Higher activity of monodehydroascorbate reductase and lower activities of leaf and spike vacuolar invertase and glutathione S-transferase reveals higher number of grains per spike in spring wheat genotypes grown under well-watered and drought conditions

Abstract

Background: To improve our understanding about the physiological mechanism of grain yield reduction at anthesis, three spring wheat genotypes (L1, L2 and L3) having contrasting yield potential under drought in field were investigated under controlled greenhouse conditions., drought stress was imposed at anthesis stage by withholding irrigation until all plant available water was depleted, while well-watered control plants were kept at 95% pot water holding capacity. Results: Compared to genotype L1 and L2, pronounced decrease in grain number (NGS), grain yield (GY) and harvest index (HI) were found in genotype L3, mainly due to its greater kernel abortion (KA) under drought. A significant positive correlation of leaf monodehydroascorbate reductase (MDHAR) with both NGS and HI was observed. In contrast, significant negative correlations of glutathione S-transferase (GST) and vacuolar invertase (vacInv) both within source and sink with NGS and HI were found. Likewise, a significant negative correlation of leaf abscisic acid (ABA) with NGS was noticed. Moreover, leaf aldolase and cell wall peroxidase (cwPOX) activities were significantly and positively associated with TKW. Conclusion: Collectively, distinct physiological markers were correlating with yield traits and higher activity of leaf aldolase and cwPOX may be chosen as predictive bio-markers for higher TKW. Also, higher activity of MDHAR within the leaf can be selected as a predictive bio-marker for higher NGS in wheat under drought. Whereas, lower activity of vacInv and GST both within leaf and spike can be selected as bio-markers for higher NGS and HI. The results highlighted the role of antioxidant and carbohydrate-metabolic enzymes in the modulation of source-sink balance in wheat crops, which could be used as bio-signatures for breeding and selection of drought-resilient wheat genotypes for a future drier climate.