In a diploid interspecific hybrid between L. esculentum v. Bigboy X L. pimpinellifolium (LA2345) defects in pachytene chromosome pairing in microsporocytes were observed reflecting the morphological differences between the two parental chromosomes. The present study not only brought out clearly the existence of cryptic structural differences between the chromosomes of the two species but also facilitated the identification of specific chromosomes or regions involved in such a differentiation. Regular bivalent formation was observed at diakinesis and metaphase I. There is no significant reduction in chiasma frequency and pollen fertility in the F1 hybrid.
Though chromosome pairing is normal in certain PMCs, defects in pairing were observed in euchromatic, heterochromatic and centric regions of other chromosomes. They are -- unpaired segments in chromosomes-2, 4, 7 and 11; foldback pairing in chromosome-9; hump formation in chromosome-2; loose pairing in chromosomes-2, 3, 5, 8 and 10; and differential chromomeric pattern in chromosome-1. These defects are not always found in all the PMCs. This may be due to masking of one chromosome by the other; or by stretching or contraction of one of the chromosomes in a bivalent to adjust in pairing. It is significant to note that other hybrids of the same combination involving a different set of accessions did not reveal any such defects in pairing as observed in this study (Rao, 1981; PhD Thesis, Andhra University, Waltair).