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POSTERS: Genetics of Resistance I

P-281 - Genetic Dissection of Rhizoctonia Large Patch Resistance in Zoysiagrass Through Biparental QTL Mapping

Monday, August 4, 2025
3:45 PM - 4:30 PM HST
Location: Exhibit Hall 3
Rhizoctonia large patch (RLP) threatens the aesthetic value and playability of warm-season turfgrasses. Although fungicides and cultural practices are widely used to control the disease, efforts to identify host genetic resistance remain largely untapped. This study aims to identify quantitative trait loci (QTL) linked to RLP resistance in zoysiagrass by analyzing 228 F1 progeny derived from Zoysia japonica acc. Meyer × Z. matrella acc. PI 231146. The progeny was grown in a randomized complete block design with two replications in Blairsville, GA. Plots were inoculated with Rhizoctonia solani AG 2-2LP isolate from GA in Spring and Fall 2023, followed by natural infections in 2024, and data on disease severity and turf quality were recorded. The female and male parent linkage maps contained 817 (1723 cM) and 639 SNPs (2039 cM), respectively, in 20 linkage groups. The male map identified 12 QTL on chromosomes 1, 2, 3, 5, 6, 7, 11, 14, and 19, including five major QTL explaining over 10% of the phenotypic variance (PV) and three detected across multiple traits and years. The female map revealed 12 QTL on chromosomes 1, 2, 3, 4, 5, 7, 12, 13, and 17, with seven major QTL explaining up to 14.5% PV and exhibiting stability across years and traits. Gene annotation identified genes involved in host resistance, including leucine-rich repeat, protein kinase, UDP-glycosyltransferase, and NB-ARC domain-containing proteins. This is the first field-based study identifying key loci for RLP resistance in zoysiagrass, with potential for marker-assisted breeding of resistant cultivars.