Development of Large Patch Resistant and Cold Hardy Zoysiagrass Cultivars for the Transition Zone.

Cold hardiness is the trait that limits the long-term survival of zoysiagrass in the transition zone. Furthermore, large patch disease caused by Rhizoctonia solani (AG 2-2 LP) has become the primary pest on zoysiagrass. Improved cultivars with good cold hardiness and large patch resistance are desired in the transition zone, which could reduce fungicide requirements and maintenance costs. TAES 5645, a Z. japonica genotype that exhibited resistance to large patch in preliminary studies, was used as a breeding parent and crossed with 22 cold hardy zoysiagrasses, resulting in 2,858 progeny. These progeny were evaluated for cold hardiness and agronomic traits. Sixty progeny were identified for further evaluation in larger plots and are being evaluated under golf course management conditions at 10 locations throughout the transition zone for turf quality characteristics and large patch resistance. In autumn 2016, the fungus causing large patch was inoculated in plots in Manhattan, KS and a natural infestation occurred in Stillwater, OK. Progeny showed a wide range of variability in turf quality characteristics including winter injury, spring green up, establishment rate, genetic color, leaf texture, turfgrass quality, and fall color. Several progeny had quality characteristics that were superior to Meyer zoysiagrass, the commonly used standard in the transition zone. In KS and OK in Nov. 2016, Meyer had 42 to 77% plot area affected by large patch; many of the progeny exhibited no symptoms. Among this group of experimental zoysiagrasses, there appear to be promising progeny that have good winter hardiness, resistance to large patch, and improved turf quality characteristics.