Lecturer Department of Horticulture, MNS-University of Agricluture, Multan-Pakistan Multan, Punjab, Pakistan
Body of Abstract: In subtropical areas, guava is a substantial fruit crop, but drought stress is reducing its production. Little is known how drought stress affects the underlying transcriptional regulation, morpho-physiological responses, and biochemical reactions in Pakistani guava. Therefore, in this study, two guava cultivars, "Gola" and "Surahi," were compared to see how effectively they responded to drought stress by evaluating the morpho-physiological and biochemical factors that were differentially regulated by expressed sequence tags (ESTs). Different field capacities (To = 100% (control), T1 = 75%, and T2 = 50%) with modified moisture levels were used during the study. Both cultivars displayed an overall reduction in morphological and physiological traits in their response to drought stress. The "Surahi" cultivar, however, showed improved water usage efficiency (41.86%), indicating stronger drought resistance, as evidenced by increased catalase (170.21%) and peroxidase (402%) activity under T2 (50% field capacity). The "Surahi" cultivar's resistance to drought stress was further strengthened by its higher proline and flavonoid levels. Comparative investigation showed that there were differences in the expression of ESTs, with the cultivar "Surahi" (234) showing a higher number than "Gola" (117). One consequence of these ESTs on improved morpho-physiological properties against drought stress was the overexpression of ESTs linked to alcohol dehydrogenase (ADH), ubiquitin, sucrose synthase (SUS), and peroxidase at morphological, biochemical, and physiological levels. Conclusively, the pear-shaped guava cultivar "Surahi's" ability to respond to drought stress is due to the overexpression of related ESTs and elevated activities of catalase (CAT) and peroxidase (POD).