Sequential Reduction of Pennisetum squamulatum Genome Complement in P. glaucum (2n=28)*P. squamulatum (2n=56) Hybrids and their Progenies Revealed its Octoploid Status

P. squamulatum Fresen. is an important Pennisetum species by virtue of its characters, such as, apomixis, perenniality and stress tolerance, which can be utilized for pearl millet improvement. This species is hitherto believed to be 2n=6x=54, however, recent reports of 2n=56 cytotypes rendered to recheck the ploidy status. In present study, meiotic system of F1 and advanced hybrids, such as F2, F1 sibs, and BC1, involving P. squamulatum (2n=56) and P. glaucum (2x and 4x) were investigated following a scheme to sequentially reduce P. squamulatum chromosome complement to half, in order to determine its ploidy. The cytological results indicating high bivalent frequencies in these generations confirmed octoploid (instead of 6x) nature of P. squamulatum, alongwith its basic chromosome number as 7 (similar to pearl millet) with its allo-octoploid (or auto-allo octoploid) status. On the basis of cytogenetical studies viz. crossability, DNA content, genetic relatedness and cytology of advanced hybrids, placement of P. squamulatum in secondary gene pool of pearl millet is supported.