Assessment of summer drought tolerance variability in Mediterranean alfalfa (<i>Medicago sativa L</i>.) cultivars under Moroccan fields conditions

Abstract

Abstract This study was undertaken to assess levels of tolerance to summer drought in Medicago sativa genotypes and to comment on their abilities to adapt to Moroccan conditions. Sixteen alfalfa cultivars originating from the Mediterranean basin were tested at an experimental station in Morocco, located in the semi-arid bioclimatic area. Trials were conducted over three years and consisted of one continuously irrigated treatment and another irrigated treatment in which summer watering was withheld for 9 weeks. Results showed that summer water stress significantly reduced aboveground biomass in all of the cultivars tested. This reduction ranged between 23.9 and 42.6% compared with fully irrigated treatment. At the end of stress period, mean summer leaf senescence rate was 83.3%, with a significant difference between cultivars. Ground cover, estimated at the end of summer in the third year, decreased dramatically and ranged between 12 and 30.7%, depending on the cultivar. High intrinsic water-use efficiency was associated with a decrease in stomatal conductance rather than an increase in photosynthesis. Keywords: Medicago sativa summer droughtbiomasspersistenceIWUE Acknowledgements This study was funded by EU within the project PERMED (INCO-CT-2004-509140): ‘Improvement of native perennial forage plants for sustainability of Mediterranean farming systems’ We thank farmers who have made available their materials for this study. We are grateful to F. Lelièvre for project co-ordination and to P. Annicchiarico and L. Pecetti for their technical assistance.