Native grass species, when used as low-input turf, offer many benefits that could address concerns about water use, sustainability, and increased turf management operating expenses (Diesburg et al., 1997). Low-maintenance turf often has lower visual and performance expectations than highly managed areas, and lower quality may be acceptable to the turf manager (Johnson, 2003). Hanks et al. (2005) suggested that acceptable turf quality is defined by color, leaf texture, density, and aesthetic appeal for the particular area in which it is grown. Low-input turf areas can include home lawns, roadsides, cemeteries, military installations, low-use parks and schools, or golf course roughs (Dernoeden et al., 1994; Hanks et al., 2005). The low-input turf area must provide a uniform appearance, compete with unwanted species, and stabilize the soil (Dernoeden et al., 1994; Diesburg et al., 1997).
Plant breeders have been evaluating and developing native and introduced grasses for use as low-input turf. The traditional turfgrasses are better adapted to high-input areas, whereas native grasses may perform better under lower traffic and at higher mowing heights (Johnson, 2008). Native grasses that have evolved under local conditions in North America are logical candidates for low-maintenance turf (Mintenko and Smith, 1999; Mintenko et al., 2002). Native species should be exploited in breeding programs for their adaptation to a broad range of soil and climate conditions (Willms et al., 2005) and their ability to withstand heat and drought stress with less irrigation (Johnson, 2000). Major obstacles in developing native grasses for turf include a poor tolerance to mowing, low seed production, and extended summer dormancy. Native accessions being developed as turf cultivars must also demonstrate limited growth, fine-textured leaves, and quick recovery from damage caused by traffic and wear (Romani et al., 2002).
The native species buffalograss [Buchloë dactyloides (Nutt.) Engelm.] has been extensively studied and developed for use as a low-input turf. Its benefits include tolerance to mowing and a vigorous, stoloniferous growth habit, which allows for a dense, uniform turf (Johnson, 2008). However, it requires more mowing than other species in both optimal and low-input treatments (Brede, 2002). Another potential limitation for this species is that as a warm-season grass, buffalograss may be dormant during cool temperatures, which can limit its use in the northern United States (Johnson, 2003). Meyer and Pedersen (1999) evaluated buffalograss and blue grama [Bouteloua gracilis ‘Alma’ (Willd. Ex Kunth) Lag. ex Griffiths], another warm-season native species, as low-input alternatives and found that neither provided acceptable cover, color, or quality in Minnesota. Other native grasses that have been evaluated for use as low-input turf include prairie junegrass (Watkins and Clark, 2009), sheep fescue (Festuca ovina L.) (McKernan et al., 2001), and tufted hairgrass [Deschampsia caespitosa (L.) P. Beauv.] (Watkins and Meyer, 2005). Very few native turfgrass cultivars have been developed.
Prairie junegrass, a native, cool-season perennial bunchgrass, is found throughout the Northern Hemisphere and has several attributes that make it a useful low-input turfgrass. The species may, in the northern United States, provide earlier spring green-up and produce adequate turf stands earlier than buffalograss. Prairie junegrass exhibits drought tolerance (Milnes et al., 1998), has a flexible root system, which allows it to adapt to water availability (Mueller-Dombois and Sims, 1966), is adapted to sandy soil (Pammell et al., 1901–1904), and survives at extreme temperatures (Dixon, 2000). This species is also slow-growing (Dixon, 2000; Soovali and Bender, 2006), which could reduce mowing requirements. Prairie junegrass has been shown to have a very low seed set for self-pollination compared with cross-pollination (Smith, 1944).
The Estonian cultivar Ilo (Soovali and Bender, 2006) and two Dutch cultivars, Barleria and Barkoel, released by Barenbrug Holland B.V. (Oosterhout, The Netherlands) (Alderson and Sharp, 1994) are the only cultivars of Koeleria macrantha developed for use as turf and all were derived from European germplasm. ‘Barkoel’ was a top performer for turf quality compared with other native species in low-input turfgrass trials in Manitoba, Canada (Mintenko et al., 2002). In another low-input study, unimproved native prairie junegrass accessions displayed early spring green-up almost immediately after snow melt, sooner than many other species (Mintenko and Smith, 1999); this has also been observed in Minnesota (personal observation). Early spring green-up is highly desired in northern climates for improving the early-season aesthetic value and playability of warm-season turf surfaces. It is proposed that as a result of their local adaptation, North American prairie junegrass ecotypes can provide unique and beneficial traits to the University of Minnesota breeding program.
The diverse natural range of this species provides plant breeders with a broad genetic base from which to select important turfgrass quality traits. Significant variation has been shown among 48 globally diverse National Plant Germplasm System accessions of prairie junegrass on important seed production characteristics (Clark and Watkins, 2010a) and turf quality traits (Clark and Watkins, 2010b).
Quantifying the variation in North American germplasm will assist the breeder in choosing the appropriate characteristics, selection intensities, and mating designs to achieve top-performing cultivars. It is important to evaluate the presence of genetic variability in the base population before initiating a selection program, because limited variability will lead to less significant gains over time (Surprenant and Michaud, 1988). Understanding the phenotypic variation of morphological and agronomic traits within a breeding population is crucial to the plant breeder in determining the potential application of the material such as for turf (Wright et al., 1983).
Genetic variation and heritability estimates help predict the response to selection for desired traits (Dudley and Moll, 1969). Estimating heritability, which is the amount of phenotypic variation in a population resulting from genetic differences, is important in choosing appropriate traits for selection (Fehr, 1991). Selecting for characteristics with high broad-sense heritability will lead to faster and increased gains in the offspring than selecting for traits with low heritability (Browning et al., 1994). Highly heritable traits could be correlated with important or complex traits, and these interactions could be exploited by the plant breeder (Kenworthy et al., 2006).
The selection of material to advance in a breeding program can be based on the performance of the genotype per se as well as the performance of its relatives. Broad-sense heritabilities have been calculated for turfgrasses using replicated clones on both an individual plant basis as well as based on the performance of the clonal mean (Bokmeyer et al., 2009; Burton and DeVane, 1953).
In addition to evaluating individual genotypes, the performance of germplasm from specific collection sites should be examined to elicit if any pooled set has greater genetic potential than the other materials in the study; turfgrass breeders could then focus future collection efforts on the site that resulted in superior germplasm. Superior performance could be the result of a significant combining ability, a high mean performance of desired traits, sufficient variation within the population, or high heritability. The objectives of this study were to 1) identify superior performing genotypes of prairie junegrass; 2) estimate the genetic variation in native prairie junegrass collection sites; and 3) calculate broad-sense heritability estimates for important turfgrass quality traits.
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