Sorghum Water Extract Application Mediates Antioxidant Defense and Confers Drought Stress Tolerance in Wheat

Drought is the most threatening abiotic constraint, affecting more than 43% of the cropped area around the globe. The use of allelopathic hormesis offers a pragmatic solution for mitigating the negative effects of drought on field crops. The present study evaluated the potential of sorghum water extract in enhancing drought tolerance in wheat and examined the possible underlying mechanisms. The experiment comprised of three factors viz. drought with three levels (100%, 60% and 30% field capacity; FC), sorghum water extracts with eight levels (control, water spray, 0.5%, 1.0%, 1.5%, 2.0%, 2.5% and 3.0% of sorghum water extract) and two wheat cultivars Ihsan-2016 (drought tolerant) and Galaxy-2013 (drought-sensitive). Drought stress, particularly at 30% FC, profoundly decreased the morpho-physiological attributes of both wheat cultivars; nevertheless, the application of sorghum water extract at 2.0% effectively enhanced the tolerance against drought stress. Compared with control, application of 2.0% sorghum water extract increased the morphological attributes such as shoot and root length as well as fresh and dry weight of both wheat cultivars in the range of 3–146% under 30% field capacity. In addition, 2.0% sorghum water extract triggered (9–165%) the activities of superoxide dismutase, catalase, and peroxidase, decreased the hydrogen peroxide contents (42–48%), and enhanced the contents of chlorophyll a, b, and carotenoid (6–151%) as compared to control in both wheat cultivars under 30% field capacity suggesting that these measures helped to reduce the drought-induced oxidative stress. Vigorous growth and higher drought tolerance derived from sorghum water extract was related to improved chlorophyll contents and a better antioxidant defense system in wheat.