Cross Tolerance to Drought and low Phosphorus Stress in Mungbean is Regulated by Improved Antioxidant Capacity, Biological N2-Fixation, and Differential Transcript Accumulation

Abstract Aims The mobility of phosphorus (P) depends on availability of water in soil; both are limited resources for crop production. We studied the mechanisms governing cross tolerance in the contrasting mungbean accessions for drought and low P stress. Methods Tolerant (IC333090 and IC507340) and sensitive (IC488526 and EC397142) mungbean accessions were grown in soil with treatments: control (sufficient P, irrigated), low P (no P, irrigated), drought (sufficient P, irrigation withheld), and combined stress (no P, irrigation withheld) as well as recovery. Results Drought reduced the relative water content and membrane stability index, affecting overall plant growth. Combined stress (low P and drought) significantly increased root growth, leaf area, and biomass in tolerant accessions, which was attributed to enhanced nutrient uptake and symbiotic N 2 -fixation. Combined stress also increased osmolyte concentration, antioxidative compounds, and scavenging activity of antioxidant enzymes in tolerant accessions while recovery from drought significantly reduced osmolyte concentration. Transcript abundance of candidate genes related to drought and low P was significantly higher in leaves of IC333090 than IC488526. Conversely, low-P-induced genes ( VrSPX1 , VrPHO1 , VrSQD1, VrPEPCase , and VrMDH ) in IC488526 were either downregulated or did not significantly change under combined stress. The drought recovery was better in IC333090 due to enhanced expression of stress-responsive genes. Conclusions Tolerant mungbean accession could be used as potential donor parents in breeding programs. Traits imparting cross tolerance to drought and low P stress may facilitate better varietal selection for increased crop productivity under low P, drought, and the combined stress.