Cross tolerance to phosphorus deficiency and drought stress in mungbean is regulated by improved antioxidant capacity, biological N2‑fixation, and differential transcript accumulation

Abstract

Aims: Phosphorus (P) mobility depends on the availability of water in soil, both of which are limited resources for crop production. We studied the mechanisms governing tolerance to P-deficiency and drought stress in contrasting mungbean accessions. Methods: Tolerant (IC333090 and IC507340) and sensitive (IC488526 and EC397142) mungbean accessions were grown in soil under four treatments: control (sufficient P, irrigated), P-deficiency (no P, irrigated), drought (sufficient P, irrigation withheld), combined stress (no P, irrigation withheld), followed by a 48 h recovery. Results: Drought stress reduced the relative water content and membrane stability index, affecting overall plant growth. The tolerant accessions maintained significantly higher root growth, leaf area, and biomass under combined stress (P-deficiency and drought) than the sensitive accessions, mainly due to enhanced nutrient uptake and symbiotic N2-fixation. The combined stress also increased osmolyte concentration, antioxidative compounds, and the scavenging activity of antioxidant enzymes in tolerant accessions. Recovery from drought stress significantly reduced osmolyte concentration. Transcript abundance of candidate genes related to P-deficiency and drought under individual and combined stress, was significantly higher in leaves of IC333090 than IC488526. IC333090 recovered from drought stress better than IC488526 due to the enhanced expression of stress responsive genes. Conclusions: Physiological traits, such as the accumulation of total soluble sugars and reduced glutathione, ascorbate, and scavenging activity of antioxidant enzymes, facilitated by the differential expression of stress responsive genes impart cross-tolerance to P-deficiency and drought stress in tolerant mungbean accessions. Hence, accession IC333090 is potential genetic stock for tolerance to drought, P-deficiency, and combined stresses.