Cytogenetical Study of Induced Desynaptic Variants in <i>Phaseolus vulgaris</i> L.

Abstract

The cytological screening of gamma ray treated plants revealed few desynaptic plants where an enhanced frequency of univalents were found at metaphase I along with few bivalents. The desynaptic plants were obtained at 200 Gy dose of gamma rays and were characterised as weak and medium strong type. The univalents remained unpaired till later meiotic stages and resulted in the unequal separation of chromosomes at anaphase I. The unequal separation of chromosomes as a consequence of desynapsis lead to the formation of micronuclei and gametes with imbalanced chromosomes, thus affecting the post-meiotic stages also. The desynaptic plants possess very few pods and acquire high pollen inviability. The study suggests the ability of gamma rays in the creation of male sterile lines in Phaseolus vulgaris L. The gamma rays either act on the genes responsible for synapsis and chiasma formation or disrupt the synaptonemal complex affecting chiasmate dissociation. The desynaptic mutants could be used as a potential source for gathering information on chiasma maintenance mechanism as well as to study the genetic mechanism and consequences of male sterility in plants. Further, the male sterile lines could also be profitably utilized in hybridization breeding programmes to produce hybrid seeds.