Genetic Control of Glycinebetaine Level in Barley1

Abstract

The accumulation of betaine (glycinebetaine, N,N,N‐trimethylglycine) in water‐ or salt‐stressed barley (Hordeum vulgare L.) plants may be a metabolic adaptation to stress. We investigated the inheritance of betaine level using genotypes varying in betaine content. Shoots of unstressed plants grown in growth chambers were assayed for betaine at the three‐leaf stage. Analyses of four pairs of reciprocal crosses indicated that neither maternal nor cytoplasmic effects were significant but that there may be some dominance of the low betaine trait. An incomplete diallel made with eight low‐ and five high‐betaine parents indicated that general combining ability accounted for the majority (74.6%) of genetic effects, suggesting a largely additive trait. Additive, dominance, and epistatic components of heritability were estimated by generation mean analysis of the parental, F1, F2, and backcross generations of a single high‐ × low‐betaine cross. This analysis also showed that betaine accumulation was a predominantly additive trait. Narrow‐sense heritability values for the trait were 0.53 and 0.63 from midparent‐offspring regression and generation mean analysis, respectively. The level of betaine accumulation in barley is a nuclear, predominantly additive trait of relatively high narrow‐sense heritability. Therefore, evaluation of the adaptive significance of betaine in water and salt‐stressed plants should be possible using an isopopulation approach.