Towards understanding the genetic basis of adaptation to low rainfall environments.

Abstract

Water deficit is one of the most important constraints to cereal production in the Mediterranean-type dryland cropping environments of the world. The present project aims to identify and develop barley with improved adaptation to low rainfall environments, and to develop molecular markers for key traits associated with drought stress tolerance. While markers for these traits will find application within current breeding germplasm, this work also targets the identification of novel alleles from wild and landrace barley. A population was developed from a cross between a Syrian landrace barley and an improved ICARDA line. The two parental lines are well adapted to low rainfall conditions, exhibit similar maturity, and also represent significant genetic diversity. In 1999/2000, this population was evaluated at two low rainfall sites in Syria and four sites in Jordan. The sites experienced significant drought stress and a number of lines out-yielded the parental lines and well adapted local varieties, and the differences in yield were not associated with maturity effects. A range of traits associated with performance under drought stress were measured including growth habit, early vigor, tiller number, leaf chlorophyll content, plant height, days to heading, biomass, kernel weight, grain yield and harvest index. A molecular map has been constructed with 247 molecular markers (73 SSR, 174 AFLP) used to genotype 94 RIL’s from this population. Tolerance to drought stress has been a difficult trait to characterise and quantify, and our current understanding is largely based upon comparative physiology. The application of molecular genetics strategies in conjunction with physiology and field evaluation promises to deliver significant advances in both our understanding of stress tolerance, and our ability to positively select for stress tolerance in crop improvement.