Physiological Response of Several Alfalfa Genotypes to Drought Stress

Alfalfa is generally considered resistant to drought, but its yield may fluctuate appreciably under drought conditions. The strategies for sustainable use of water and drought resistance improvement based on the physiological traits are important and physiological approaches should be integrated in conventional breeding. Research was performed on 74 alfalfa genotypes under vegetation house conditions at two watering levels. The objective was to identify the available genetic variation and to establish efficient testing methods for characters which might positively influence alfalfa performance under drought conditions. Our research focused on plant height, number of shoots, stomatal resistance and biomass yield. The results showed that for drought tolerant genotypes the plant height and number of shoots were reduced less than in sensitive ones. The stomatal resistance was higher for sensitive genotypes than for resistant ones, but there were some sensitive genotypes with low stomatal resistance and vice versa, which opens new opportunities to improve drought resistance. The results showed that the stomatal resistance of young plants was correlated with yield both under optimal conditions and stress conditions, indicating that stomatal resistance has a very significant impact on production both under stress and optimum conditions.