JWSS - Journal of Water and Soil Science

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This study was conducted at the Research Farm of Isfahan University of Technology in 2003 to evaluate drought tolerance potential of 20 oat (Avena sativa L.) genotypes including 14 cultivars released in Canada, two cultivars released in the United States of America and Switzerland and four Turkish breeding lines. A randomized complete block design with three replications was used in each irrigation treatment (i.e., irrigation after 70±3 and 130±3 mm evaporation from class A pan). Results of analysis of variance revealed significant differences among cultivars for all studied traits in both irrigation treatments, with the exception of plant height at heading stage and biological yield in stress condition. Stress condition significantly reduced all the traits. Also, the interaction of genotypes by irrigation treatments was significant for days to heading, grain and biological yields and 1000-grain weight. To evaluate drought tolerance of the studied cultivars, Rosielle and Hamblin tolerance index, mean productivity (MP), Fischer and Maurer stress susceptibility index and Fernandez geometric mean productivity and stress tolerance index were calculated based on yield data in stress and non- stress conditions. According to the obtained results, stress tolerance index seems to be the most effective index to identify tolerant genotypes. Rank correlations of stress tolerance index and grain yields in stress and non-stress conditions were 0.93 and 0.78, respectively. Based on this index, Boyer and Paisley were found to be the most tolerant cultivars.

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To study the effect of salt stress on quantitative and qualitative parameters of canola (Brassica napuse. L) cultivars, and determine the possible mechanisms of salt tolerance and the best salt tolerance indices, an experiment was conducted under a rain-shelter at experimental field of university of Kerman in 2004. The experimental design was a complete randomized block (RCOD) with four replications. Treatments consisted of all combinations of different levels of three factors including variety (Kobra×Regent, Ceres and Okapi), salt types (NaCl and CaCl₂) and electrical conductivity of saline solution (0, 4, 8 and 12 dS/m). All treatments were randomly distributed in each replication. Results of the analysis of variance showed that grain yield, yield components, oil and protein contents were significantly affected by salinity (P< 0.001). All the mentioned traits reduced with increasing salinity. It was also found that there were significant differences among genotypes for the mentioned traits. Cultivar of Kobra×Regent showed the highest values of the above traits except for the oil content. Proline, protein and sugar contents were also affected significantly by salinity (P<0.001). The highest and lowest sugar concentrations and protein contents were recorded for control and 12dS/m treatments, respectively. Proline content showed a reverse response and increased with increasing salinity. Mean productivity (MP), geometric mean productivity (GMP) and stress tolerance index (STI) are suggested to be the most suitable indices in order to select genotypes of high productivity under both stress and normal conditions. Based on these results, Kobra*Regent was selected as the most tolerant cultivar.

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In order to study the genetic diversity of 75 Iranian rice genotypes (45 Iranian land race, 25 improved cultivars, and 5 exotic cultivars) with respect to their salinity tolerance at seedling stage and to determine tolerance indices, based on biomass, genotypic code and Na⁺/K⁺ ratio a factorial experiment in randomized complete block design with three replications was conducted under control and salt stress(1.2, 4 and 8 dSm^-1) conditions at Rasht Rice Research Institute. Root and shoot length, root and shoot dry weight, Na⁺ and K⁺ concentrations, and genetic score were studied. Significant differences were detected among genotypes for all traits. Shoot length and K⁺ concentration had the highest and lowest heritability estimates, respectively. Genetic score under salinity stress showed that Tarom-mahalli, Gharib, Shahpasand Mazandaran and Ahlami-Tarom with more biological yield root and shoot lenghes, and low Na⁺/K⁺ ratio were tolerant. Khazar, Speedroud, IR28 and IR29 were the most sensitive cultivars. Tarommahalli, Ahlamitarom, Rashti and Chparsar had low tolerance index, mean productivity, stress sensitive index, geometric mean index, stress tolerance index and harmonic mean for genetic score, whereas Khazar and Speedroud had high values for theses indices. Cluster analysis, based on seedling traits at 4 and 8 dS.m^-1 divided the genotypes to three groups. Tolerante group had low genetic score and Na⁺/K⁺ ratio, but high root and shoot dry weight, biomass, root and shoot length.

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Chlorine and sulfate toxicity in water and soils are the main factors limiting growth and yield of most plants. Tolerance and sensitive indexes related to Cl and SO4 in irrigation water and effect of nitrogen fertilizer on barley were evaluated in a completely randomized design with three replications, under greenhouse conditions. Quantity salinity tolerance and susceptibility indices such as Mean Productivity (MP), Tolerance Index (TOL), Geometric Mean Productivity (GMP), Stress Susceptibility Index (SSI), Reduction Yield Ratio (Yr) and Stress Tolerance Index (STI) on the basis of plant yield with stress (Ys) and without stress (Yp) conditions were determined. Results showed that STI had a positive and highest significant correlation with grain and straw yields, compared to other indexes. Study of Standard Beta contents in grain and straw with STI index showed that the impact of Cl had a greater effect on reduction of salinity tolerance than SO4. Also Cl/SO4 ratios of 1:3 and 1:2 for grain and 1:2 and 1:1 for plant straw brought about highest tolerance to salinity, compared to non stress conditions. The scatter plot also confirmed such findings.