Investigating drought resistance mechanisms and quantitative trait loci mapping in bermudagrass for stress resistance traits

Bermudagrass is a C4, perennial grass grown widely for turf, home lawns, and livestock feed. However, its cultivation is often challenged by stress caused by water shortages and low temperature during winter. Thus, this study aimed to understand the drought resistance mechanisms in bermudagrass and identify the genomic regions associated with drought stress, salt stress and winterkill in bermudagrass through two greenhouse study and one field study. In first greenhouse study, three hybrid bermudagrass cultivars (‘Tifway’, ‘TifTuf’, and ‘Tahoma 31’) and one experimental selection (TifB16117) were evaluated through a controlled dry-down study in lysimeters. Results indicated TifB16117 as a superior performing experimental line under drought, comparable to the industry drought standard TifTuf. Genotypes performing superior under drought had higher total dry root weight (RDW), highlighting the role of well-developed root systems in bermudagrass drought tolerance. Second study was conducted to identify the genetic mechanisms associated with salt tolerance using the first-generation selfed (S1) population (104 individuals) derived from African bermudagrass genotype ‘OKC 1163’ in controlled- environment conditions. Plants were sub-merged in salt solution and screened based on morphological traits: visual leaf firing (LF) and percent green cover (PGC). Altogether, fifteen QTL on linkage groups (LGs) 1, 2, 3, 4, 5, 6, and 7 were found associated with salt tolerance. Among these, four QTL, QCTST1, QCTST2, QCTST4, and QCTST6 were consistently reported across years under salt stress. Field study included a mapping population of 213 first generation self-pollinated progeny (S1) of common bermudagrass genotype ‘A12400’. Phenotypic data was collected through visual assessment for establishment rate (ER), spring green-up (SG), winterkill (WK), and leaf firing (LF) in 2024 and 2025. High-density linkage map consisting of 18 linkage groups and expanding 2198.64 cM was constructed using 3289 polymorphic high-quality SNPs. Altogether, four QTL for ER, three for WK, twelve for SG and ten for LF were identified. Consistent QTL were found for ER (QCD.ER.OSU.1B.36), SG (QCD.SG.OSU.6B.21), and LF (QCD.LF.OSU.3A.12 and QCD.LF.OSU.3A.14). Results from this study provided new information to understand the physiological and genetic mechanisms of adaptive and stress resistant traits in bermudagrass and could be used in the marker-assisted selection for bermudagrass breeding programs.