The mechanism regulating pairing in Triticum timopheevi 1)
Moshe FELDMAN
Curtis Hall, University of Missouri, Columbia, U. S. A.
UPADHYA and SWAMINATHN (Indian Jour. Genet. & Pl. Breed., 1965) studied the mechanism regulating pairing in T. zhukovskyi, a natural autoallohexaploid which arose presumably from the cross T. timopheevi x T. monococcum. In a comparative study of meiosis in the 41- and 42-chromosome hybrids between Chinese Spring Mono-5B and T. zhukovskyi, they found that the number of chromosomes entering into as sociations increased when 5B of Chinese Spring was absent. Thus, they concluded that a gene system similar to that found in chromosome 5B of T. aestivum var. vulgare might not be present in T. zhukovskyi, and, therefore, also not in T. timopheevi.
In the course of my work, 41- and 42-chromosome hybrids were obtained from the cross of Chinese Spring Mono-5B with the amphidiploid T. timopheevi -Ae. squarrosa. The 42-chromosome hybrid showed slightly more chromosomal pairing at metaphase I (see table). This is actually what is expected in disomic conditions as compared to monsomic. These mean pairing values indicate that T. timopheevi chromosome which correspond to 5B of Chinese compensates completely for the nullisomci condition of Chinese 5B. It appears, therefore, that T. timopheevi contains a gene system on this chromosome identical with that found in chromosome 5B of T. aestivum.
