Marker assisted and phenotypic selection for digestibility in tall fescue

A. A. Hopkins, M.C. Saha, and F. Kirigwi

Improved digestibility is an important goal in tall fescue breeding. Our objective was to compare forage quality and yield of tall fescue genotypes selected using molecular markers, and the population from which they were selected.  More than 550 genotypes were screened for endophyte infection and presence of SSR markers associated with increased or decreased digestibility.  Twelve genotypes were selected based on presence of 3 positive and no negative digestibility markers; 9 genotypes were selected based on 2 or more negative and no positive digestibility markers.  All 432 genotypes were cloned and planted as an unreplicated nursery at one location and as a RCBD with two replications at a second location, both near Ardmore, OK.  Forage yield and digestibility data were collected in spring and fall, 2007.  Mean digestibility of positive marker selected genotypes was greater than that of negative marker selected plants in all environments; digestibility of non-marker plants was intermediate.  Average forage yield of positive marker plants was consistently below that of the population mean. Seed will be produced from populations divergently selected for digestibility based on markers only and phenotypic data only, and used to establish trials comparing gain from selection for the two methods.