Selection of tolerant barley (Hordeum vulgare L.) genotypes to terminal drought stress based on grain yield, yield stability and stress tolerance indices

Among the cereal crops, barley is known as the fourth most important crop on a global scale and provides about 50% of the calories needed in the world. This plant can even make up to 70% of calories in less developed countries, especially in Africa and Asia. Terminal drought stress, as one of the consequences of climate change, has significant negative effects on the crop plants’ growth and production. Considering the importance of barley as livestock feed and its role in food industry, development and introduction of drought stress tolerant barley cultivars is very important. To increase the levle of terminal drough tolerance, breeders should combine the improvement of grain yield along with high level of terminal drought tolerance. To reach this goal first step in this way is to select potential germplasm that have genotypic variation for drought tolerance.

Eighteen barley promising genotypes were evaluated for adaptation, grain yield  and yield stability under none-stress and terminal drought stress condtions (withholding irrigation from the 50% spike emergence stage)  using randomized complete blocks design with three replications in three research field stations; Varamin, Birjand and Yazd, Iran, in two cropping seasons (2020-21 and 2021-22). None-stress and stress experiments were carried out separately. In non-stress conditions, full irrigation was applied, and in terminal drough stress conditions, irrigation was withheld at the 50% spike emergence stage. The barley promising genotypes were selected from the advance barley grain yield comparison trial genotypes in the temperate zone stations of the country in the previous cropping season. After determining the grain yield in two conditions of none stress and drought stress, the stress indices including; MP, GMP, TOL, HARM, STI, YI, YSI, RSI and SSI as well as their correlation with grain yield were calculated using the iPASTIC program and the three-dimensional distribution diagram of genotypes in A, B, C and D ranges was drawn using Grapher software. Combined analysis of variance was performed to study genotypic variation and genotype × year interaction effect. Least significant difference (LSD) test was employed for mean comparison at the 5% propbabilty level. Different stability statistics as well as their relationships were calculated using Pearson correlation using STABILITYSOFT program.

The results showed that YI, HM, GMP, STI and MP indices can be used to select barley genotypes adapted and suitable for areas that are prone to terminal drought season stress. In non-stress areas MP, STI, GMP, HM, TOL and SSI indices can be used for selection of suitable and adapted cultivars. According to the biplot diagram, genotypes 2, 3, 11, 12 and 15 had higher grain yield and terminal drough tolerant. Considering mean grain yield, yield stability statistics, and standard deviation of the rank of each of these statistics, genotypes 11, 8, 3, 6 and 15 had higher grain yield stability.

Considering mean grain yield, all stability statistics and stress indices, genotype no. 11 with pedigree of GS679.82/SHYRI//LAUREL/4/CERISE/SHYRI//… /5/MALOUH//Aths/ Lignee686/6/Nik, genotype no. 8 with pedigree  of Anoidium//Alanda/Hamra-01/3/Lignee527/NK1272//JLB70-63/4/Nik, genotype no. 3 with pedigree of 82S:510/3/Arinar/Aths//DS 29/4/Sahra, genotype no. 6 with pedigree of Bgs/Dajia//L.1242/3/(L.B.IRAN/Una8271//Gloria'S'/3/Alm/Una80//....)/4/Sahra and genotype no. 15 with  pedigree of Ashar/Beecher/5/Lignee 527/Chn-01//Gustoe/4/Rhn-08/3/Deir Alla 106//Dl71/Strain 205 as superior genotypes that are suitable for cultivation in none-stress as well as terminal drought stress conditions in temperate agro-climate zone.