Assessment of grain yield, water productivity and salinity tolerance in bread wheat elite lines

Salt stress affects 20% of global cultivable land and is increasing continuously owing to the change in climate and anthropogenic activities. Globally, wheat is cultivated on non-saline and saline soils, covering an area of approximately 214.79 million hectares (Becker-Reshef et al., 2020). Salinity stress negatively affects the growth and development of wheat leading to diminished grain yield and quality. For this reason, it is important to develop effective strategies to improve yield through salt tolerance. The breeding of salinity-tolerant cultivars through selection and breeding techniques is one of the effective methods in the production and exploitation of saline soil and water.

In order to study the effects of salinity stress on grain yield, phenological and morphological traits and salinity tolerance indices among bread wheat elite lines, two separate experiments in a randomized complete block design with three replications were conducted in two saline and normal environments during two cropping years of 2019-2021. 20 wheat cultivars and elite lines cultivated at the South Khorasan Agricultural and Natural Resources Research and Education Centre. After determining the grain yield in both conditions, MP, GMP, TOL, HARM, STI and SSI indices were calculated and using SAS software, their correlation with grain yield was investigated and using STATISTICA software, the three-dimensional distribution of each cultivar and line was plotted. Combined analysis of variance was performed to determine the main and interaction effects in the two years of the experiment and the means were compared by Duncan's multiple range test at the level of 5% probability. Bartlett's uniformity test was performed before the combined analysis of variance. Analysis of variance and mean comparison was performed using SAS-9.0 software and cluster analysis was performed by Ward method through StatGraphics program.

The reaction of wheat lines were different in two environments and salinity stress reduced grain yield. The experimental results showed that different wheat lines react differently to salinity stress. Salinity stress decreased grain yield and morphological traits in all lines compared to normal conditions. Salinity stress shortens intermediates and reduces plant height and consequently leaf and shoot dry weight by reducing cell proliferation and reducing dry matter accumulation (Dura et al., 2011).The difference between cultivars and lines in terms of all phenological, morphological and grain yield in two years of the experiment was significant, which indicates the existence of appropriate diversity in the wheat elite lines. The existence of this genetic diversity can be very useful for selecting high-yielding wheat cultivars in salinity conditions. In the first year of implementation, Narin, line No. 3 and Barzegar with an average of 6494, 6227 and 6072 kg/ha, respectively, in normal conditions and Barzegar, line No. 18 and Narin with an average of 6361, 6166 and 5805 kg/ha respectively, had the highest grain yield under salinity stress. In the second year of the experiment, line number 16, 10 and 4 with an average of 5388, 5305 and 5155 kg/ha in normal condition and Narin, Barzegar and line No. 3 with an average of 4930, 4611 and 4180 kg/ha respectively, had the highest grain yield under salinity stress. Naturally, wheat lines grain yield under salinity stress was lower than their yield under normal conditions. Under these conditions, the plant leaf area of is greatly reduced, which reduces the photosynthetic capacity of the plant, and as a result, the amount of dry matter produced and ultimately the grain yield of the plant is reduced (Munns et al., 2002).

For selecting wheat cultivars and lines in the areas that are most exposed to salinity stress, YI, HM, GMP, STI, MP, RSI and YSI indices and in areas not exposed to salinity stress, MP and STI indices are suggested. Barzegar and Narin check cultivars and line number 10 were determined as the most tolerant and lines No. 14, 13 and 20 as the most sensitive lines to salinity stress by different indices. Cluster analysis of lines based on STI index led to the placement of Barzegar and Narin cultivars and lines No. 3, 4 and 18 in the first cluster in which the mentioned lines have fewer days to heading and in contrast more days to maturity, grain filling period, thousand-grain weights and higher grain yield.