Monaco, L.
Seedlings heterosygous for groups of marker genes were treated with colchicine. During various stages of growth thereafter, diploid shoots were pruned, leaving only tetraploid shoots as ascertained by pollen examination and gross morphological appearance. Although some seeds were produced by spontaneous fruiting in the field, it was advantageous to artificially self flowers on the tetraploid branches. Seeds were harvested separately for each branch, and the characters were scored in subsequent seedling segregations. The progenies were, consequently, F2 from duplex heterozygotes.
Most of the mutants tested could be classified with surprising reliability. Difficulties were encountered with al, and the results with rv must be interpreted in the light of the consistent deficiency of that homozygote observed in discaic segregations. Within the limits of the growth stages observed, dominance appeared complete for all gens doses for all mutants except c, H and La. Some individuals of +ccc seemed to be dist@shable, but certainly not all of this genotype could be identifid reliably. The dosage responses of H and La were not unexpected. But unexpected was the success in identifying all five genotypes in the H segregations. As shown in the second table, the H segregations are fit much better by chromatid segregation. The expected values for the two families in the following data are therefore calculated on the basis of chromatid segregation.
Genotype
____________________________________
Family ++++ +++H ++HH +HHH HHHH Chi-square
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1762
Expected 36 192 315 192 36
Observed 32 196 316 190 37 0.82
1765
Expected 41 221 379 221 41 2.700
Observed 35 230 394 209 38
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Greater difficulty was encountered in classifying the k segregants. The
family was too small to be very meaningful, but it was adequate to reveal that
short tapered hypocotyl without cotyledons is not likely a reliable index for
the LaLaLaLa genotype, because proportionally too many of them were counted.
Also, it did not seem possible to distinguish La+++ from ++++, both evidently
having the characteristics of the normal tomato leaf. For reasons of these
difficulties and the small size of the family, the data are not presented in
the following table.
Observed Expected (Chromosome) Expected (Chromatid)
________ _____________________ ____________________
Marker + m + m Chi-square + a Chi-square
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a\1 210 9 213 6 1.541 209 10 0.105
al 738 14 730 21 3.003 716 35 13.216
au 881 22 878 25 0.370 861 42 9.989
bu 860 26 861 25 0.041 845 41 5.654
c 214 5 213 6 0.171 209 10 2.200
dl 212 7 213 6 0.171 209 10 0.943
dl 864 22 861 25 0.370 845 41 9.332
H 722 30 730 21 3.968 716 35 0.749
865 38 878 25 6.952 861 42 0.400
l\1 832 34 861 25 3.334 845 41 1.253
210 9 213 6 1.543 209 10 0.105
rv 722 30 730 21 3.968 716 35 0.749
sf 717 35 730 21 9.601 716 35 0.000
tf 881 22 878 25 0.370 861 42 9.989
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In spite of the small populations, a surprising amount of information is
revealed by these tests. For chromosome 8, the consistently closer approach
to chromatid segregation for l\1 as compared with dl and bu places the former
distal to the latter two--a result not inconsistent with the present linkage
pattern. The same conclusions appear warranted concerning proximal loci for
au and tf on chromosomes 1 and 7 respectively.