Drought and heat responses in the wild wheat relative Aegilops geniculata Roth: Potential interest for wheat improvement

Wild wheat (Triticum aestivum L.) relatives could represent a valuable sour ce of genetic variation for improvement of abiotic stress tolerance in cult ivated wheat. A better knowledge of the adaptive strategies developed by th ese species is needed. A collection of 157 Aegilops geniculata accessions o riginating from different ecogeographical regions was studied during two su ccessive years for several traits related to water status, chlorophyll cont ent, and plant thermal regulation under Mediterranean field conditions. Clo se association was found between the studied traits and the origin of acces sions. Two adaptive strategies were distinguished. Accessions originating f rom harsh environments had low biomass, low grain production and high water -use efficiency (low C isotope discrimination). They were early, with small , thick leaves exhibiting low chlorophyll content, high surface temperature and low epidermal transpiration. We suggest that in these accessions, decr eased leaf chlorophyll content could limit the energy load from strong sunl ight. In accessions originating from regions with a mild Mediterranean clim ate, thermal regulation of the leaf may rather depend on transpiration, as suggested by high C isotope discrimination values. These accessions also we re characterized by high chlorophyll content, leaf area, and biomass produc tion. Associations between the physiological traits observed could help to better understand the relationship between abiotic stress tolerance and yie ld in cultivated wheats. Results obtained confirmed the potential value of Aegilops geniculata for improvement of high temperature and drought stress tolerance in wheat and could contribute to the choice of traits to be intro gressed and the accessions to be used in wide hybridization programs.