Cytological studies on diploid and polyploid taxa of the genusPennisetumRich

摘要

The cytology of thirteen taxa and two hybrids in the genusPennisetumindicated the distribution of the taxa among the four basic chromosome numbers 5, 7, 8 and 9. The diploid nature ofP. ramosumandP. typhoidesand the genomic allotetraploid status ofP. purpureumwas further confirmed.P. massaicum(2n=32),P. orientale(2n=36) andP. subangustum(2n=36) suggested probable autotetraploid nature and the three hexaploids (2n=54) investigated (P. polystachyon, P. longistylisandP. squamulatum) revealed allohexaploid constitution. The natural triploid,P. ruppellii(2n=27) and pentaploidP. villosum(2n=45) were found to be apomicts and they were allotriploid and allopentaploid respectively. The tetraploid-hexaploid complex ofP. pedicellatumshowed them to be cytotypes only. The cytogenetical behaviour of the hybrid,P. typhoidesxP. purpureumwith 2n=21 and the trispecies hybrid (P. typhoidesxP. purpureum) xP. squamulatumwith 2n=48 brought out the homology within the genomes of x=7 and x=9 and also between the genomes with x=7 and x=9. The significance of the inter- and intragenomic chromosome pairing had been brought out from the interspecific hybrids and the natural allotriploid and allopentaploid species having one genome in the haploid condition.