Effect of Water Deficit at The Reproductive Stage on Different Forage Sorghum Cultivars

Sorghum is of the most important forage plants with high production potential, the ability to grow in areas with poor soil, and high adaptation to stresses. To assess the effect of water deficit stress, the production potential and the relationship between important traits, 36 forage sorghum cultivars were studied under water deficit condition using a 6×6 Lattice design at the research farm of Shahid Bahonar University of Kerman in May, 2020. Water deficit was applied at the beginning of heading stage by irrigating at 85% depletion of soil available water. The non-stress conditions consisted of irrigation when 50% of the total available water was depleted from the root zone. The ANOVA showed that water deficit significantly reduced fresh forage yield and plant height by 44.80 and 18.28%, respectively. Cultivars unl Hybrid3, Wray, Speed Feed, and Smith had the highest fresh forage yields in both moisture conditions. Mean comparisons of MP, YI, GMP, and STI indices and principal component analysis for different indices showed that unl Hybrid3, Speed Feed, Wray, Smith, ICSV 25264, and Dale were as tolerant and high yielding cultivars in both moisture conditions. Based on the results of path analysis, plant height and stem diameter had the most direct effect on fresh forage yield under non-stress and water stress conditions, respectively. They had the most indirect effect on sorghum fresh forage yield through stem diameter and plant height, respectively. It may be concluded that water stress at the reproductive growth stage significantly reduced the growth and forage yield of sorghum. However, sufficient variation in the studied germplasm suggested the possibility of selection for more tolerant cultivars. The more tolerant cultivars with high yield potential in the studied germplasm may be proposed for cultivation in regions with limited water resources and traits identified effective on yield increase are suggested for breeding objectives.