Generation and Characterization of a Sexual Tetraploid Genotype of Seashore Paspalum (Paspalum vaginatum) for Novel Breeding Strategies
Breeding Paspalum vaginatum has been limited to the diploid germplasm; however there is a rich diversity in closely related species that may be utilized. The species is diploid and outcrossing due to self-incompatibility. This research aimed to generate a chromosome-doubled tetraploid and evaluate the effects of chromosome doubling on phenotype and reproductive mode. Both seeds and seedlings from a diploid population were treated with 0.2% colchicine for either 24 or 48 h. Morphological, anatomical, and reproductive traits were evaluated in both cytotypes. Megasporogenesis and megagametogenesis were assessed using complementary histological and optical approaches, and seed set was evaluated under self- and open-pollination. A tetraploid genotype was successfully generated from seedlings treated with colchicine for 24 h with an efficiency of 0.2%. The size of tillers, leaves, inflorescences, stomata, and pollen grains increased in the tetraploid, which also exhibited darker green coloration and greater vigor. Embryo sac development was similar in both cytotypes, indicating that the induced tetraploid remained sexual. No seed set was observed under self-pollination, whereas limited seed set under open-pollination confirmed that the tetraploid is an outcrosser. This new tetraploid provides a valuable bridge parent for introgressing genetic variation from cross-compatible polyploid Paspalum species through interspecific hybridization and the manipulation of apomixis.