Pachytene analysis in six species of Eu-Sorghum and their hybrid.

Critical analysis of chromosomes at pachytene and later stages of microsporogenesis in six different species of Eu-Sorghum namely S. vulgare, S. durra, S, caudatum, S. roxburghii, S. sudanense and S. virgatum and their 15 F1 hybrids were made. The hybrids involving one wild and one cultivated species showed relatively higher proportion of chromosomal abnormalities than those involving either both cultivated or both wild species. Pachytene pairing was found to be complete and apparently normal in two S. sudanense×S. durra and S. caudatum×S. roxburghii hybrids. Pachytene analysis in remaining 13 hybrids revealed the presence of some minute, though cytologically detectable, structural differences such as terminal as well as interstitial non-paired regions, small duplications and terminal deletions, and differential segments between the parental species. In spite of the existence of these meiotic irregularities in some hybrids, the subsequent stages of meiosis were quite normal leading to good seed setting. Cytogenetical mechanisms underlying species differentiation in the genus are discussed.