Reproductive characterization of bahiagrass germplasm

Bahiagrass (Paspalum notatum Flugge) is one of the major forage grasses used for beef cattle production in the southern USA. Description of the reproductive characteristics of bahiagrass germplasm is needed for genetic improvement of this forage crop. The objective was to determine and compare the mode of reproduction of diploid and tetraploid germplasm of bahiagrass. Reproductive behavior was determined by embryo sac observations and a series of controlled pollination studies in the greenhouse and field in 2004 and 2005. Two sexual diploid populations ('Pensacola' and 'Tifton 9') were not different in self- or cross-fertility, indicating that the general fertility of the crop was not affected by phenotypic mass selection. Sexual diploids, as a group, were determined to be primarily cross-pollinated, with low but variable levels of self-fertility. A group of 20 artificially induced tetraploids was determined to be primarily sexual and cross-pollinated. Fertility of these autotetraploids was lower than the original diploids. Two selected sexual tetraploids produced similar amounts of seed when self- or cross-pollinated. In contrast, six other tetraploids, including the cultivars Argentine and Wilmington, the experimental hybrid Tifton 7, and three plant introductions 315732, 315733, and 315734 reproduced primarily by apomixis. The sexual or I apomictic expression, the general fertility, and other agronomic characteristics of these groups of tetraploids define their usefulness for genetic improvement research.