Document Type : Original Article
Authors
1 Soil and Water Research Department, Fars Agricultural and Natural Resources Research and Education Center, (AREEO), Shiraz, Iran
2 Seed and Plant Improvement Research Department, Fars Agricultural and Natural Resources Research and Education Center, AREEO, Shiraz, Iran
Abstract
Introduction
Environmental stresses are the most important factors reducing the yield of agricultural crops in the world. Salinity stress affects 20% of the worl’s arable lands, which increases day by day due to climate change and human activities. Wheat has great genetic diversity for salt tolerance. Improvement and development of salinity tolerant cultivars is a suitable solution to reduce the negative effects of salinity. This research was conducted to investigate and determine the most tolerant varieties and promising lines of wheat to different levels of irrigation water salinity.
Materials and methods
In order to evaluate the response of bread wheat cultivars and lines to different levels of salt water and to determine the salinity tolerance indices, a factorial greenhouse experiment was conducted in a completely randomized design with three replications in the Agricultural and Natural Resources Research and Education Center of Fars province in 1399-1400 years. The light condition of the greenhouse was natural and its temperature was in balance with the outside environment. The experimental factors included wheat genotypes and different degrees of salt water. Wheat genotypes including commercial cultivars and some promising lines including Sistan, Narin, Brat, Sarang, Shush, Ayeneh, Sahar, Mehrgan, Ms-90-15, Ms-92-8, Ms-93-5, Ms-93-6, Ms-93-14, Ms-93-16 and S-94-12 were investigated. The salinity treatments tested with salinities lower and higher than the tolerance limit of wheat in values of 1, 10 and 16 dS m-1. Grain yield (g pot-1) and yield components including 1000 grain weight, number of fertile spikes per pot, number of grains per spike and biological yield (g pot-1) were recorded. Also, using the grain yield data, stress tolerance indices were calculated for medium and severe salt stress. Also, selection index of ideal genotype (SIIG) technique was used in order to investigate genetic diversity and integrate different indices into one selection index. Data variance analysis for different traits was done using SAS statistical software version 9.1. and mean comparison was done using Duncan's multi-range test at 5% probability level.
Results and discussion
Medium salt stress caused a decrease of 30, 26, 24, 26 and 20% in grain yield, biological yield, number of spikes per pot, number of grains per spike and 1000 seed weight of genotypes compared to control respectively. These reductions for severe salt stress were 53, 50, 42, 43 and 33% respectively. Mean comparison for the average of all cultivars in salinity levels showed that Sarang, Mehrgan, Brat, Sistan, Narin and S-94-12, without significant differences, had the highest biological yield, respectively. Also, for other yield components, the same genotypes along with Shush had the highest amount without significant difference. For grain yield, Sarang, Mehrgan, S-94-12, Barat, Shush, Narin and Sistan genotypes had the highest values. In the medium saline environment, S-94-12 and MS-92-8 lines had the lowest and highest percentage of grain yield reduction, respectively, compared to the non-saline environment. For severe salinity environment, the same reductions were observed in Mehrgan variety and MS-93-6 line. Based on the obtained results, the use of saline water of 10 ds/m decreased the grain yield of Sistan, Narin, Ms-90-15, Ms-92-8, Ms-93-5, Ms-93-6, and Ms-93-14, Ms-93-16, Brat, Sarang, Shush, Ayeneh, Sahar, Mehrgan and S-94-12 by 32.6, 36.2, 24, 40.5, 29.8, 32.5, 32.3, 26, 27.3, 30.5, 36.6, 21.7, 26.8, 30.2 and 15.6% respectively compared to non-saline irrigation water. These reduction values for 16 dS m-1 were 47.3, 56.3, 47.8, 50.6, 57, 65.4, 56.2, 50.2, 51.2, 50.5, 50.6, 46.6, 50.8, 47.3, 43.4 and 48.8%. Sodium content of leaves increased significantly with increase in salinity stress. The lowest sodium content with the amount of 0.257 and 0.259 percent was observed in Mehrgan and Sarang. Leaf potassium content in Sistan, Mehrgan, Brat, Sarang and S-94-12 showed a significant increase compared to other genotypes. Mehrgan and Sarang cultivars had the lowest ion leakage with the amount of 33.04 and 34.44%, respectively. The highest ion leakage was observed MS-93-6, MS-93-14, MS-93-5 and MS-93-16 lines. In order to increase the selection efficiency of superior genotypes, in addition to stress tolerance indices, the selection index of ideal genotype (SIIG) was used to integrate all stress tolerance indices into a single index. Investigation of the relationships between genotypes using the biplot analysis method and salinity tolerance indices showed that MP, GMP, HM and STI indices had a positive and significant correlation with yield in all levels of salinity.
Conclusion
The results of the biplot analysis and the relatively high correlation between yield under normal and stress conditions showed that cultivars that have high yields under normal conditions will also show high yield under salinity stress conditions. Also, based on stress tolerance indices as well as SIIG selection index, Mehrgan, Sarang and Brat cultivars as well as promising line S-94-12 in greenhouse test conditions (under natural ambient light and temperature conditions), had better yield under saline conditions. The reason for this could be the greater adaptability of these cultivars to the climatic conditions of the introduced region compared to other investigated cultivars, including the cultivars introduced for saline conditions of other regions.
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