Cytogenetics of Some Haploid and Aneuploid Derivatives ofTriticum Aestivum

Open Access
Publisher Website
Google Scholar
Abstract
Treatment of inflorescences of the wheat variety N.P. 809 just prior to the onset of meiosis gave rise to several haploids (2n = 21) in the progeny. When the inflorescences were given a subsequent dose of X-rays after the emergence of the ear, several twin seedlings and a triplet arose in the progeny. Meiosis was studied in the microsporocytes of three different haploid plants. At pachytene, a few bivalents revealed associations at specific knob like intercalary regions or at the distal ends. A maximum frequency of 5 bivalents was found in one haploid plant. Various types of secondary associations were found both among univalents and bivalents and the incidence of such associations was found to decrease with an increase in bivalent frequency. It is suggested from the behaviour of the satellited univalents that all such associations arise from attractions in specific regions of the chromosomes. Multivalent associations were observed during meiosis in the twin and triplet plants. Nearly 50% of all the chromosomes formed multivalent associations in the triplet. The highest association observed was a decavalent; octavalents were frequent. The progenies of the haploids, twins and triplet had variable chromosome numbers and plant and ear characteristics. A high degree of karotype re-patterening occurs in them. A greater incidence of cytological and morphological changes was observed in the progeny of the triplet in comparison with those of the haploids. Most morphological abnormalities in bread wheat can be correlated with whole chromosome or segmental aneuploidy.