Legume genetic resources and transcriptome dynamics under abiotic stress conditions

Grain legumes are an important source of nutrition and income for billions of consumers and farmers around the world. However, the low productivity of new legume varieties, due to the limited genetic diversity available for legume breeding programmes and poor policymaker support, combined with an increasingly unpredictable global climate is resulting in a large gap between current yields and the increasing demand for legumes as food. Hence, there is a need for novel approaches to develop new high-yielding legume cultivars that are able to cope with a range of environmental stressors. Next-generation technologies are providing the tools that could enable the more rapid and cost-effective genomic and transcriptomic studies for most major crops, allowing the identification of key functional and regulatory genes involved in abiotic stress resistance. In this review, we provide an overview of the recent achievements regarding abiotic stress resistance in a wide range of legume crops and highlight the transcriptomic and miRNA approaches that have been used. In addition, we critically evaluate the availability and importance of legume genetic resources with desirable abiotic stress resistance traits. Legume crop production is threatened by the increasing incidence of environmental stresses. Therefore, it is essential to intensify legume improvement programmes, by using advanced breeding approaches and techniques, to develop new high-yielding legume cultivars that are able to cope with a range of environmental stressors. In this review, we examine recent findings on (a) legume genetic resources as essential materials for understanding the genetic variations associated with abiotic stress resistance traits, (b) high-throughput phenotyping technologies that can be used for phenotyping of legumes under both controlled and field conditions during abiotic stresses, (c) legume next-generation sequencing-based transcriptomics as a prospective technique for in-depth coverage and gene expression atlas, and (d) miRNAs as an additional opportunity for the genetic improvement of abiotic stress resistance in legumes.