Abstract
Drought is one of the significant abiotic stresses threatening crop production worldwide. Soybean is a major legume crop with immense economic significance, but its production is highly dependent on optimum rainfall or abundant irrigation. Also, in dry periods, it may require supplemental irrigation for drought-susceptible soybean varieties. The effects of drought stress on soybean including osmotic adjustments, growth morphology and yield loss have been well studied. In addition, drought-resistant soybean cultivars have been investigated for revealing the mechanisms of tolerance and survival. Advanced high-throughput technologies have yielded remarkable phenotypic and genetic information for producing drought-tolerant soybean cultivars, either through molecular breeding or transgenic approaches. Further, transcriptomics and functional genomics have led to the characterisation of new genes or gene families controlling drought response. Interestingly, genetically modified drought-smart soybeans are just beginning to be released for field applications cultivation. In this review, we focus on breeding and genetic engineering approaches that have successfully led to the development of drought-tolerant soybeans for commercial use.
Highlights
Soybean, an important legume, is one of the most widely grown food crops in the world due to its valuable seed composition
Vast genetic diversity has been reported in soybean germplasm, and the increasing availability of soybean genetic resources has instigated the development of drought-smart soybeans (Carter et al, 2016; Ribichich et al, 2020; Kajiya-Kanegae et al, 2021; Chen L. et al, 2021)
Modern breeding and advanced biotechnology methods have shown promising results, and market-ready drought-tolerant soybeans have been released in some parts of the world (Carter et al, 2016; Ribichich et al, 2020)
Summary
An important legume, is one of the most widely grown food crops in the world due to its valuable seed composition. Shi et al (2018) identified a drought-responsive soybean WRKY gene, GmWRKY12, whose over-expression in a transgenic hairy root assay led to increased proline levels under drought stress. Chen H. et al (2021) identified QTLs related to primary root length on chromosome 16 of soybean This QTL accounts for 30.25% variation in phenotype and will assist in developing of markers for root-length selection, which is an important trait for drought tolerance. Dhungana et al (2021) identified QTLs associated with flooding stress at the V1-V2 stage of soybean They analysed a recombinant inbred line (RIL) population derived from crossing a drought-susceptible (NTS116) and drought-tolerant (Danbaekkong) soybean cultivar. HaHB4 is a water-deficit responsive sunflower transcription factor whose over-expression in Arabidopsis led to improved drought tolerance (Manavella et al, 2008). Co-inoculation of rhizobia and mycorrhizal fungi has shown enhanced soybean tolerance to drought stress providing a costeffective strategy for improving soybean productivity (Igiehon et al, 2021)
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