Evaluation of yield and salinity tolerance indices in wheat lines and cultivars under saline condition

Introduction
Salinity is one of the major environmental factors affecting the crop production of wheat (Triticum aestivum L.), specially, in arid and semi arid regions of the world. Remediation of saline soils and improvement of irrigation techniques are considered as alleviating methods in salt affected soils, but due to considerable costs, these methods are not feasible in every condition. Screening of varieties with tolerance to salt stress on the basis of yield, yield components and salinity tolerance indices is a suitable approach to deal with salinity and is important for future breeding programs (Houshmand et al. 2005; Poustini and Siosemardeh 2004; Saqib et al. 2005). Current study was carried done to evaluate different wheat lines and cultivars under saline condition of Zarindasht region; and to introduce a salt tolerant genotype for such circumstances.
 
Materials and methods
A field experiment was carried done to asses 14 wheat lines and cultivars under saline condition of Zarindasht region for two consecutive years. The experiment was in a completely randomized block design with four replications. Studied cultivars were: Chamran (as control), Sistan, Parsi, Haji Abad, Yavarous and Behrang. Also studied lines included of Line 34 and Line 73 which in companion with Sistan and Parsi cultivars were obtained from Yazd National Salinity Research Center. Lines 4 and 5 were the genotypes which had shown a considerable drought tolerance in experiments carried done in Fars Research Center for Agriculture and Natural Resources of Fars province. Other lines such as Ug 520, S-83-3, D-81-18, Line A were genotypes which had an optimum yield output in Darab region. The average soil and water salinity of the experiment location were about 6 and 9 dS m^-1 respectively. In both years of the experiment leaf samples were collected at earring stage and sent to laboratory for analysis. The concentration of sodium, potassium and chlorine were measured in the prepared samples. During growing season days to spick and days to maturity were recorded in different lines and cultivars. At the harvest time, plant height, grain yield and thousand seed weight were determined. All data were subjected to compound variance analysis and means were compared with Duncan’s multiple range test.
 
Results and discussion
Results indicated that the highest yield belonged to Ug 520 genotype in both years of the experiment (2660 and 3170 kg ha^-1 for first and second years of the experiment respectively). According to the obtained data for two year mean, Ug 520 showed 39 percent increase in yield production as compared to control. The evaluation of two-year yield means showed that after Ug 520, Line 5, Line 73, Line 4, Sistan, D-81-18, Line 34 and Parsi had greater grain yield than control (Chamra cultivar with 2095 kg ha^-1). As it was expected durum wheat lines and cultivars had higher thousand seed weight than other genotypes. Shortest and longest period to reach to spiking stage were belonged to Behrang and Ug 520 respectively. Similar results were achieved for days to maturity. In respect to leaf analysis results showed that the lowest potassium concentration was observed in Behrang, while the highest concentration occurred in Ug 520. Approximately a vice versa trend took place for leaf sodium concentration, so that, Ug 520 had the lowest sodium concentration and the highest concentration was observed in another durum wheat cultivar (Yavarous). Grain yield of lines and cultivars showed a negative correlation with sodium concentration in plant leaf, while this relation was positive for potassium concentration and potassium to sodium ratio.
 
Conclusion
Results of the present study indicated that early ripening lines and cultivars with the ability to take up higher concentrations of potassium or lower concentrations of sodium had higher potential to tolerate salinity stress and produce greater yield than susceptible ones. Among studied genotypes, Ug 520 with highest yield, earliest ripening, and optimum salinity tolerance indices was recognized as the best genotype to be planted in Darab and Zarindasht regions.
 
 Acknowledgments
The authors thank Yazd National Salinity Research Center for funding this project and providing the required seeds of wheat lines and cultivars.