Mapping QTL for Digestibility Related Traits in Tall Fescue.

Tall fescue is an important cool season perennial forage in the United States. Digestibility of tall fescue is highly variable and a prominent determinant of animal productivity. Forage breeders have consistent effort on improving digestibility in tall fescue. The present study was conducted to construct linkage maps and identify QTL associated with digestibility in tall fescue. A pseudo F1 bi- parental population of 124 members was developed by crossing between HD28-56 (Š) and R43-64 (‰) genotypes. The population was phenotyped on maturity and in vitro dry matter digestibility (IVDMD) for consecutive three years using a replicated field experiment in Ardmore, Oklahoma following randomized complete block design. The genotyping of the population was done using SSRs and GBS- SNPs. GBS sequences and SSR scanning yielded 229,000 and 577 polymorphic SNPs and SSRs respectively. SNPs with very high missing values were disregarded, and thus 7000 SNPs (<20%) have been considered for linkage grouping. Linkage group construction and QTL mapping in the population using both the markers system together is underway, however linkage mapping using only SSR markers has been completed which will be used as reference map for finalizing the combined markers map. Joinmap 4.1 and R/ASMap is being used to construct the Linkage maps which will be followed by using R/qtl and QTL Cartographer V2.5 for QTL mapping.