Sex incidences of chiasmata variation in respect of position, distribution and frequency in some important legumes and grasses

Abstract

Abstract To find out whether the chromosomes behave in the similar fashion in two sex mother cells i.e. the pollen mother cells (PMCs) and the embryo sac mother cells (EMCs) in the bisexual plants, 13 species (19 accessions) of the families Fabaceae (7 spp; 12 acc.) and Poaceae (6 spp; 7acc.), were studied for male and female meiosis, ten (14acc.) being studied for the first time. The present study brought to light several facts not recorded earlier. Asynchrony was observed in the behaviour of chromosomes in the two sex cells with respect to the frequency, distribution and position of chiasmata. While a higher chiasmata frequency was recorded in the pollen mother cells (PMCs) of Lathyrus odoratus, L. sativus, L. aphaca, Lupinus albus and Pisum sativum, in species like Lolium perenne, L. multiflorum and Hordeum vulgare a reciprocal situation existed. Further, in L. perenne and L. multiflorum while bivalents showed distally localized chiasmata in the PMCs, in EMCs their distribution was random. However, in Vicia faba, Phaseolus vulgaris, Secale cereale, Lolium temulentum and Phalaris minor absence of a sex difference in meiosis was noted. Significant differences also existed in the bivalent size of the two sex cells in Lathyrus odoratus, L. sativus, V. faba and H. vulgare. In all these species, barring H. vulgare, the bivalent size was bigger in the PMCs studied. In H. vulgare a reverse situation existed. Sex difference in meiosis was distinctly evident in Lupinus albus. Of the two populations studied while one population showed synchronous behaviour of chromosomes in the two sex cells, the other population although showed normal microsporogenesis, its megasporogenesis was abnormal (desynaptic) being characterized by the failure of synapsed chromosomes to retain chiasmata in 61.11 per cent cells at diakinesis. It is concluded that the contribution of the two sex cells towards generating variability through recombination is not the same. In desynaptic L. albus while the effective recombination is brought about by the male meiosis, the female sex cells provide for the retention of certain linkage groups. The possible cause(s) and the significance of differential behaviour of chromosomes in the two sex mother cells of different species studied is discussed.