Abstract
The detailed morphology of the pachytene chromosomes and microsporogenesis have been studied in the six Eu-Sorghums. The pachytene chromosomes are depicted on the basis of total length, relative length, arm ratio, amount and distribution of heterochromatin and number and position of chromomeres. The characteristics of each of the ten pachytene bivalents in the haploid complement are described in detail bringing out similarities and differences amongst them. Based on the idiograms of the pachytene chromosomes, the possible role of chromosomes in speciation and the relationship amongst these Eu-Sorghums are discussed. Two basic archetypes in the 20-chromosomed taxa have been suggested-one with five long chromosomes and the other with five short chromosomes. It is proposed that the present day cultivated forms of Eu-Sorghums are allopolyploids of crosses between two such forms.
