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.

A promising way of addressing the issue of growing water scarcity is through wider use of drip irrigation, which delivers water and fertilizer to crops in a slow, targeted manner, and has been shown to increase yields and water use efficiency. Yet, drip irrigation system adoption is low, primarily due to the high capital cost of the pressurized piping network and the pump, and operating energy cost. Lowering the water pressure needed for drip emitters to deliver water can reduce both capital and operating costs of drip systems. Here we present the results from field trials of new pressure-compensating online drip emitters that operate with a minimum compensating inlet pressure of 15 kPa (0.15 bar), in comparison to typical commercial emitters with minimum pressures of 50–100 kPa (0.5–1.0 bar). The field trials were carried out on nine farms in Morocco and Jordan over the course of one irrigation season with freshwater and treated wastewater. Low-pressure emitters are shown to reduce hydraulic energy per unit volume of water delivered by 43% on average compared to commercial emitters, without significantly sacrificing water emission uniformity (low-pressure emitters show uniformities of 81–91%, compared to 87–96% for commercial emitters). This energy reduction could lead to savings of 22–31% in the capital cost of a pump and emitters and the energy cost for a typical drip irrigation system. Thus, the low-pressure online emitters can be used as substitutes to commercial emitters that require higher water pressures, leading to reduced environmental impact and lower system costs.

Biological nitrogen fixation has positive effects in the enhancement of soil nutrition and plants growth, especially under difficult conditions. The study assesses the effect of drought (40% field capacity) on growth, physiological and biochemical parameters of six symbioses involving two Moroccan alfalfa populations Adis-Tata (Ad) and Riche (Rc) and Moapa (Mo) variety and ArfRh2 (Rh2) and AufRh8 (Rh8) rhizobia isolated from Arfoud and Aufous, respectively. Results showed that drought decreased plants growth and nodulation. Physiologically, as response to stress, the nodules membrane stability was negatively affected. Biochemically, activities of peroxidase (POX), catalase (CAT), superoxide dismutase (SOD) and acid phosphatase (APase) increased in leaves and nodules. Ad-Rh2, Rc-Rh2 and Ad-Rh8 have been qualified as more drought tolerant. They showed high antioxidant activities and as consequence less membrane damages especially in their nodules. The increase in nodules health and antioxidant defense could results in the enhancement of plant drought tolerance under stress.

In arid and semi-arid climates characterized by low rainfall with a great annual and inter-annual irregularity, drought can occur at any time inducing large losses in crop yield. Leaf rolling is one of the adaptive morphological responses to the water deficit observed in a number of species including cereals. It reduces the leaf area exposed to sunlight and transpiration. The aim of the present work was to characterize the agronomical impact of water stress on a set of 16 Moroccan durum wheat varieties and to examine the possible correlations between leaf rolling and agronomic performances of these varieties. Experiments were conducted during three cropping seasons on a soil with a clay-loam texture at Tamellalet, in Marrakech region. The water stress was applied for one week to the studied varieties at tillering, and the degree of leaf rolling was determined at the end of the stress period. Strong differences between the varieties in the degree of leaf rolling upon water stress and in the ability to counteract drought were observed. Varieties displaying high leaf rolling showed less reduction in the yield components (number of ears per plant, number of grains per ear and weight of grains). The strong correlation observed between the degree of leaf rolling and maintaining of agronomic performance suggests that leaf rolling can be a criterion for water stress tolerance in durum wheat. This trait could thus be used as a morphological marker of tolerance to water stress. Key words: Durum wheat, water stress, leaf rolling, agronomic traits, grain yield, drought tolerance, Morocco.