Evaluation of drought tolerance in endemic ecotypes of cumin using tolerance indices

Cumin is known as the most important cultivated medicinal plant in Iran that its importance and cultivation area increase every year. Cumin seed yield reduction occurs in most regions of Iran due to the water stress. So far, based on literature review, major evaluations have been done using limited cumin ecotypes or mainly conducted under normal irrigated condition in the country; So this study was designed to assess the most diverse cumin ecotypes currently cultivated in the major cumin cultivation areas of Iran in terms of seed yield, determination the effect of drought stress during flowering stage, identification of drought tolerant ecotypes to from segregating population using tolerance indices and indication of ecotypes response to drought stress and normal irrigation conditions.
To determine the effect of water stress on yield of 49 cumin ecotypes adapted to Iran, a simple 7 × 7 lattice design with two replications was conducted in research farm of college of Aburaihan, University of Tehran. Experiment was conducted during 2012-13 crop season. Water stress initiated at 50% flowering stage when the soil humidity reached to 30% field capacity. Analysis of variance based on lattice design and evaluation of the relative performance compared to randomized complete block design were done. Further analysis was done based on randomized block design after correction of data. Calculation of 11 drought tolerance indices based on yield under drought and normal irrigated conditions, correlations among indices and seed yield and principle component analysis based on correlation coefficient matric were followed.
Lattice design relative performance compared to randomized complete block design was 153 and 148 percent in normal and stress conditions, respectively. Eleven different tolerance indices were estimated based on yield in both conditions. Correlation analysis, principal component analysis and biplot display showed indices MP, GMP, STI, Harm, K1STI and K2STI as suitable indicators showing high yield potential and stability. Cluster analysis based on indices grouped all ecotypes into three distinct groups. Tolerant ecotypes were placed in the same group. Ecotypes distribution in the biplot revealed genetic variation among genotypes regarding drought tolerance response.
Ecotype of Kerman (Baft), South Khorasan (Darmian) and Yazd (Sadooq) identified as most tolerant ecotypes while ecotypes from North Khorasan (Esfaraien), Esfahan (Ardestan) and Khorasan-Razavi (Kashmar) identified as most sensitive ecotypes to drought stress in flowering stage. Then usage of these accessions are recommended as parents to improve tolerant cumin cultivars in breeding programs.