Evaluation of Mulberry Genotypes Under Moisture Stress for the Identification of Physio-biochemical Markers of Stress Tolerance

Identification of tolerant mulberry genotypes and elucidation of stress-tolerant mechanisms are two priority areas need to be addressed for sustainable mulberry leaf production. In the present study, 16 mulberry genotypes were evaluated under at low (75% FC), medium (50% FC), and high moisture stress (25% FC) conditions along with well-irrigated plants (100% FC) and measured the photosynthetic efficiency and antioxidant potential. In well-irrigated plants, photosynthetic rate was high in S13 (16.45 µmol/m 2 /s), Mysore Local, RC2, and AGB8 (13.62–16 µmol/m 2 /s). All genotypes showed a gradual decline in photosynthetic rate during the progression of moisture stress (low to high stress). MSG2, AGB8, RC1, RC2, and Nagalur Estate showed high photosynthetic rate (7.45–10.15 µmol/m 2 /s) under high moisture stress, whereas low photosynthetic rate was recorded in Mysore Local (3.46 µmol/m 2 /s) and K2 (3.50 µmol/m 2 /s). All tolerant genotypes showed higher activities of SOD (104.25–122.44 Units/g) and POX (25.61–33.73 Units/g) activities under high moisture stress. Bundi-3, S34, RC2, and AGB8 showed higher SOD activity and low enzyme activity was observed in K2. Non-enzymatic antioxidants and osmolytes were high in moisture stress-tolerant genotypes. This study identified that high photosynthetic rate is one of the important physiological indicator for moisture stress tolerance in mulberry. Also higher activities of antioxidant enzymes (SOD and POX), presence of high quantity of non-enzymatic antioxidants (ascorbic acids, reduced glutathione, and phenols), and accumulation of osmolytes (proline and glycine betaine) are identified as stress tolerance biochemical markers in mulberry genotypes. Evaluation Index (EI) value was calculated and genotypes suitable for well-irrigated condition as well as for low, medium, and high moisture stress conditions were identified based on EI values.