Effect of Exogenously Applied Jasmonic Acid and Kinetin on Drought Tolerance of Wheat Cultivars Based on Morpho-Physiological Evaluation

The population acceleration and better lifestyle submit new challenges for wheat researchers to breed wheat (Triticum sativum) cultivars with upgraded yield, quality, and resistance against abiotic stresses such as drought, so exploiting all available natural relatives of cultivated wheat and introducing even sensitive ones may be a useful approach to save time and efforts. Normally, the seedling stage is highly drought vulnerable, but for sensitive cultivars, the situation is more frustrating. We examine the potentiality of two regulating hormones in the upregulation of two wheat cultivars varying in their drought susceptibility at the seedling stage comparatively evaluated by morpho-physiological traits as indicators of drought tolerance. All the studied traits revealed cultivar-dependent variation in response to water deficit where cv. Sids 1 was tolerant and cv. Beni-suef 5 was sensitive. Shoot/root ratio, total water content, total dry weight, chlorophyll stability, total osmotic potential, osmoregulatory components, viz., soluble carbohydrates, soluble proteins and proline, membrane damage trait in terms of LOX, antioxidant defense system enzymatically in terms of APX, CAT, POD, SOD, and total antioxidant as drought tolerance indicators were the troubling shot due to water shortage in both cultivars. The damaging impacts of water deficit on these traits were conceived for sensitive cultivar compared with the tolerant one. Exogenous application of jasmonic acid (JA) or kinetin (K) efficiently conferred drought tolerance to sensitive cultivar to withstand harsh conditions in earlier stages and to perform comparably with tolerant ones. Applied hormones prompted unequivocal inversion from a state of downregulation to upregulation regarding all drought tolerance traits via reallocation of photoassimilates to vegetative sinks, thus promoting growth, increasing the accumulation of some osmoregulation compounds and thus increased tissue vigor and regulated the activity of antioxidant enzymes as well as morphological modulation attained by the restoration of shoot/root ratio. The results would promisingly be supportive of research programs seeking to develop anti-drought stress practices for sensitive wheat cultivars.