Molecular and phenotypic characterization of segregating progenies from crosses between sexual induced tetraploid and apomictic tetraploid genotypes of bahiagrass

WU H.; CARLOS A. ACUÑA; ANN R. BLOUNT; F. ALPETER; KENNETH H. QUESENBERRY

Buenos Aires, Argentina

Simposio; International Symposium on the Molecular Breeding of Forage and Turf; 2010

INTA

Bahiagrass, (Paspalum notatum Flugge), is a perennial warm-season grass recognized as one of the most important pasture and utility turf species of Florida and the southem Coastal Plain region of the United States. This diverse species contains germplasm with different ploidy levels and linked reproductive characteristics. Diploids (2n = 2x = 20) reproduce sexually while tetraploids (2n = 4x = 40) reproduce asexually by apomixis. Apomixis bypasses megasporogenesis and fertilization of the egg to result in asexual seed production following apospory and pseudogamy. Bahiagrass offers the opportunity for manipulating apomixis to generate highly productive hybrids that may result in new forage or turf cultivars. Apospory in tetraploid bahiagrass is believed to be inherited as a single dominant Mendelian factor with distorted segregation. This factor is located in a genomic region characterized by suppression of recombination. Synteny of molecular markers was detected between the apospory controlling region of bahiagrass and specific regions of rice (0ryzas sativa L .). A segregating progeny can be generated by making crosses between sexual induced tetraploid genotypes and apomictic tetraploid genotypes. We generated sexual tetraploid bahiagrass by treating tissue cultured calluses from the diploid cultivar Tifton 9 with colchicine. A segregating bahiagrass population was generated by hybridizing selected sexual and apomictic tetraploid genotypes. Our objective was to evaluate the variation in this type of progeny for traits of agronomic importante such as flowering pattern, rate of spread, and seasonal growth pattern, and to also determine the segregation ratio of apomicitic vs. sexual reproduction. We will present data evaluating mode of reproduction by comparative embryo sac and molecular marker analysis and present the observed variability for genetic improvement of growth habit and seasonal growth pattern. Total seasonal yield and distribution of yield of selected apomictic hybrid progeny will be compared to the tetraploid cultivar Argentine.