Zoysiagrass (Zoysia spp.) is a warm-season (C4) turfgrass that is popular in the transition zone of the United States (Dunn and Diesburg, 2004; Fry et al., 2008; Patton et al., 2007). Some desirable characteristics of zoysiagrasses include good density and resistance to pests (Fry and Huang, 2004). Zoysiagrass also requires less fertilizer and pesticides compared with some cool-season turfgrass species such as creeping bentgrass (Agrostis stolonifera L.) (Fry et al., 2008).
Large patch, caused by Rhizoctonia solani AG 2-2 LP, is the most common and severe disease of zoysiagrass in the transition zone and everywhere zoysiagrass is used. It can cause large areas of blighted turf in the spring and fall. Typical symptoms appear as light brown to straw-colored sunken patches with or without bright orange margins (Green et al., 1993; Smiley et al., 2005; Tisserat et al., 1994). Patches can range in size up to 6 m or more in diameter (Green et al., 1993; Tisserat et al., 1994) with healthy turfgrass sometimes scattered within the patches. During summer conditions, growth of new shoots from living stolons and rhizomes often results in full recovery.
Along with large patch, the relative lack of an acceptable level of winterhardiness and long period of winter dormancy are limiting factors in the widespread use of zoysiagrass cultivars in the transition zone. The level of winter injury varies widely among zoysiagrass genotypes (Patton and Reicher, 2007). ‘Meyer’ zoysiagrass (Z. japonica Steud.), a vegetatively propagated zoysiagrass cultivar, has been the most widely used cultivar on golf courses in the transition zone since 1952 (Fry et al., 2008). ‘Meyer’ and ‘Zenith’ zoysiagrass (Z. japonica), which is seed-propagated, have better freeze tolerance than cultivars such as ‘Zorro’, ‘Diamond’, and ‘Royal’, which are Z. matrella (Patton et al., 2007). However, ‘Meyer’ is slow to establish and recover, and it is coarser in texture than Z. matrella cultivars (Fry and Dernoeden, 1987; Patton and Reicher, 2007).
Since 2004, turfgrass researchers at Kansas State University have evaluated over 600 new zoysiagrass progeny for winter survival and quality (Okeyo et al., 2011; Zhang and Fry, 2006). These progeny were the result of genotypic crosses made at Texas A&M–Dallas, most of which involved one parent from Z. japonica and one from either a Z. matrella cultivar or ‘Emerald’ (Z. japonica × Z. pacifica). The crosses were made in an effort to develop one or more cultivars with freezing tolerance equivalent to or better than ‘Meyer’ as well as having good density, fine leaf texture, and quality. In a recent study, Okeyo et al. (2011) determined that several zoysiagrass progeny associated with reciprocal crosses of Z. matrella (L.) Merr. × Z. japonica or ‘Emerald’ × ‘Meyer’ demonstrated freezing tolerance comparable with ‘Meyer’. Furthermore, some also were superior to ‘Meyer’ in fall green color retention but not spring green color onset (Okeyo et al., 2011). In another study, Fry and Cloyd (2011) assessed the susceptibility of a select 14 of the zoysiagrass progeny and ‘Meyer’ to bluegrass billbug larval damage. The study found that lines 5313-71, DALZ 0102, 5321-18, and 5334-59 suffered significantly lower larval damage compared with ‘Meyer’ during the 2 years of the study.
The objective of this study was to evaluate the susceptibility to large patch of 14 new freeze-tolerant zoysiagrass progeny and ‘Meyer’ under growth chamber and field conditions. The 14 progeny are a subset of selections made from evaluations of the original 600 zoysiagrass progeny for cold tolerance and the other traits listed at Kansas State University.
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