Crossover frequency in the balanced lethal: white-8896/luteus-10 for chromosome 6

Self seed from two stocks, one that was Y+/y w15-8896 and the other Y+/y l10, was obtained from Dr. Robertson. Both recessives are closely linked with the y locus. Crosses between the two stocks were made, using green plants from the yellow seeds. The white seeds from crosses that segregated yellow and white seeds were heterozygous for albino and luteus in a balanced makeup which produced green plants. These were crossed with a yellow endosperm stock, and the progeny were selfed. All segregated yellow vs white seeds: 155 segregated for albino, 158 segregated for luteus seedlings. In addition, there were two classes that came from crossing over between the two loci. There were 9 in one crossover class that lost both recessives and therefore had only green seedlings. The complementary class has both recessives. Plants homozygous for both recessives have the albino phenotype. Plants heterozygous for this crossover are recognizable only when a new crossover separates the two factors. There were 3 plants of this type. The seedling counts on these are:

Table.

Larger samples from the ears segregating white seedlings need to be grown to identify all plants of this crossover type. Using the 9 plus 3 identified crossovers, the recombination value is 3.7%.

Lindstrom (Genetics 10:442, 1925) reported that a plant homozygous for luteus-1 is green, but if homozygous also for w, w2 or w3 is yellow. The homozygote for luteus-2 is yellow, but the homozygote for both luteus-2 and w is white. I tested many combinations of different yellow and white seedlings in barley. In all cases, the combination of white with yellow was a white seedling.

Charles R. Burnham


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