Morphology, cytology and forage potential of Pennisetum americanum (L.) K. Schum. x P. Purpureum Schum. amphidiploids

Summary

F₁ hybrids between short-day photoperiod- sensitive ‘maiwa’ bulrush millet, Pennisetum americanum (2n=14), and elephant grass, P. purpureum (2n=28), are triploid (2n=21), sterile, and can only be propagated vegetatively. Fertile amphidiploids, (2n=42, with 21 bivalents) were produced by colchicine treatment. Good seed set was obtained upon selfing the amphidiploids and the progeny exhibited variable pollen fertility and bivalent univalent and multivalent formation.

Reciprocal crosses between elephant grass and the colchicine-induced amphidiploid failed to produce seeds. The ‘maiwa’ millet x amphidiploid cross resulted in poor seed set and the reciprocal failed. ‘Maiwa’ x amphidiploid hybrids were pollen sterile with 2n=21, rather than the expected 2n=28, indicating chromosome elimination.

Morphologically, the amphidiploids and ‘maiwa’ x amphidiploid hybrids closely resembled elephant grass and the F₁ hybrid. The amphidiploids showed no superiority over the F₁ hybrid and elephant grass in either forage yield or quality but one ‘maiwa’ x amphidiploid genotype surpassed a promising local elephant grass selection in forage dry matter yield and flowered for a relatively short period.