Mitigation of Abiotic Stress in Legume-Nodulating Rhizobia for Sustainable Crop Production
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REVIEW
Mitigation of Abiotic Stress in Legume-Nodulating Rhizobia for Sustainable Crop Production Swati Sindhu1 • Anupma Dahiya1 • Rajesh Gera1 • Satyavir Singh Sindhu1
Received: 3 May 2019 / Accepted: 4 March 2020 Ó NAAS (National Academy of Agricultural Sciences) 2020
Abstract Rhizobia form nitrogen-fixing nodules on leguminous plants and convert atmospheric nitrogen to plant-utilizable ammonia resulting into increased plant growth and crop yield. The growth of crops and rhizobia is adversely affected by various abiotic stresses including high temperature, soil salinity and drought. Under saprophytic phase in the soil, freeliving rhizobial population usually declines due to abiotic stresses resulting to less nodulation in different legumes. Therefore, repeated inoculation is required every year for enhancing legume productivity. For effective nodulation, establishment and persistence of rhizobia in stressed environment is prerequisite, which depends mainly on their ability to tolerate, proliferate and survive under adverse environmental conditions. The major problem of abiotic stresses is faced in rainfed agro-ecosystems, which makes the survival of bio-inoculants a problematic issue. Moreover, a remarkable difference was observed in effectiveness of rhizobial bio-inoculants from laboratory to field conditions due to various abiotic stresses faced under field conditions. The survival of rhizobial inoculants and its limitations to enhance crop growth under field conditions may be overcome by screening the rhizobial isolates, which are tolerant to different types of stressed conditions. Stress-tolerant rhizobia could provide more beneficial effects under pot house and field trials leading to increased legume crop productivity in sustainable agriculture. Keywords Rhizobia Abiotic stress Temperature Drought Salinity Nutrient acquisition Crop productivity
Introduction Intensive use of agricultural lands for cultivation of exhaustive crops has resulted in decline of soil fertility and environmental degradation. Besides this, crop production under field conditions is often limited by exposure to various abiotic stresses such as drought, heat stress, cold, frost and soil salinity [3, 165]. These abiotic stress conditions severely affect the biochemical and physiological parameters along with morphology of the crop plants [42]. Microorganisms inhabiting the soil and rhizosphere under stress environments are being exploited recently for & Satyavir Singh Sindhu [email protected] 1
Department of Microbiology, CCS Haryana Agricultural University, Hisar, Haryana 125 004, India
amelioration of stress effects leading to sustainable crop productivity [77]. However, the proliferation and survival of beneficial soil/rhizosphere microbiome [88, 94, 166] and the contributions of these microbial inoculants under stress conditions are often not realized, resulting in low crop yields [19, 59, 85]. The estimated yield loss for major crops including legumes could be up to 50% under adverse stress conditions. Recent en
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