Alteration of Phenotypic Variances by the Endophyte of Tall Fescue

Abstract

Widespread infection of tall fescue (Festuca arundinacea Schreber) by the endophytic fungus (Acremonium coenophudum Morgan‐Jones and Gams) is responsible for poor performance of grazing animals. Because infection results in changes in phenotypic means for numerous traits, changes in phenotypic variances could also be a result of infection. Phenotypic variances for forage and seed production were investigated in studies of polycross families from endophyte‐infected (El) and endophyte‐free (EF) clones of 20 tall fescue genotypes. No significant phenotypic variance for forage production was detected among El families during the study. In 1989, phenotypic variances for EF were greater than El for both harvests, suggesting that the endophyte can mask plant genotypic variance. Significant phenotypic variances were observed for all seed production traits in both El and EF. Phenotypic variances for total seed weight and seed numbers in 1990 were greater for El than for EF. Estimates of genetic variance for these traits were not greater than twice the standard error in the EF state but were greater than twice the standard error in the El state. The resulting heritability estimates reflected this difference. Endophyte presence could result in overestimates of plant genotypic variance for these traits. Breeding strategies should consider presence or absence of endophyte and the possible effects on variances.