Assessing the drought tolerance of Brachypodium ssp. genotypes by agronomic and physiologic indicators

Abiotic stresses including drought (both in terms of quantity and intensity) are serious threats to the sustainability of crop yields accounting for more crop productivity losses than any other factor in rainfed agriculture. Plant responses to water deficit can be analysed by systematically identifying traits that relate to drought tolerance followed by analysis to the cellular, biochemical and molecular levels. Brachypodium ssp, collected from Northern and central Tunisia, was considered as a potential genetic resource of drought resistance for poaceae and forage species. A group of 180 lines of the Tunisian Brachypodium ssp. representative of 9 populations were tested under three watering regimes: watering after two days, watering after four days and watering after six days. Twelve agronomic and physiologic traits were evaluated for their responses to drought stress on the basis of drought response index (DRI). Results show a considerable variation between genotypes and that the majority of traits showed medium (0.3 to 0.5) to high heritability (> 0.6) with low border value for total number of tiller and high border value for the ratio of productive tiller number per total number of tiller and an average value of 0.46. These findings are encouraging from the point of view of the potential for selecting for improved drought tolerance within that species. The method used allows detection after 3 months' growth of material that has the ability to grow at drought conditions which prevent the growth of other material, and the assumption is that they possess enhanced drought tolerance.