Soybean production and drought stress

Abstract Soybean ( Glycine max (L.) Merr.) contributes 57% of the total oilseed production worldwide. Like many other crop species, sustainability of its production is severely challenged by drought, depressing up to 40% of the yield annually. Also, the changing climate further exacerbates the situation. To overcome this challenge, conventional and genomic approaches together with bioinformatics tools have been utilized for understanding drought tolerance mechanisms followed by utilization of this information for developing drought-tolerant soybean cultivars. Selection of drought-tolerant varieties based on physiological attributes assisted with genomic approaches is one of the methods focused on. Among the morphological and physiological attributes to be taken into account, root traits and capability of nitrogen fixation under drought stress (water-limited) have been extensively used for selecting drought-tolerant genotypes. At the onset of the twenty-first century, the availability of genetic maps, QTLs associated with multiple traits, and the genome sequence information of soybean have made possible the initiation of breeding by designed programs. Although studies on QTL mapping are not explicit, the availability of numerous markers like SNPs and new techniques like “Meta QTLs” are promising for utilizing this information in marker-assisted selection. Identification of drought-responsive genes, transcription factors, and development of transgenic soybean are new horizons for combating drought stress. For example, transcription factors including DREBs, ERFs, ZIP, WRKY, and MYB have been identified in soybean and are overexpressed in various model plant species to enable evaluation of their role under drought conditions. There are few reports on development of transgenic soybean with the enhanced drought stress tolerance. The P5CR gene and DREB1D transcription factor isolated from Arabidopsis and the NTR1 gene isolated from Brassica campestris (encoding jasmonic acid carboxyl methyltransferase) were introduced into soybean, which resulted in improved tolerance to water-limited conditions. Collaborative efforts involving bridging the conventional breeding and newer genomic methods, including use of targeting-induced local lesions in genomes and next generation sequencing assays, would pave the way for developing drought resilient cultivars.