Integrating statistical and ecophysiological analyses of genotype by environment interaction for grain filling of barley II. Grain growth

In Mediterranean areas, grain growth of temperate cereals often progresses under the harmful influence of drought and high temperature. Genotypic resp onses are mediated by the specific occurrence of these constraints, thus ca using genotype by environment (G x E) interaction. Field experiments were c arried out in 12 environments of northern Spain to characterize G x E on gr ain growth of five six-rowed and five two-rowed barley (Hordeum vulgare L.) cultivars. Grain growth was defined as the result of two components: grain -filling rate (GFR) and grain-filling duration (GFD). Genotypic and environ mental descriptors were used as concomitant variables at the levels of the genotypic and environmental factor to partition G x E. For a first explorat ion of G x E, AMMI (additive main effects and multiplicative interaction) m odels were used. Subsequently, separate factorial regression models were fi tted for GFR and GFD. G x E for GFR could be partially attributed to the jo int effect of two pre-anthesis climatic variables (rainfall during heading, and average maximum temperature during jointing). The factorial regression model for GFR explained more than half of the analysis of variance G x E s um of squares with a quarter of its degrees of freedom (d.f.). Overall, six -rowed cultivars were more affected by low rainfall at heading and high tem perature during jointing than two-rowed types. The inclusion of these pre-a nthesis variables suggests that G x E for GFR could be related to large dif ferences in source/sink balance between two- and six-rowed genotypes at ant hesis. The factorial regression model for GFD contained the pre-anthesis cl imatic covariable ratio of rainfall to total evapotranspirative demand duri ng heading, and the genotypic covariable anthesis date, suggesting that G x E for GFD was related to differences in phenology among genotypes. This mo del retained about 35% of the analysis of variance G x E sum of squares wit h fifth of its d.f. The success of the integration of statistical and ecoph ysiological tools for the explanation of grain filling in barley is discuss ed. (C) 1999 Elsevier Science B.V. All rights reserved.