Association of Simple Sequence Repeat (SSR) Markers with Submergence Response In Diverse Populations of Perennial Ryegrass.

Submergence stress can cause the death of turfgrass. Identification of the association between molecular markers and submergence tolerance-related traits facilitates an efficient selection of the tolerant cultivars for commercial production. A global collection of 99 diverse perennial ryegrass accessions was evaluated for submergence responses and analyzed with 109 simple sequence repeat (SSR) markers. Submergence significantly reduced leaf green color, chlorophyll fluorescence (Fv/Fm), maximum plant height (HT), and relative growth rate (GR). Significant variations in these trait values were observed among the accessions under submerged conditions. Rapid linkage-disequilibrium (LD) decay was identified within 4 cM. The analysis of population structure (Q) identified four subpopulations in the collection, but obvious relative kinship (K) was not found. The Q model was the best to describe associations between SSR and traits evaluated among several models tested, including the simple linear model, K, and Q + K models. Fifteen SSR markers were associated with a reduction in green color, Fv/Fm, HT, and RGR using the Q model and can be used for genetic improvement of submergence tolerance of perennial ryegrass after further validation. The diverse population of perennial ryegrass is a valuable resource for association mapping of stress tolerance-related physiological traits.