Buffalograss is a warm-season (C4) grass species that originated in Central Mexico (Quinn and Engel, 1986; Quinn et al., 1994; Shaw et al., 1987; Webb, 1941). It is a fine-leaved, stoloniferous perennial grass species grown for turf in the Great Plains of North America (Shearman et al., 2004). Its inherent sod-forming characteristics (Wenger, 1949) makes it suitable for golf course, sports, home lawn, and utility turfs (Riordan et al., 1993). Buffalograss is a dioecious and self-incompatible species (Chase, 1979). Outcrossing is obligate and generates highly heterogeneous populations. Thus, buffalograss is highly variable with plants growing side by side differing in certain vegetative or reproductive characteristics (Wenger, 1949).
The genetic make-up of buffalograss is complex. It exists in several ploidy levels that are essentially alike phenotypically and indistinguishable from one another (Budak et al., 2004; Huff et al., 1993; Johnson et al., 2001; Reeder, 1971). The most prominent difference among ploidy levels is geographical adaptation (Shearman et al., 2004). The diploids are thought to be the original forms from which the upper ploidy levels evolved and are adapted to the southern regions of buffalograss-growing areas in North America. The tetraploids are southern and central-adapted, whereas the hexaploids are generally more widely adapted, but some, like ‘609’, are more suited to the southern range of buffalograss adaptation (Huff et al., 1993; Johnson et al., 2001). A molecular study of buffalograss genotypes of different ploidy levels observed a linear increase in the number of alleles in the hexaploids as compared with tetraploids and diploids (Budak et al., 2005). This increased number of alleles is believed to have contributed to the broad-based adaptation of the hexaploids.
Early buffalograss improvement efforts emphasized on selection and hybridization mostly to develop forage types (Wenger, 1949). Germplasm collections were found to have extensive variability from which increased vigor, green color retention, taller seed stalks, and increased disease-resistant types could be selected (Beetle, 1950). However, the level of improvement that can be achieved through hybridization is not well known. Recently, results from a buffalograss pseudo-testcross progeny study for improved seed production in Nebraska indicated that seed yield could be increased up to 10-fold by selective parental hybridization (Abeyo and Shearman, 2009). Organelle and nuclear analyses of buffalograsses with different ploidy series indicated that chloroplast and mitochondrial genomes are uniparental and variability was mainly the result of nuclear genome (Budak et al., 2005; Gulsen et al., 2005). Nevertheless, the potential amount of buffalograss improvement for turfgrass quality, pest resistance, and stress tolerance that may be achieved through hybridization has not been established.
It is essentially impossible to generate inbred buffalograss lines by self-fertilization because buffalograss is a self-incompatible, dioecious species (Brewbaker, 1957). Hence, the genotypes available for breeding are always heterozygous. The advantage of planned hybridization of heterozygous genotypes needs to be extensively studied for subsequent exploitation for the improvement of various traits in the breeding program.
This study was conducted to evaluate half-sib populations with the following objectives: 1) investigate the pattern of genetic variability generated for turfgrass characteristics through hybridization breeding; 2) assess if change in one parent has an effect on the level of genetic variability generated in a buffalograss diploid population; and 3) predict the performance of a progeny generated from two heterozygous parents for turfgrass performance.
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