Abstract
Grain legumes are a key food source for ensuring global food security and sustaining agriculture. However, grain legume production is challenged by growing disease incidence due to global climate change. Ascochyta blight (AB) is a major disease, causing substantial yield losses in grain legumes worldwide. Harnessing the untapped reserve of global grain legume germplasm, landraces, and crop wild relatives (CWRs) could help minimize yield losses caused by AB infection in grain legumes. Several genetic determinants controlling AB resistance in various grain legumes have been identified following classical genetic and conventional breeding approaches. However, the advent of molecular markers, biparental quantitative trait loci (QTL) mapping, genome-wide association studies, genomic resources developed from various genome sequence assemblies, and whole-genome resequencing of global germplasm has revealed AB-resistant gene(s)/QTL/genomic regions/haplotypes on various linkage groups. These genomics resources allow plant breeders to embrace genomics-assisted selection for developing/transferring AB-resistant genomic regions to elite cultivars with great precision. Likewise, advances in functional genomics, especially transcriptomics and proteomics, have assisted in discovering possible candidate gene(s) and proteins and the underlying molecular mechanisms of AB resistance in various grain legumes. We discuss how emerging cutting-edge next-generation breeding tools, such as rapid generation advancement, field-based high-throughput phenotyping tools, genomic selection, and CRISPR/Cas9, could be used for fast-tracking AB-resistant grain legumes to meet the increasing demand for grain legume-based protein diets and thus ensuring global food security.
Highlights
Grain legumes are a cheap source of plant-based dietary protein and vital micronutrients and vitamins for the human population, lowering the risk of heart-related diseases and type 2 diabetes, and playing a crucial role in reducing global food insecurity and eradicating malnutrition-related problems [1,2,3]
Classical genetic studies have revealed the genetics of Ascochyta blight (AB) resistance in various grain legumes, evidenced by monogenic inheritance controlled by a single dominant gene [19,20,23,83], single recessive gene [21,22,23,24,84], or digenic inheritance [25,26,27]
Jha et al [128] mapped nine AB-resistant quantitative trait loci (QTL) explaining 7.5–28% Phenotypic Variation (PV) from a P651 (P. fulvum) and Alfetta (Pisum sativum L.) interspecific RIL-based mapping population. Of these QTL, two abIII-1 and abI-IV-2 were consistent across the tested locations and years and later fine mapped using GBS-derived single nucleotide polymorphisms (SNP) markers by genotyping heterogeneous inbred family (HIF)-224 and HIF-173 derived from F6 RILs of PR-19-224 and PR-19-173 [141]
Summary
Grain legumes are a cheap source of plant-based dietary protein and vital micronutrients and vitamins for the human population, lowering the risk of heart-related diseases and type 2 diabetes, and playing a crucial role in reducing global food insecurity and eradicating malnutrition-related problems [1,2,3]. Various biotic stresses, including Ascochyta blight (AB), a fungal foliar disease belonging to the class Dothideomycetes, order Pleosporales, and family Didymellaceae [4], cause significant yield losses in various grain legumes across the globe [5,6,7,8,9,10,11]. Symptom appears as necrotic lesions on leaves, stems, and pods, inhibiting photosynthesis and causing up to 70% seed yield losses [5]. AB infection starts at the seedling stage and spreads across aerial parts; visual symptoms include necrotic leaf spots, chlorotic halos in leaves, stem and pod lesions, and dark brown discoloration of seeds [44,64,65,66] (see Table 1). AB disease symptoms appear as necrotic lesions on leaves, stems, and pods, inhibiting photosynthesis and causing up to 70% seed yield losses [5]. The disease symptoms are characterized by necrotic lesions on the stems and leaves [39]
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