Symbiont Regulation and Reducing Ergot Alkaloid Concentration by Breeding Endophyte-Infected Tall Fescue

Abstract

Ergot alkaloids in endophyte-infected (E+) tall fescue (Festuca arundinacea) are responsible for livestock toxicosis. The host plant is capable of modifying the extent to which endophyte produces ergot alkaloids, possibly via endophyte nutrition by the host. Endophytes vary in alkaloid production. Maintaining the E+ tall fescue is essential for plant survival. Therefore, crop scientists are interested in reducing alkaloid concentration of E+ tall fescue. The objectives of this study were to determine maternal and paternal effects as an estimate of plant and endophyte genotype interactions for ergot alkaloid phenotype and the heritability of the ergot alkaloid trait in divergently selected E+ tall fescue populations. Diallel crosses were conducted among four tall fescue genotypes that varied in alkaloid concentration. Five of six crosses had progeny means less than the parental means when genotypes with lowest alkaloid were the female parents. Four of six crosses had progeny means similar to the parental means of crosses when high alkaloid genotypes were the female parents. Large ranges in progeny suggest an interaction between endophyte and plant affects alkaloid phenotype. In a second experiment, a tall fescue population was screened for alkaloid concentration. Low- and high-alkaloid plants were selected and poly-crossed within each class. Mean alkaloid concentrations of the high- and low-alkaloid progeny were higher or lower than the parental population. The trait was highly heritable and alkaloid concentration was reduced by 86% in the low-alkaloid population after two generations of selection.