عنوان مقاله [English]
Drought is one of the most important stresses which reduce yields of crops and is one of the most important production constraints in arid and semi-arid regions. Iran with annual mean rainfall of 257 mm was classified among the arid regions of the world. Lentil is a pulse crop, rich in proteins and have 18 of the 20 amino acids including all 8 essential amino acids. Thus, lentils play an important role in human diet, especially in low-income people in the developing countries. In Iran, lentil is usually grown in rainfed areas. The average lentil yield in Iran is 476 and 1195 Kg.ha-1 in rainfed and irrigated farms, respectively. Identification of drought-tolerant genotypes is essential for cultivation in arid areas. To identify and select tolerant genotypes, researchers have proposed many drought indices based on a mathematical relationship between grain yield under stress and non-stress conditions, which are based on tolerance or susceptibility to drought genotypes. The aim of this study was to identify indicators that can identify high-yielding and drought tolerant genotypes in rainfed conditions of Mashhad.
Materials and Methods
This research was carried out at the Agricultural Research Station, Ferdowsi University of Mashhad, during growth season 2015. In this research, nine genotypes were used that eight genotypes of them were relatively drought tolerant in stress conditions and one genotype (MLC121) susceptible to drought stress were cultivated. These genotypes were selected from 73 genotypes including native populations and ICARDA genotypes in the seed bank of the Ferdowsi University of Mashhad, which were planted in the same plot at last year. Experiments were conducted as completely randomized design with non-stress and drought stress conditions (providing 100% and 40% water requirement of the plant) with three replications.
Results and Discussion
The analysis of variance showed a significant difference between yield genotypes in non-stress and drought stress conditions. Based on the results, in non-stress conditions, MLC356 and MLC121 genotypes produced the highest and lowest grain yields per hectare with 2621 and 993 kg.ha-1 respectively. Under stress conditions, Cabralinta and MLC121 genotypes produced the highest and lowest grain yields per hectare with 876 and 288 kg.ha-1, respectively. The mean yield of genotypes in non-stress and stress condition were 1616.7 and 625.6 kg.h-1, respectively that showed a decrease of 61.3% in water stress condition. Correlation between yields in stress and non-stress condition with tolerance indices showed that the old indices of STI, GMP, REI, HM and MP and the new K2STI index had a positive and significant correlation with yield in stress and non-stress conditions. The 3D Charts of the K2STI index with Yp and Ys showed that MLC356, Cabralinta and MLC025 genotypes had the highest rate of this index under non-stress and drought stress. The biplot drawing showed that high yielding genotypes are in D region. In this area, the old indices of YI, HM, GMP, REI, STI, the new indicators of SNPI K2STI and all of which are consistent with the Ys. The sharp angle between Ys, SNPI and YI indices shows a strong and positive correlation between these indices and indicates their superiority in separating high-tolerance genotypes with stress conditions and having relatively high performance in non-stress conditions. Considering this criterion, Cabralinta, MLC025, and MLC356 genotypes which had the highest correlation with the two indices, can be selected.
In all, the results of this study showed that SNPI and YI indices have a high correlation (99.9%) with performance in stress conditions, as well as K2STI, HM, GMP, REI and STI indices, all of which in D area. They have the most positive and significant correlations with each other and with performance in two conditions of non-stress and stress as the most suitable and effective criteria for identifying and selecting genotypes tolerant to drought stress. In all, if the goal is to introduce three genotypes, Cabralinta, MLC025 and, MLC356 genotypes which are the most susceptible genotypes are suggested compared to the stress conditions, but if the goal is to introduce only one genotype, Cabralinta genotype that has the highest and most stable yield under stress condition and in comparison with MLC356 genotype under stress conditions, 10.2% more yield could be introduced for arid and severe stress areas. For lentil planting in areas with mild stress, a high yielding genotype and tolerant, MLC356 genotype is recommended. It is also suggested that again to increase the accuracy of the experiment, three selected genotypes are again cultivated in the field.