Host plant resistance in common bean (Phaseolus vulgaris L.) is a promising component in an integrated cropping system for managing thrips (Thrips palmi Karny) infestation. This study was conducted to identify quantitative trait loci (QTLs) for resistance to thrips in common bean, using F 5:7 recombinant inbred lines (RILs) as a mapping population. The RILs, derived by single seed descent (SSD) of the cross of two Mesoamerican bean lines, BAT 881 and G 21212, were found to show transgressive segregation for thrips resistance in the field. Correlations between damage and reproductive adaptation (RA) scores were significant within and between seasons. The QTLs for both traits were located based on single interval mapping (IM) and joint interval mapping (JIM) analysis using a genetic map constructed with microsatellite and random amplified polymorphic DNA (RAPD) markers. Eight of eleven resulting linkage groups (LGs) were shown to be homologous to chromosomes of the integrated linkage map of common bean. A major QTL for thrips resistance located on LG b06 explained up to 26.8% of variance for resistance in a single season and was named Tpr6.1. The JIM across several seasons revealed various QTLs on LGs b02, b03, b06, and b08, some of which were located at regions of genes encoding for disease resistance. The identification and mapping of thrips-resistance genes is expected to facilitate the development of resistant bean cultivars by using molecular marker-assisted selection.

QTL mapping of resistance to Thrips palmi karny in common bean (Phaseolus vulgaris L.) [poster] [on line]

This study provides insights in patterns of distribution of abiotic and biotic stress resilience across Vigna gene pools to enhance the use and conservation of these genetic resources for legume breeding. Vigna is a pantropical genus with more than 88 taxa including important crops such as V. radiata (mung bean) and V. unguiculata (cowpea). Our results show that sources of pest and disease resistance occur in at least 75 percent of the Vigna taxa, which were part of screening assessments, while sources of abiotic stress resilience occur in less than 30 percent of screened taxa. This difference in levels of resilience suggests that Vigna taxa co-evolve with pests and diseases while taxa are more conservative to adapt to climatic changes and salinization. Twenty-two Vigna taxa are poorly conserved in genebanks or not at all. This germplasm is not available for legume breeding and requires urgent germplasm collecting before these taxa extirpate on farm and in the wild. Vigna taxa, which tolerate heat and drought stress are rare compared with taxa, which escape these stresses because of short growing seasons or with taxa, which tolerate salinity. We recommend prioritizing these rare Vigna taxa for conservation and screening for combined abiotic and biotic stress resilience resulting from stacked or multifunctional traits. The high presence of salinity tolerance compared with drought stress tolerance, suggests that Vigna taxa are good at developing salt-tolerant traits. Vigna taxa are therefore of high value for legume production in areas that will suffer from salinization under global climate change.

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Mapping patterns of abiotic and biotic stress resilience uncovers conservation gaps and breeding potential of Vigna wild relatives

Ensuring food and nutritional security in light of high climate variability and a rapidly growing population remains a challenge. Mungbean (Vigna radiata (L.) Wilczek) is a short duration, drought-tolerant, and ureide-exporting legume crop capable of symbiotic atmospheric nitrogen fixation. Estimates of biological N2 fixation by mungbean in different soil textures have not been extensively studied. We conducted this study to evaluate plant growth and N2 fixation of five mungbean genotypes (Berken, 8735, IC 8972-1, STB#122, 223) inoculated with Bradyrhizobium spp. and grown on loamy sand and silt loam soils under glasshouse conditions. Mungbean dry matter yield, δ15N values, shoot content, amounts of N-fixed, and soil N uptake were all higher on the silt loam soil compared to the loamy sand soil, demonstrating the effects of soil properties on plant growth and N2 fixation potential. Among genotypes, IC 8972-1 produced the highest biomass (7.85 g plant−1), shoot N content (200 mg plant−1), and soil N uptake (155 mg plant−1) than other genotypes. The significant interaction between soil texture and genotypes for root dry matter and %Ndfa indicates the major role of legume root-nodule bacteria in symbiotic N2 fixation. This study demonstrated that N2 fixation in mungbean is affected by both genotypes and soil properties, illustrating the need to consider soil properties in order to maximize N contribution from mungbean to agricultural production systems.

https://link.springer.com/content/pdf/10.1007/s42729-020-00290-2.pdf

Assessment of Nitrogen Fixation by Mungbean Genotypes in Different Soil Textures Using 15N Natural Abundance Method

Globally, yellow mosaic disease (YMD) remains a major constraint of mungbean production, and management of this deadly disease is still the biggest challenge Thus, finding ways to manage YMD including development of varieties possessing resistance against mungbean yellow mosaic virus (MYMV) and mungbean yellow mosaic India virus (MYMIV) is a research priority for mungbean crop Characterization of YMD resistance using various advanced molecular and biochemical approaches during plant-virus interactions has unfolded a comprehensive network of pathogen survival, disease severity, and the response of plants to pathogen attack, including mechanisms of YMD resistance in mungbean The biggest challenge in YMD management is the effective utilization of an array of information gained so far, in an integrated manner for the development of genotypes having durable resistance against yellow mosaic virus (YMV) infection In this backdrop, this review summarizes the role of various begomoviruses, its genomic components, and vector whiteflies, including cryptic species in the YMD expression Also, information about the genetics of YMD in both mungbean and blackgram crops is comprehensively presented, as both the species are crossable, and same viral strains are also found affecting these crops Also, implications of various management strategies including the use of resistance sources, the primary source of inoculums and vector management, wide-hybridization, mutation breeding, marker-assisted selection (MAS), and pathogen-derived resistance (PDR) are thoroughly discussed Finally, the prospects of employing various powerful emerging tools like translational genomics, and gene editing using CRISPR/Cas9 are also highlighted to complete the YMD management perspective in mungbean

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Yellow Mosaic Disease (YMD) of Mungbean (Vigna radiata (L.) Wilczek): Current Status and Management Opportunities.

BackgroundMungbean (Vigna radiata [L.] R. Wilczek) is an important legume crop with high nutritional value in South and Southeast Asia. The crop plant is susceptible to a storage pest caused by bruchids (Callosobruchus spp.). Some wild and cultivated mungbean accessions show resistance to bruchids. Genomic and transcriptomic comparison of bruchid-resistant and -susceptible mungbean could reveal bruchid-resistant genes (Br) for this pest and give insights into the bruchid resistance of mungbean.ResultsFlow cytometry showed that the genome size varied by 61 Mb (mega base pairs) among the tested mungbean accessions. Next generation sequencing followed by de novo assembly of the genome of the bruchid-resistant recombinant inbred line 59 (RIL59) revealed more than 42,000 genes. Transcriptomic comparison of bruchid-resistant and -susceptible parental lines and their offspring identified 91 differentially expressed genes (DEGs) classified into 17 major and 74 minor bruchid-resistance–associated genes. We found 408 nucleotide variations (NVs) between bruchid-resistant and -susceptible lines in regions spanning 2 kb (kilo base pairs) of the promoters of 68 DEGs. Furthermore, 282 NVs were identified on exons of 148 sequence-changed-protein genes (SCPs). DEGs and SCPs comprised genes involved in resistant-related, transposable elements (TEs) and conserved metabolic pathways. A large number of these genes were mapped to a region on chromosome 5. Molecular markers designed for variants of putative bruchid-resistance–associated genes were highly diagnostic for the bruchid-resistant genotype.ConclusionsIn addition to identifying bruchid-resistance-associated genes, we found that conserved metabolism and TEs may be modifier factors for bruchid resistance of mungbean. The genome sequence of a bruchid-resistant inbred line, candidate genes and sequence variations in promoter regions and exons putatively conditioning resistance as well as markers detecting these variants could be used for development of bruchid-resistant mungbean varieties.

Additional file 1: Table S1. of Genomic and transcriptomic comparison of nucleotide variations for insights into bruchid resistance of mungbean (Vigna radiata [L.] R. Wilczek)

Mungbean [Vigna radiata (L.) R. Wilczek var. radiata] is an important food and cash legume crop in Asia. Development of short duration varieties has paved the way for the expansion of mungbean into other regions such as Sub-Saharan Africa and South America. Mungbean productivity is constrained by biotic and abiotic factors. Bruchids, whitefly, thrips, stem fly, aphids, and pod borers are the major insect-pests. The major diseases of mungbean are yellow mosaic, anthracnose, powdery mildew, Cercospora leaf spot, halo blight, bacterial leaf spot, and tan spot. Key abiotic stresses affecting mungbean production are drought, waterlogging, salinity, and heat stress. Mungbean breeding has been critical in developing varieties with resistance to biotic and abiotic factors, but there are many constraints still to address that include the precise and accurate identification of resistance source(s) for some of the traits and the traits conferred by multi genes. Latest technologies in phenotyping, genomics, proteomics, and metabolomics could be of great help to understand insect/pathogen-plant, plant-environment interactions and the key components responsible for resistance to biotic and abiotic stresses. This review discusses current biotic and abiotic constraints in mungbean production and the challenges in genetic improvement.

Akmm Alam

Papers

Biotic and abiotic constraints in mungbean production-progress in genetic improvement.