Abstract
To understand the physiological basis of tolerance to combined stresses to low phosphorus (P) and drought in mungbean (Vignaradiata (L.) R. Wilczek), a diverse set of 100 accessions were evaluated in hydroponics at sufficient (250 μM) and low (3 μM) P and exposed to drought (dehydration) stress. The principal component analysis and ranking of accessions based on relative values revealed that IC280489, EC397142, IC76415, IC333090, IC507340, and IC121316 performed superior while IC119005, IC73401, IC488526, and IC325853 performed poorly in all treatments. Selected accessions were evaluated in soil under control (sufficient P, irrigated), low P (without P, irrigated), drought (sufficient P, withholding irrigation), and combined stress (low P, withholding irrigation). Under combined stress, a significant reduction in gas exchange traits (photosynthesis, stomatal conductance, transpiration, instantaneous water use efficiency) and P uptake in seed and shoot was observed under combined stress as compared to individual stresses. Among accessions, IC488526 was most sensitive while IC333090 and IC507340 exhibited tolerance to individual or combined stress. The water balance and low P adaptation traits like membrane stability index, relative water content, specific leaf weight, organic acid exudation, biomass, grain yield, and P uptake can be used as physiological markers to evaluate for agronomic performance. Accessions with considerable tolerance to low P and drought stress can be either used as ‘donors’ in Vigna breeding program or cultivated in areas with limited P and water availability or both.
Highlights
The 100 mungbean accessions screened under different treatments in hydroponics culture for traits related to drought stress, biomass, root morphology, and P indices (P concentration and total plant P uptake) were evaluated
The traits contributing to this variation under low P stress were total dry weight, shoot dry weight, root dry weight, total root length, root surface area, root volume, moisture retention capacity, rate of water loss, number of root tips, and total plant P uptake
We systematically identified contrasting mungbean accessions from the diverse set based on their physiological performance under low P, drought, and combined stress conditions
Summary
Mungbean is preferred for its high nutritional value and for improving soil fertility. Phosphorus (P) is a non-renewable resource and the second most important macronutrient for plant growth and development after nitrogen (N). Deficiency of P has deleterious effects on plant growth, development, and reproduction. Limitation in plant growth and seed yield under P deficiency is mainly attributed to its heterogenous distribution and low mobility in soil. Most of the world’s arable lands exhibits high P retention potential that leads to poor bioavailability of P for plant uptake [2]. It is generally accepted that the uptake of P by crop plants is reduced in limited moisture condition through changes in mass flow and diffusion, reduced root proliferation, and by altered
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