Salinity stress is one of the important abiotic stresses affecting rice germination and reduces establishment of seedlings in the field. Six varieties of rice were included in a full diallel mating design and together with their progenies were evaluated for salinity tolerance. General combining ability (GCA) effect was significant for germination percentage reduction (GP) and radicle length reduction (RL); whereas specific combining ability (SCA) were significant for all of traits contain GP, RL, germination rate reduction (GR) and coleoptile length reduction (CL). The negative value of heterosis, due to inverse relation of reduction of traits and salinity tolerance, indicated ideal heterosis. The highest value of negative heterosis for GP, GR, RL and CL were displayed in Shahpasand × Sepidrod, Hassani × Sepidrod, Shahpasand × IRFAON-215 and Sepidrod × IRFAON-215, respectively. The parents with negative GCA are superior for salinity tolerance traits. The Genotype, Genotype-by-Environment (GGE) biplot analysis showed that Sepidrod contributed resistance to GP, GR and IRFAON-215 was the best parent for RL and CL. Respondent this view, Sepidrod and IRFAON-215 can be used either as best parents for selection programs due to their GCA effects, or as a superior parent hybrid programs on their SCA effects.
Drought is one of most important environmental factors inhibiting photosynthesis and decreasing growth and productivity of plants. The sensitivity of crop plants such as wheat to soil drought is particularly serious during reproductive phase is extremely sensitive to plant water status. The aim of this work was to study the effects of drought stress on photosynthesis, photosynthetic pigments, soluble proteins, a-tocopherol and abscisic acid content in six wheat genotypes, two tolerant (Daric and 92 Zhong), two moderately tolerant (Sabalan and DH-2049-3) and two sensitive (Shark and Tevee’s’). Total chlorophyll content, relative water content and chlorophyll a/b ratio decreased after long-time drought stress, that decrease in sensitive genotypes was higher than others. Net photosynthesis and stomatal conductance decreased significantly (P < 0.05) in flag leaves of our genotypes under drought stress after pollination, that decrease in sensitive genotypes was higher, too. Abscisic acid content, soluble protein content and a-tocopherol increased under drought stress, that increase in tolerant genotypes was higher. There was a significant negative correlation (P < 0.05) between photosynthesis factors and abscisic acid content in flag leaves of all genotypes. It can be concluded that Daric and 92 Zhong had a better photosynthesis factors compared to other genotypes and showed a higher capacity to tolerate drought stress.