Response to Salinity of Three Early Ripening Rainfed Wheat Cultivars and Barzegar Local Check in Yazd Province of Central Iran

Scarce water resources and raising salinity are limiting factors affecting wheat production in arid and semi-arid regions. Many studies have been conducted to release appropriate wheat cultivars for saline and non-saline conditions. But due to the co-existence of drought and salinity stress in arid and semi-arid regions, it is necessary to introduce cultivars that could tolerate salt under water shortage conditions. Results of the studies conducted at the Iranian Dryland Agricultural Research Institute have led to introduction of wheat cultivars with low water requirements due to early maturity. So, if the yield of these cultivars be optimum in saline media, they could be a suitable option for planting in these conditions. The objective of the study was to evaluate the salinity response of three dryland wheat cultivars in water limitation conditions compared to the local check.

To investigate the response to salinity of three early ripening dryland wheat cultivars along with a commercial irrigated wheat variety cultivated in the region, a field experiment was carried out as split plot during the 2020-2021 cropping season in Yazd province, central Iran. Treatments were irrigation water salinity with two levels of 2.5 and 10 dS m-1 as main plots, and three dryland cultivars of Asman, Aftab, and Kohdasht along with the irrigated cultivar of Barzegar as sub plots. All examined cultivars were planted on November 15. Row spacing was 20 cm with a planting density of 500 kernels/m2. The plots were subjected to saline irrigation water for 7 times from seeding to physiological maturity, and the irrigation was cut-off when physiological maturity occurred in dryland cultivars. Total water consumed throughout the growing period was 7794.8 m3 ha-1. Leaf area index was measured by sampling at plant establishment, tillering, mid-stem elongation, spike emergence, and kernel milky and dough stages. At harvesting, total above-ground dry mass and grain yield, harvest index, plant height and thousand kernel weight were measured. The grain quality attributes including hectoliter weight, protein content, zeleny sedimentation volume, bread volume, hardness index, flour water absorption, wet gluten percent, gluten index and sedimentation height were also measured. Data were analyzed using SAS 9.4 software, and the means were compared using the LSD test at the 5% probability level.

Results showed that the effect of salinity on grain yield and gluten index was significant. Grain protein content was not affected by salinity. The grain yields of Aftab, Aseman, Barzegar and Kohdasht cultivars in saline conditions were 527, 363, 447, and 207 g m-2, respectively; indicating 25, 33, 12 and 55% decreases compared to non-saline conditions. Literature generally confirms 15-30% decreases in wheat grain yield under irrigation with saline water of 8-10 dS m-1. Aftab as a dryland variety produced the highest grain yield, i.e. 617 g m-2. The grain yields of Barzegar, Aseman and Kohdasht were 23, 27 and 46% lower compared to Aftab, respectively. Due to irrigation cut-off and failure to complete the growth period, Barzegar had the lowest thousand kernel weight under both saline and non-saline conditions. The highest hectoliter weight and gluten index were observed in Aftab under both conditions. Grain protein was not affected by the irrigation water salinities. The value for grain protein content of the cultivars was around 11.45% without significant difference in both non-saline and saline conditions. The amount of leaf area index for all cultivars was lower in saline conditions than the non-saline conditions. Irrigation with saline water decreased the leaf area index of Aftab, Aseman, and Kohdasht cultivars by 41, 30, and 52% compared to non-saline condition, respectively. As the leaf area index has a major role in current photosynthesis for assimilate partitioning, its decrease leads to a decrease in plant above-ground dry mass, harvest index, and finally grain yield.

Based on the results, Barzegar as local check suffered more damage from drought stress in both saline and non-saline conditions due to its late maturity. Therefore, under similar situation, Aftab cultivar could be a suitable candidate for areas where water resources are both scarce and saline. In addition, early wheat varieties may be considered as an effective factor in selecting suitable cultivars for arid and semi-arid regions, regardless of salinity.