Genotype by environment interaction of barley (hordeum vulgare l.) in mediterranean environments

Resumen

The aim of this thesis was to understand the adaptation mechanisms of barley (Hordeum vulgare L.) in order to apply the knowledge to breeding and selection for improved yield in the Mediterranean basin. To achieve this, barley adaptation patterns brought about by breeding and selection over time in the Mediterranean basin was studied on several Mediterranean sites on an array of diverse genotypes from different breeding periods of breeding which included landraces, old and modern varieties from within and outside the Mediterranean basin. Most barley yield improvement seems to have been achieved on optimum conditions where modern varieties clearly out-yielded landraces and old varieties. There has not been much yield improvement on sites which experience severe drought stress where most often landraces out-yielded old and modern varieties. It appears that breeding has mostly favoured changes in marker allele frequencies closely linked to grain yield quantitative trait loci (QTLs) related to high yields under optimum environmental conditions. Selection has little favoured changes for adaptation to non-optimum conditions. This may serve to highlight difficulties in improving yield under stress environments or possible neglect of stress environments by breeding programs. Factorial regression models have showed that barley grain yield adaptation patterns (genotype by environment interaction) were driven by three key environmental variables namely potential evapotranspiration during source determination, minimum temperatures during sink determination and growing degree days during sink realisation. Key environmental variables driving adaptation patterns for grain weight (thousand grain weight-TGW), as determined by factorial regression models, were days with temperatures below 0ºC and evapotranspiration during sink realisation. Solar radiation during source determination and temperature differences during sink determination were the key environmental variables underlying adaptation patterns of barley grain number (grains-2) in the Mediterranean.