Chromosome behaviour in the male and female sex mother cells of wheat(Triticum aestivumL.), oat (AvenasativaL.) and pearl millet(Pennisetum americanum(L.) Leeke)

Abstract

Abstract Chromosome behaviour in respect of chiasma distribution and frequency was studied in the pollen mother cells and embryosac mother cells of two populations each of wheat (Triticum aestivum) and oat (Avena sativa) and three populations of pearl millet (Pennisetum americanum). While regular bivalent formation was a normal feature in both the sex mother cells of oat with no variation observed in the chiasma frequency and distribution in male and female sex cells, in wheat one population showed regular bivalent formation in the two sex cells whereas the other population carried a reciprocal interchange involving two pairs of nonhomologous chromosomes in 80 and 71.42 per cent male and female sex cells, respectively. However, the presence of interchange did not effect the overall chiasma frequency which was almost similar in all the cells studied with or without a quadrivalent. In pearl millet, unlike oat and wheat, the chiasma frequency was higher in female sex cells than the male cells. Moreover, the distribution pattern of chiasmata varied drastically in the two sex cells at diakinesis and metaphase-I stages.It was predominantly terminal in male cells whereas in female cells interstitial chiasmata were mostly observed. It is concluded that in oat and wheat the contribution of the two sex cells towards generating variability through recombination are identical. In pearl millet it seems likely that the effective recombination is brought about chiefly by female meiotic bivalents and the male side provide for the retention of certain linkage groups. The importance of differential behaviour of chromosomes in the two sex cells is discussed.