​Advances in Molecular Breeding for Bruchid (Callosobruchus spp.) Resistance in Mungbean [Vigna radiata (L.) Wilczek]: A Review

Mungbean is one of the most important grain legumes with high-quality dietary protein in India as well in many other Asian countries. But the crop is severely affected by bruchids (Callosobruchus spp.) from field to storage condition. These storage pests not only affect the yield but also reduce the market value and quality of the crops. The chemical method of bruchid management is not economical and environmentally unsafe. So, the host-plant resistance to bruchids would be the best alternative and most sustainable way to control the bruchid. A very limited number of wild accessions and cultivated genotypes are available for the transfer of bruchid resistance gene through conventional breeding. Thus, insights into the molecular mechanism of resistance will help to find out the resistance genes/QTLs easily with the support of available genome sequence and that can be introgressed to the cultivated varieties through marker-assisted backcross breeding (MABB) approach. Therefore, in this review, we focused on QTL mapping, identification of novel QTLs, marker assisted-selection, genomics and transcriptomics study by using advanced molecular tools which will be very helpful for genomic-assisted breeding in mungbean for bruchid resistance.

Identification of a candidate gene for bruchid resistance by combining fine mapping and transcriptome profiling in mung bean (Vigna radiata L.)

Bruchids or seed weevils are serious storage insect pests of mung bean and other pulses. Though bruchid-resistant mung bean germplasm accessions are screened out, the molecular mechanisms of bruchid resistance in mung bean are still unclear. In this study, a segregating population with 182 RILs plants was developed; delimit the controlling gene to a 111-kb physical interval, in which 11 genes were predicted. Vr04g00919 encoding the function of a polygalacturonase inhibitor, was the most likely candidate genes. Here, sequence analysis of the candidate gene coding regions revealed that it has six SNPs between the parental lines and three SNPs resulted in amino acid changes. Sequence alignment revealed that one of these three SNPs are located in a conserved leucine rich repeat (LRR) domain, which is essential for the function of the protein. Subcellular localization of the VrPGIP2-GFP fusion protein indicated that the candidate gene PGIP2 is located in the nucleus and cytosol. RNA-seq and quantitative real-time PCR (qRT-PCR) analysis indicated that many defense responses, cell wall synthesis, biotic and abiotic stresses, and hormone synthesis were greatly activated in the bruchid resistance plants. These findings contribute to the molecular marker assisted selection of bruchid resistance cultivars.

Cicer turcicum: A New Cicer Species and Its Potential to Improve Chickpea

Genetic resources of the genus Cicer L. are not only limited when compared to other important food legumes and major cereal crops but also, they include several endemic species with endangered status based on the criteria of the International Union for Conservation of Nature. The chief threats to endemic and endangered Cicer species are over-grazing and habitat change in their natural environments driven by climate changes. During a collection mission in east and south-east Anatolia (Turkey), a new Cicer species was discovered, proposed here as C. turcicum Toker, Berger & Gokturk. Here, we describe the morphological characteristics, images, and ecology of the species, and present preliminary evidence of its potential utility for chickpea improvement. C. turcicum is an annual species, endemic to southeast Anatolia and to date has only been located in a single population distant from any other known annual Cicer species. It belongs to section Cicer M. Pop. of the subgenus Pseudononis M. Pop. of the genus Cicer L. (Fabaceae) and on the basis of internal transcribed spacer (ITS) sequence similarity appears to be a sister species of C. reticulatum Ladiz. and C. echinospermum P.H. Davis, both of which are inter-fertile with domestic chickpea (C. arietinum L.). With the addition of C. turcicum, the genus Cicer now comprises 10 annual and 36 perennial species. As a preliminary evaluation of its potential for chickpea improvement two accessions of C. turcicum were field screened for reproductive heat tolerance and seeds were tested for bruchid resistance alongside a representative group of wild and domestic annual Cicer species. C. turcicum expressed the highest heat tolerance and similar bruchid resistance as C. judaicum Boiss. and C. pinnatifidum Juab. & Spach, neither of which are in the primary genepool of domestic chickpea. Given that C. arietinum and C. reticulatum returned the lowest and the second lowest tolerance and resistance scores, C. turcicum may hold much potential for chickpea improvement if its close relatedness supports interspecific hybridization with the cultigen. Crossing experiments are currently underway to explore this question.

Efficacy of Natural Plants Extract and Ethnomedicinal Dilution on Bruchid (Callosobruchus maculatus) Management in Storage Mungbean [Vigna radiata (L.) Wilczek]

Background: Storage of pulse grain is a severe on-going problem for farmers, traders and also the consumers. Mungbean [Vigna radiata (L.) Wilczek] is one of such vital protein rich pulse crops of Indian origin referred to as poor man’s meat. Bruchids (Callosobruchus maculatus) (Coleoptera: Bruchidae) are the major polyphagous storage pest of mungbean which causes the substantial post-harvest qualitative and quantitative loss, especially in long time storage condition. This loss directly affects the agricultural economy and also the human health.Methods: To find a solution, we first screened a large variety of mungbean genotypes against bruchid attack and narrowed down to six most potential varieties with highest resistance to bruchids. The present study is intended to manage pest control in post-harvest storage condition using easily available natural and eco-friendly treatment materials against the much-used chemical pest control materials. We have instinctively chosen eight treatment materials that are not used before except one in any earlier but similar studies of pest control management on other grains. Apart from direct natural sources of these treatment materials, we have used two ethnomedicinal dilution and evaluated their management efficacy as well.Result: The study highlights a new promising eco-friendly approach for bruchid management either through the ‘Homeo-Bruchid Interaction’ or through the ‘Easily Available Homemade Remedies.’ Our results are based on the crude extracts. In few specific situations, we have tried to give possible molecular level interactions that provide the bruchid resistance. However, further investigation is deemed necessary to properly assess the quality components of treating seed as well as identifying particular properties that are responsible for bruchid resistance and to confirm the level of human safety based on their bioactivity before commercialization.