Mapping QTL for Traits Related to Summer Dormancy in Tall Fescue.

Tall fescue is an important perennial, cool season forage grass in the United States, and mediterranean morphotypes of the grass exhibits partial summer dormancy as drought adaptation. Summer dormancy is a phenomenon which is endogenously controlled and coupled with series of processes including growth reduction, cessation and /or senescence under extreme summer condition. Tall fescue breeders in the USA are focusing on using the trait for improved persistence of tall fescue during harsh summers. The present study was conducted to identify genomic region associated with summer dormancy related traits in tall fescue. In this study, a pseudo F1 bi- parental population of 195 members was developed by crossing between a Mediterranean parent, 103-2 and a Continental parent, R43-64. The population was genotyped using 2000 molecular markers consisting SSRs and DArT. Parent based linkages maps were produced using JOINMAP 4.0, and QTL mapping was conducted using QTL Cartographer V2.5. Total of 17 traits were used for QTL mapping in 22 linkage groups of each parent. More than 60 QTL were detected in 40 genomic regions.  Chromosome 1, 4, 5, 6, 7, 12, 13 and 21 in R43 and 3, 4, 9, 15, 18 and 20 in 103-2 parent were detected with major QTL for plant height, tiller number, new leaf, fresh biomass weight and dry biomass weight. The variability explained by these QTL ranged from 8-23. Markers in the flanking region of the identified QTL will be applied for marker assisted breeding in tall fescue for integration of summer dormancy in continental morphotypes.