Quantitative Trait Loci (QTL) Analysis of Freezing Tolerance in Zoysiagrass.

Zoysiagrasses (Zoysia spp.) are warm-season turfgrasses well-adapted for use in the southern and transitional climatic zones of the United States.  Zoysiagrass is characterized by outstanding drought and heat tolerance. Combined with its low fertilization requirement, zoysiagrass has great potential as a low input turfgrass.  However, the use of Zoysia is often limited to warmer climates because of its relative lack of cold tolerance compared to cool-season grasses.  Limited progress has been made in the development of cold-tolerant zoysiagrass cultivars because of the complexity of the trait and a lack of efficient selection criteria.  Molecular markers associated with cold tolerance in zoysiagrass would be useful for effective selection of cold-tolerant lines before field testing. A zoysiagrass mapping population was developed from the cross of cold-tolerant ‘Meyer’ with cold-susceptible ‘Victoria’.  The 175 progeny of this cross and nine controls were planted in 2014 in three replications in a randomized complete block design (RCBD) in Laurel Springs, NC, and West Lafayette, IN based on the range of winter temperatures at these locations. Winter survival data was taken in spring 2015 with 59% survival in North Carolina and 21% in Indiana.  Simple sequence repeat markers (SSRs) and genotype-by-sequencing-derived single nucleotide polymorphism markers (SNPs) will be used to construct a linkage map.  The map will be used in conjunction with winter survival data to locate quantitative trait loci (QTL) associated with cold tolerance.  The identification of markers linked to genomic regions controlling cold tolerance in zoysiagrass would improve the accuracy and effectiveness of selection, which would ultimately lead to an increase in the availability of cold-tolerant cultivars.