Evaluation of drought tolerance in Hamedani alfalfa (Medicago sativa.L) ecotypes by tolerance and sensitivity indices

One of the most important and widespread environmental stresses is drought which has made limitation in agricultural productions. Many researches were done about drought stress. Plant improvement for drought tolerance is very complicated and difficult due to unpredictable environmental conditions and variability of cultivars responses in different degrees of drought stress. Alfalfa production on regions by alternative interval drought conditions is very important because of its adaptability and having tolerant germplasm. Alfalfa with specific morphological characteristics and adaptability of these traits to environmental stress especially drought conditions caused high production potential in these regions. Main parts of cold and even temperate regions of Iran cultivated unimproved populations or local ecotypes of Hamedani alfalfa.
Material and In this study alfalfa ecotypes seeds were obtained from these regions. This study was done to evaluate drought tolerance in 11 Hamedani alfalfa ecotypes through tolerance indices in the growing season 2011-2012 using randomized complete block design with three replications in two separate farm experiments at Torogh Research Station. The first experiment was complete irrigation (non-water deficit) once in a week as usual. Second experiment was drought conditions by changing in irrigation interval and making water deficit in ecotypes through 10 and 14-day irrigation intervals alternatively among growing season. The tolerance indices STI, SSI, GMP and MP evaluated by using of alfalfa ecotypes’ dry matter in both stressed and non-stressed conditions. Ecotypes distribution was drown on three dimensional graph based on these indices.
The positive and significant correlation between dried forage yield and MP, GMP and STI indices in both stressed and non-stressed conditions showed that these mentioned indices were the best indices. Chaleshtar and Famenin alfalfa ecotypes had the most potential of dried forage yield in both stressed and non-stressed conditions and had the first and second STI ranking respectively. STI index in comparison with the other indices was the better estimator for genotypes yield in both YP and YS conditions because it can separate A type genotypes from the other types. STI results revealed that Ghahavand, Chaleshtar,Sedighan and Famenin ecotypes were the most tolerant and Gharghologh and Hamedani were the most sensitive ecotypes. A genotype with higher STI is an indicator for higher yield potential in both conditions. Famenin and Chaleshtar alfalfa ecotypes had the higher MP with 8.8 and 8.7 and Gharghologh had the lower with 7.6. High TOL was an indicator for ecotype stress sensitivity and lower TOL lead to select the drought stress tolerate genotypes. Ordobad ecotype with 3.5 and Malek kandi with 0.9 TOL had the least and most index tolerance respectively.SSI indices Ordobad and Malek kandi caused the most drought sensitive and drought tolerate genotypes respectively. The results showed that between the studied genotypes, Ordobad with 1.9 SSI and Malek kandi with 0.5 SSI were the the most sensitive and tolerate genotypes respectively. Although Malek kandi with low SSI is relatively drought tolerate ecotype but its low yield prevent to select this ecotype. Chaleshtar and Famenin alfalfa ecotypes had the greatest dry matter yield potential in both condition and were the most tolerant ecotypes in this study. Classification of ecotypes in both stressed and non-stressed conditions showed that they allocated in four separated groups depending on yield in normal and stress environmental conditions.