Turfgrasses in the United States are classified as warm-season and cool-season species depending on the adaptation of each species to temperature. Warm-season grasses, originated from tropical regions, are best adapted to temperatures between 27 and 35 °C and primarily used in the southern United States. Two species, Bermudagrass [Cynodon dactylon var. dactylon (L.) Pers.] and St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze], dominate warm-season turfgrass production (Duble, 2013; Greene et al., 2008a). However, many cultivars of these two species require more intensive management to produce good-quality turf. Other warm-season grass species have been evaluated as alternatives with decreased management inputs (Duncan, 2000; Hanna, 1995; Hughes et al., 2002; Mancino, 1988; Riordan, 1991).
Common carpetgrass (Axonopus fissifolius Raddi) is a warm-season species native to Central America, South America, and the Caribbean (Bush, 1997). This grass was introduced into the United States through New Orleans during the early 1800s (Piper and Carrier, 1920). As a result of its low-maintenance requirements, common carpetgrass has been widely used as a pasture grass in Louisiana (Watson and Burson, 1985). It has also been naturalized in Texas, Mississippi, Alabama, Florida, Oklahoma, Arkansas, Georgia, South Carolina, and North Carolina (Hitchcock, 1950). Common carpetgrass can be used as an alternative low-maintenance lawn grass because it will persist and produce an acceptable turf surface with minimal amounts of applied nitrogen (Bush, 1997).
Common carpetgrass is a perennial, stoloniferous grass with folded vernation, a continuous collar, no auricle, and a hairy, short ligule fused at the base of the leaf. It has a boat-shaped leaf tip and flattened leaf sheath (Bruneau et al., 2008). The seed head of common carpetgrass usually includes two to three raceme-type branches with the upper two branches approximate and the third remote (Heath et al., 1985). Each spikelet on the raceme is ≈2 mm long and arranged in two alternating rows (Bogdan, 1977). Genetic variations of turf quality and morphological traits including some reproduction-related characteristics have been recently documented (Greene et al., 2008a, 2008b).
Common carpetgrass can be propagated both sexually and vegetatively (Heath et al., 1985). Although the turf can be easily established from sprigs, plugs, or sod, planting seed is a rapid and inexpensive method to establish a lawn because this grass germinates and establishes quickly (Bush, 1997). To produce adequate and high-quality seed of common carpetgrass, it is desirable to understand the inheritance of traits related to seed production.
Pollination type, which is the key factor for determination of appropriate methods to be used to improve a plant species in a breeding program, differs among different warm-season turfgrass species. Bermudagrass has a high degree of self-incompatibility with self-pollinated seed set ranging from 0.10% to 8.09% for different types of populations. The seed set for open pollination ranged from 2.8% to 57% among the populations (Kenna et al., 1983; Richardson et al., 1978). Seed set varies between diploid and tetraploid bahiagrass (Paspalum notatum Flüggé). Diploid bahiagrass was reported to have a 12% mean seed set for self-pollination and 39% for open pollination indicating moderate self-incompatibility. Sexual tetraploid bahiagrass had mean seed set of 21% and 27% for self- and open pollination, respectively, whereas artificially induced tetraploid had only 2% mean seed set for self-pollination and 14% for open pollination (Acuña et al., 2007). Seashore paspalum (Paspalum vaginatum Sw) is highly self-incompatible with a mean seed set of 0.02% for self-pollination and 7.7% to 66.3% for cross-pollination (Wang, 2012). Common carpetgrass can both self- and open-pollinate (Watson and Burson, 1985). However, there is no information comparing seed set between these two modes of pollination.
The objectives of this study were to compare seed set of common carpetgrass under self-pollination and open pollination and to estimate heritabilities of seed set, number of branches per inflorescence, and number of spikelets per branch.
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