomato.
A spontaneous lethal mutation related to ala/alb-type mutants has been discovered in the variety Shtambovy
Malinovy.
The germination of mutants is normal. The mutants cease growth after the appearance of cotyledons, which
at first have normal green color but turn to yellow and white, starting in the middle of the lamina. The first and
second true leaves emerge without chlorophyll and the plants wither 15-17 days after germination.
The segregation observed in var. Shtambovy Malinovy was 141 mutants and 412 normal plants,
corresponding to a theoretical 3:1 ratio (X2 = 0.074) with an associated probability of 0.95 p 0.75. The mutant shows
heterosis for early yield. The F1 exceeds the normal homozygote in total yield by 10.4%, in the first harvest by
25.7%, and in red fruits of the first harvest by 59.2%. Differences in size of plant and in mean weight of fruit do not
exceed 2%.
Cirulli, M., and F. Ciccarese Influence of light intensity on the phenotypic expression of Tm genes.
The type of reaction of tomato to the Tobacco Mosaic Virus (TMV) depends on the resistance genotype of
the host and the virulence genotype of the pathogen. However,. environmental factors may condition the expression
of tomatoes possessing Tm genes. It has been reported by Cirulli and Alexander (1969) and by Cirulli and
Ciccarese (1975) that Tm genes are temperature-dependent. In the course of our studies on TMV resistance of
tomato we found that factors other than temperature can also affect the reaction of Tm genes to TMV. Results are
reported here on the influence of light intensity on the tomato/TMV system. Tests were carried out in the
greenhouse at 26oC. Three light conditions were tested: I) reduced greenhouse light (7,000 lux at 11 a.m.); 2)
normal greenhouse light (14,000 lux at 11 a.m.); and 3) normal greenhouse light plus supplementary artificial light
(30,000 lux at 11 a.m.). Reduction of light intensity was obtained by covering growth cabinets with cheesecloth.
Additional artificial light was provided by HLRG 400W Phylips lamps. Near-isogenic lines of Tm-tomatoes were
used. Plants were inoculated at the 2-leaf stage with a 1:30 dilution of TMV infected plant sap in phosphate buffer.
The TMV isolates that were used in this test are reported in Table 1.
The percentage of diseased plants, the time interval between inoculation and symptom appearance, and the
type of symptoms were affected by light intensity (Table 2). Generally, light intensity hampered the induction of
disease symptoms by the three isolates of TMV on susceptible and on Tm-resistant tomatoes. The systemic
necrotic syndrome induced on Tm-2/+ and on Tm-2a/+ hosts by isolate C-217 at 7,000 lux tended to be substituted
partially at 14,000 lux and totally at 30,000 lux by systemic chlorotic spotting.
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