On the basis of 5,591 gametes analyzed for yv
and Aps-1, the estimates of maximum map distance between
them is 0.00082 cM calculated at the 0.01 probability level, and the distance between (yv, Aps-1) and Mi, 0.00894
cM, based on 513 plants.
For practical breeding purposes, absence of recombination on the yv Aps-1 Mi region is welcome since in
the electrophoretic technique the selection is made for Aps-11 and consequently for Mi. The results obtained show
that unquestionably this procedure of screening for nematode resistance based on Aps-11 is remarkably reliable.
Although the possibility of a crossing over between Aps-11 and Mi is remote, a direct test with nematodes in the last
stages of the breeding programs would detect such an event.
Table. Estimates of recombination values of F2 and test cross populations of the cross yv Aps-1+/+ Mi+ coa c
a hl X + Aps-11/1 Mi ++++. Values calculated with pooled data of reciprocal FI's.
Oleszek, W., S. Shannon, and R. W. Robinson Glycoalkaloid composition of Solanum species of interest for
tomato breeding.
Glycoalkaloids have been of interest due to their possible role in insect and disease resistance, and have
also been of concern to potato breeders because of the toxic level of glycoalkaloids in a potato cultivar derived from
an interspecific cross with a wild Solanum species. The kinds and amounts of glycoalkaloids of Solanum species
that can be crossed with the tomato, however, have not been established yet.
Solanum pennellii, S. lycopersicoides and their hybrids with the tomato were compared to L. esculentum for
foliar glycoalkaloid composition. S. lycopersicoides, like the tomato and all other Lycopersicon species, has tomatine
as its sole glycoalkaloid constituent. The level of tomatine in the leaves of S. lycopersicoides, however, was 7 times
higher than in the tomato. The intergeneric hybrid was intermediate in tomatine content. S. pennellii also contained
tomatine, but at a much lower level than in the tomato. The low tomatine content of S. pennellii is a recessive trait.
Pilowsky, Vii. Studies on the reaction of Tm-2a/+ plants at high temperature.
In many tests when tomato lines heterozygous for the Tm-2a gene for resistance to tobacco mosaic virus
(TMV) were inoculated and grown at temperatures above 28oC, two types of symptoms, local reaction and systemic
necrosis, were observed. The present study was undertaken to test the possibility that the observed segregation in
the response of plants of genotype Tm-2a/+ to TMV at high temperature could be the result of genetic differences in
the parental material.
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