Wild and cultivated barley genotypes demonstrate varying ability to acclimate to plant water deficits

Abstract

Wild barley ( Hordeum spontaneum Koech.) crosses easily with cultivated barley ( Hordeum vulgare L.) and so can be used as novel germplasm in breeding programs. In order to examine the potential usefulness of wild barley as a source of germplasm with characteristics beneficial to crop plants exposed to plant water deficits, wild barley accessions were collected from a range of habitats in Israel. Photosynthesis capacity at low leaf water potential (Ψ w), and cellular-level stress acclimation capability were evaluated in these lines. Genotypes identified as having the capacity to maintain higher photosynthesis at low leaf Ψ w (i.e.‘high acclimation lines’), as a group, demonstrated several related cellular-level physiological acclimation mechanisms when exposed to water deficits. These genotypes underwent relatively greater osmotic adjustment under stress. Osmotic adjustment in these lines was associated with the capacity to shift the protoplast volume/leaf Ψ w relationship upon exposure to stress such that greater cell volume was maintained at low Ψ w. Wild barley accessions which showed low photosynthesis under stress did not demonstrate this acclimation mechanism. Some of the wild barley accessions demonstrated greater osmotic adjustment in response to plan water deficits than the two varieties of cultivated barley which were also evaluated in this study. It is concluded that wild barley may be a good source of germplasm which shows resistance to water stress, specifically regarding the capacity to acclimate to plant water deficits such that photosynthesis is not as sensitive to low leaf Ψ w.