Pre-fertilization incompatibility barriers to interspecific hybridizations in Pennisetum species

Abstract

The study was undertaken at Punjab Agricultural University, Ludhiana, in 1991–1992 to investigate the behaviour of the pollen tubes of four wild Pennisetum species in the stigmatic tract of P. typhoides and to identify stages of pre-fertilization impediments to interspecific hybridization. Pollen germination was normal in crosses with P. violaceum, P. squamulatum and P. orientale and slightly inhibited in a cross with P. setaceum. Fertilization was accomplished within 3 h of pollination in a control cross within P. typhoides. P. typhoides × P. violaceum was a compatible cross and the pollen tubes of P. violaceum reached the ovary within 4 h of pollination. The presence of P. squamulatum and P. orientale pollen tubes in the ovary 10–15 h after pollination indicated the possibility of normal fertilization, while in crosses with P. setaceum, pollen tubes did not penetrate the ovary even 15 h after pollination. The study indicated that there is no impediment at the pollen germination stage or in the stigmatic hairy region. Delayed/restricted growth of pollen tubes indicated that the barrier operates in the styllar hairless region for the crosses with P. squamulatum and P. orientale, and at the ovarian level for the P. typhoides × P. setaceum cross.