Mode of reproduction of colchicine-induced paspalum plicatulum tetraploids
Paspalum plicatulum Michx. is a wild forage grass species. The common races are tetraploid and apomictic, while sexual diploid representatives have been reported sporadically. Objectives of this study were to induce sexual 4x individuals from sexual diploids, determine the capacity for hybridization with other apomictic 4x species closely related with P. plicatulum, and thus create a tetraploid sexual material cross compatible with apomictic 4x species of the Plicatula group of Paspalum. Two induced tetraploid plants were recovered from germinating 2x seeds treated for 24 h with colchicine. Bivalent and quadrivalent chromosomes were the most common association at meiosis in these autotetraploids. Embryological analysis and progeny tests using molecular markers revealed that both induced tetraploids reproduced sexually. Single-seed screening by flow cytometry confirmed full sexual reproduction. These plants retained the high self-incompatibility system of the diploids, but set seed after reciprocal crosses and when crossed with pollen of apomictic 4x P. guenoarum Arechav. of the Plicatula group. Both sexual 4x plants constitute the foundational material for plant improvement through gene exchange and selection in apomictic 4x P. plicatulum and possibly in several apomictic species of the Plicatula group.