Identification of QTL associated with cold acclimation and freezing tolerance in Zoysia japonica

Authors: BROWN, JESSICA - North Carolina State University; YU, XINGWANG - North Carolina State University; HOLLOWAY, MCCAMY - North Carolina State University; Tuong, Tan; SCHWARTZ, BRIAN - University Of Georgia; PATTON, AARON - Purdue University; ARELANO, CONSUELO - North Carolina State University; Livingston, David; MILLA-LEWIS, SUSANA - North Carolina State University

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/2021
Publication Date: 1/25/2021
Citation: Brown, J., Yu, X., Holloway, M., Tuong, T.D., Schwartz, B., Patton, A., Arelano, C., Livingston, D.P., Milla-Lewis, S. 2021. Identification of QTL associated with cold acclimation and freezing tolerance in Zoysia japonica. Crop Science. https://doi.org/10.1002/csc2.20368.
DOI: https://doi.org/10.1002/csc2.20368

Interpretive Summary: Zoysiagrass is a popular warm-season turfgrass that is susceptible to freezing damage during winter. This is a study to better understand genetic controls of Zoysiagrass so that breeders can better select freezing tolerant germplasm. A quantitative trait loci (QTL) analysis was conducted with a cross between a relatively hardy and a non hardy genotype. Eleven regions of interest were found that directly related to freezing tolerance. Another analysis showed that these regions were related to abiotic stress genes such as cell wall changes and signal proteins that help the plant mitigate freezing conditions. These QTL are easy to identify and allow breeders to select freezing tolerant genotypes without having to grow the plant to maturity and test their winter hardiness in the field, which will allow breeders to develop new freezing tolerant cultivars.

Technical Abstract: Zoysiagrasses (Zoysia spp.) are relatively low-input and warm-season turfgrasses which have grown in popularity in the United States since their introduction in the 1890’s. Over thirty improved zoysiagrass cultivars were released in the past three decades, but many lack freezing tolerance and their use is limited to warm-humid climates. Understanding the genetic controls of winter hardiness and freezing tolerance in zoysiagrass could considerably benefit the breeding efforts to increase tolerance to freezing stress. In the present study, controlled environment acclimation and freezing tests were utilized to evaluate a Meyer x Victoria zoysiagrass mapping population for post-freezing surviving green tissue (SGT) and regrowth (RG). Quantitative trait loci (QTL) mapping analysis identified nine QTL associated with SGT, eight QTL linked to RG, and 22 QTL common in both traits, accounting for between 6.4 and 12.2% of the phenotypic variation. Eleven regions of interest overlapped with putative winter injury QTL identified in a previous field study. Upon sequence analysis, homologs of several abiotic response genes were found underlying these overlapping QTL regions. The homologs of these gene encode transcription factors, cell wall modification related proteins, and defense signal transduction related proteins. Following further validation, these QTL and their associated markers have potential to be utilized in future breeding efforts for the development of a broader pool of zoysiagrass cultivars capable of surviving in cold climates.