GENOTYPE × ENVIRONMENT INTERACTIONS FOR IN VITRO DIGESTIBILITY OF TIMOTHY (Phleum pratense L.) GENOTYPES

Abstract

Improved in vitro digestibility (IVD) is an important goal in timothy (Phleum pratense L.) breeding. This study examines the effect of genotype × environment (GE) interactions on individual genotypes and examines two methods for identifying superior parental genotypes. Fifteen genotypes of similar maturity were grown in simulated swards (100 plants m−2) at five locations. IVD was determined at early heading. Highly significant effects were found for genotype, year, location and all their interactions. A regression stability analysis indicated that most genotypes responded in a predictable manner to environment. Genotypes which performed relatively well in all environments were identified. However, some useful genetic material, being "unstable", would be discarded using this approach. Genotypes with consistently high IVD were identified using a technique developed for grouping corn (Zea mays L.) hybrids. This approach is considered the more efficient for identifying superior parental genotypes. Although genotype (IVD should be based on performance in several environments, it is suggested that selection for IVD stability is important in developing narrow-based but not wide-based synthetics.Key words: Timothy, Phleum pratense L., genotype × environment interaction, in vitro digestibility, IVD