Breeding Food Legumes for Resistance to Storage Insect Pests: Potential and Limitations

Acceptance and utilization efficiency of a purple durum wheat genotype by Sitophilus granarius (L.)

The granary weevil (Sitophilus granarius L.) is a major primary pest of stored cereals throughout the world. Among the major classes of plant secondary metabolites, flavonoids can affect insect feeding behaviour and their growth rate. In this study, the susceptibility of an anthocyanin-rich purple durum wheat genotype (T1303) to the granary weevil was evaluated in comparison with two yellow durum (Ofanto) and bread (Mec) wheat varieties. The feeding response and food utilisation efficiency by adult insects was also investigated by calculating nutritional indices in whole flour disk bioassays. Different levels of susceptibility to granary weevil emerged among genotypes tested. The mean food consumption by an insect, F1 progeny, and female parental offspring calculated for the T1303 genotype were significantly lower than those of yellow kernel wheat varieties. Moreover, T1303 genotype induced deterrence in the adult insects as demonstrated by the positive values of the food deterrence index. Besides, relative grow rate and efficiency conversion of ingested food indices were negative for T1303 and positive for both yellow wheat varieties indicating respectively a decrease and an increase of insect body weight during the bioassays. Finally, a higher mortality rate was recorded for insects fed on T1303 flour disks compared to disks obtained from yellow wheat varieties. These results provide evidence for the antifeedant and toxic effects of anthocyanins present in the T1303 pericarp against the granary weevil. Overall, this study contributes new insights into the mechanisms of host acceptance and food utilization by S. granarius and would be useful to identify antifeedant flavonoids as well as to develop varietal resistance-based strategies against this pest.

Mitigation of Acetamiprid Residue Disruption on Pea Seed Germination by Selenium Nanoparticles and Lentinans

The use of pesticides for pest control during the storage period of legume seeds is a common practice. This study evaluated the disruptive effects on pea seed germination and the repair effects of selenium nanoparticles (SeNPs) and lentinans (LNTs) This study examined the biomass, nutrient content, antioxidant indicators, plant hormones, phenolic compounds, and metabolites associated with the lignin biosynthesis pathway in pea sprouts. The application of acetamiprid resulted in a significant decrease in yield, amino-acid content, and phenolic compound content of pea sprouts, along with observed lignin deposition. Moreover, acetamiprid residue exerted a notable level of stress on pea sprouts, as evidenced by changes in antioxidant indicators and plant hormones. During pea seed germination, separate applications of 5 mg/L SeNPs or 20 mg/L LNTs partially alleviated the negative effects induced by acetamiprid. When used in combination, these treatments restored most of the aforementioned indicators to levels comparable to the control group. Correlation analysis suggested that the regulation of lignin content in pea sprouts may involve lignin monomer levels, reactive oxygen species (ROS) metabolism, and plant hormone signaling mediation. This study provides insight into the adverse impact of acetamiprid residues on pea sprout quality and highlights the reparative mechanism of SeNPs and LNTs, offering a quality assurance method for microgreens, particularly pea sprouts. Future studies can validate the findings of this study from the perspective of gene expression.

Investigation of insect population density, species composition and associated losses in chickpea seeds stored on farms in Ethiopia

This survey aimed to investigate the extent of insect infestations, associated losses, and insect species abundance in farm-stored chickpea seeds across five chickpea growing districts in Ethiopia. Despite being the largest producer, consumer, and exporter of chickpea in Africa, insect pest infestations have caused significant losses to Ethiopia's chickpea industry. Results showed that Callosobruchus chinensis (L.) was the most prevalent insect species, followed by Sitophilus oryzae (L.) and Tribolium confusum (J. du Val). The insect pests infested both local and improved chickpea varieties, and traditional containers and polypropylene bags were used for storage. The percentage of insect-damaged seed ranged from 4.61% to 14.48%, while the seed weight loss ranging from 1.13% to 4.55%. The range of seed germination percentages was from 65% to 88%, with a mean rate of 71%. These losses significantly affect the market value of the crop as grain and its use as seed, affecting farmers' income and food security. Therefore, it is crucial to develop effective solutions to prevent the loss of farm-stored chickpea in Ethiopia.

Insecticidal and Repellent Effects of the Essential Oils Extract from Zanthoxylum myriacanthum against Three Storage Pests

The co-storage of two or more Chinese herbal medicines can effectively prevent the herbs from the damage by pests. Thus, it is important to protect herbs and crops to study Chinese herbal medicines and their medicinal components against storage pests. This study aimed to assess the insecticidal activities and repellent effect of essential oils (EOs) extracted from fruits at different periods from Zanthoxylum myriacanthum Wall. ex Hook. f. (1 h, 2 h, 3-5 h and 5-7 h), and their major compounds against three kinds of pests (Tribolium castaneum, Lasioderma serricorne, and Liposcelis bostrychophila). The results of gas chromatography-mass spectrometer analysis revealed homomyrtenol (22.56 %, 28.01 %, 28.48 % and 28.41 %, respectively) and p-cymene (30.58 %, 13.95 %, 24.97 % and 6.85 %, respectively) were the common major compounds of the EOs at 1 h, 2 h, 3-5 h, and 5-7 h. m-Cymene contents in EOs of fruits, 1 h, 2 h and 3-5 h were 3.85 %, 0.95 %, 6.71 %, and 6.15 %, respectively. According to Principal component analysis (PCA), the composition of fruits' EO was significantly different from other EOs due to the different collection times. The bio-assays showed that EOs and major compounds were toxic to all three pests, but the fumigation effect on L. bostrychophila was not noticeable. EOs extracted at different times had a repellent effect on the three pests at the highest concentration (78.63 nL/cm2 ), but the attractive effects of the EOs of 3-5 h, 5-7 h, and p-cymene were observed at the low concentrations (3.15, 0.63 and 0.13 nL/cm2 ). Our results suggest that Z. myriacanthum have the potential to be developed as biological insecticides.

Advances in disease and pest resistance in faba bean

Faba bean (Vicia faba) is a grain legume crop widely cultivated in temperate areas for food and feed. Its productivity can be constrained by numerous diseases and pests that can be managed by a number of strategies, complemented with the deployment of resistant cultivars in an integrated manner. Few sources of resistance are available to some of them, although their phenotypic expression is usually insufficiently described, and their genetic basis is largely unknown. A few DNA markers have been developed for resistance to rust, ascochyta blight, and broomrape, but not yet for other diseases or pests. Still, germplasm screenings are allowing the identification of resistances that are being accumulated by classical breeding, succeeding in the development of cultivars with moderate levels of resistance. The adoption of novel phenotyping approaches and the unprecedented development of genomic resources along with speed breeding tools are speeding up resistance characterization and effective use in faba bean breeding.

Chemical Composition and Evaluation of Antifungal and Insecticidal Activities of Essential Oils Extracted from Jambosa caryophyllus (Thunb.) Nied: Clove Buds

Jambosa caryophyllus has been used in traditional phytotherapy as a treatment against infections. In the present work, essential oils extracted from clove buds (Jambosa caryophyllus ) (EO-JC) were investigated for their composition, antifungal, and insecticidal properties. Extraction of EO-JC was performed by use of hydrodistillation using a Clevenger-type apparatus, and the EOs were analyzed by gas chromatography coupled with mass spectrometry (GC-MS). Antifungal activity of EO-JC was evaluated by the use of solid-state diffusion (disc method) and microdilution to determine the minimum inhibitory concentration (MIC), against three strains of fungus, Aspergillus niger, Aspergillus flavus, and Fusarium oxysporum. Insecticidal activity of EO-JC against the cowpea weevil, Callosobruchus maculatus, was determined to assess utility of EO-JC to control this pest. Several exposures including inhalation and contact were used to determine lethality, as well as the repulsion test was conducted at concentrations of 4, 8, 16, and 32 μL EO-JC. Characterization of EO-JC by GC/MS revealed 34 compounds accounting for 99.98% of the mass of the extract. The predominant compound was eugenol (26.80%) followed by β-caryophyllene (16.03%) and eugenyl acetate (5.83%). The antifungal activity of EO-JC on solid media exhibited inhibitions in the range of 49% to 87%, and MIC was between 3.125 and 7.80 μg EO-JC/mL. Insecticidal activity, as determined by the use of the inhalation test, and expressed as the LD₅₀ and LD₉₅ after 96 hours of exposure was 2.32 and 21.92 μL/L air, respectively. In the contact test, a 96-hour exposure resulted in LD₅₀ and LD₉₅ of 5.51 and 11.05 μL/L of air, respectively. EO-JC exhibited insecticidal activity against fungi and pest chickpea weevil.

Endophytic Isaria javanica pf185 Persists after Spraying and Controls Myzus persicae (Hemiptera: Aphididae) and Colletotrichum acutatum (Glomerellales: Glomerellaceae) in Pepper

Simple Summary

The green peach aphid (Myzus persicae) and the phytopathogenic fungus Colletotrichum acutatum cause significant losses in a wide variety of crops. To efficiently protect their crops, farmers use chemical pesticides, but this kind of practice is not sustainable because of its negative effects on the environment. This study suggests an environmentally friendly method such as the use of the endophytic Isaria javanica pf185 in pepper plants. Suspension of the endophytic fungus (EF) was sprayed on plants under cage while those same leaves were sampled and assessed under laboratory conditions. The EF can both penetrate inside the leaf tissues and survive on the surface of the leaf after five weeks. The suspension showed an evident insecticidal efficiency against M. persicae and a lower one against C. acutatum. Therefore, its antifungal efficiency against C. acutatum was not correlated with weather patterns. Authors recommend I. javanica pf185 as a potential biocontrol agent against M. persicae and C. acutatum.

Abstract

This study endeavored to sustainably control aphids and anthracnose after spraying endophytic Isaria javanica pf185 under field conditions. Under two different tents; one batch of seedlings was sprayed with a 10⁷ conidia/mL I. javanica pf185 suspension; while another was sprayed with 0.05% Tween 80^® in distilled water. Six leaf discs from the top; middle; and bottom part of the plant canopy were weekly collected and placed on moistened filter paper in a Petri dish for insecticidal and antifungal bioassays against Myzus persicae and Colletotrichum acutatum. Differences were noticed from the 18th day after spraying with mortality (86.67 ± 0.57% versus 36.67 ± 0.64%) and leaf damage (13.45 ± 0.03% versus 41.18 ± 0.06%) on fungus-treated and controlled, respectively. The corrected insecticidal efficacy was 20.43, 39.82, 72.32, 66.43 and 70.04%, while the corrected fungicidal efficacy was 26.07, 38.01, 53.35, 29.08 and 41.81% during five successive weeks. A positive correlation was evident between insecticidal efficacy and relative humidity (r² = 0.620) and temperature (r² = 0.424), respectively. No correlation was found between antifungal activity and relative humidity (r² = 0.061) and temperature (r² = 0), respectively. The entomopathogenic fungus survived on leaf surface area and in tissues after spraying.

The resistance of the cowpea cv. BRS Xiquexique to infestation by cowpea weevil is related to the presence of toxic chitin-binding proteins

The cowpea weevil (Callosobruchus maculatus) is the main pest that attacks cowpea (Vigna unguiculata) seeds during storage, causing nutritional and economic losses in the cowpea crop. Thus, studies aiming to identify resistant cowpea cultivars have been developed. Chitin-binding proteins (CBP), such vicilins and chitinases, have been detected in seeds and related with the toxicity to insects. In this work, we investigated the presence of chitin-binding proteins in the partially resistant cowpea cv. BRS Xiquexique and evaluated their toxicity towards cowpea weevil. The CBP fraction was isolated by chitin affinity chromatography. CBP fraction showed, through 15% SDS PAGE, protein bands with varying molecular masses, mainly below 55 kDa. Proteins present in CBP fraction were identified by Western blotting and mass spectrometry analysis, as vicilins and chitinases. CBP fraction, at 5%, was able to interfere with the development of cowpea weevil, decreasing larval mass and length. A CBV (chitin-binding vicilin) fraction isolated from CBP fraction was toxic, at 2.0%, to C. maculatus, decreasing larval mass and length in 64.3% and 33.23%, respectively. These results suggest that chitin binding proteins, such vicilins and chitinases, may be related to the resistance of cowpea cv. BRS Xiquexique to the infestation by C. maculatus.

Breeding potential of lablab [Lablab purpureus (L.) Sweet]: a review on characterization and bruchid studies towards improved production and utilization in Africa

Lablab (Lablab purpureus) [Lablab purpureus (L.) Sweet] is termed a lost, underutilized and neglected crop in Africa. Despite the multipurpose use, production, consumption and research are still limited. Wide genetic diversity of lablab germplasm exists in Africa. Diversity studies provide significant information for subsequent research programs and improvement. The advent of genotyping and sequencing technologies has enabled the identification of unique and agronomically important traits. Application of next-generation sequencing on lablab as a pioneer orphan crop is currently underway. This has enabled description of the whole genome, generation of reference genome and resequencing that provide information on variation within the entire genome. Information from these technological advances helps in identifying potential traits for biotic and abiotic stress for further breeding programs. Storage pests specifically bruchids (Callosobruchus spp.), are considered a major obstacle in lablab production. Screening of available genotypes for bruchid resistance and studies on the physical and biochemical factors that confer resistance in lablab is required. Applying advanced technologies provides precise and reliable identification of the novel markers responsible for bruchid resistance allowing for introgression of important genes to breeding programs. This review provides a detailed analysis on the characterization of lablab and the information on bruchid resistance vital for breeding farmer-preferred varieties that possess agronomically beneficial traits. Concerted efforts and research on this neglected crop will enhance its production, utilization and consumption.

Efficacy of bioactive compounds and their association with different cowpea cultivars against their major stored pest

BACKGROUND

Stored grain insects are controlled with fumigant insecticides which can select resistant insect populations and cause environmental and applicator contamination. Thus, resistant cultivars and chemical constituents of essential oils are an alternative to the almost exclusive use of these insecticides. The effects of the combination of cowpea cultivars Vigna unguiculata (L.) Walp. with chemical constituents of essential oils against Callosobruchus maculatus were determined. Four cowpea cultivars: BRS Tracuateua, BR 17 Gurgueia, Epace 10 and Sempre Verde (insect rearing) untreated were used in the experiments and combined with chemical constituents of essential oil: eugenol, geraniol and trans-anethole. The biological parameters observed were: total egg number and eggs per grain, egg viability (%), insects emerged and insects per grain, immature stage viability (%), instantaneous rate of growth (ri), insect dry weight (mg), grain weight loss (%) and egg-adult period.

RESULTS

When comparing all biological parameters, the cultivars BRS Tracuateua and BR 17 Gurgueia were harmful to C. maculatus. In the toxicity tests, the results showed that LC₃₀ and LC₅₀ of the chemical constituents ranged from 54.77 to 103.48 ppm and 60.99 to 125.18 ppm, respectively. In most of the biological parameters, LC₅₀ had adverse effects significantly higher than LC₃₀ and BR 17 Gurgueia treated were harmful to C. maculatus.

CONCLUSIONS

Overall, the findings showed that BR 17 Gurgueia combined with eugenol and geraniol more significantly affected the biological parameters of C. maculatus than when associated with trans-anethole, reducing egg number, insects emerged and egg viability. © 2020 Society of Chemical Industry.

Identification of quantitative trait loci (QTL) controlling resistance to pea weevil (Bruchus pisorum) in a high-density integrated DArTseq SNP-based genetic map of pea

Pea weevil (Bruchus pisorum) is a damaging insect pest affecting pea (Pisum sativum) production worldwide. No resistant cultivars are available, although some levels of incomplete resistance have been identified in Pisum germplasm. To decipher the genetic control underlying the resistance previously identify in P. sativum ssp. syriacum, a recombinant inbred line (RIL F8:9) population was developed. The RIL was genotyped through Diversity Arrays Technology PL's DArTseq platform and screened under field conditions for weevil seed infestation and larval development along 5 environments. A newly integrated genetic linkage map was generated with a subset of 6,540 markers, assembled into seven linkage groups, equivalent to the number of haploid pea chromosomes. An accumulated distance of 2,503 cM was covered with an average density of 2.61 markers cM-1. The linkage map allowed the identification of three QTLs associated to reduced seed infestation along LGs I, II and IV. In addition, a QTL for reduced larval development was also identified in LGIV. Expression of these QTLs varied with the environment, being particularly interesting QTL BpSI.III that was detected in most of the environments studied. This high-saturated pea genetic map has also allowed the identification of seven potential candidate genes co-located with QTLs for marker-assisted selection, providing an opportunity for breeders to generate effective and sustainable strategies for weevil control.

Flower and Pod Source Influence on Pea Weevil (Bruchus pisorum) Oviposition Capacity and Preference

Bruchus pisorum is an insect pest causing major damage to pea seeds worldwide. Control is difficult and limited resistance is available. In this work we studied the effects of pollen and pod source on insect fecundity and oviposition by comparing resistant and susceptible Pisum spp. accessions and non-host (Lathyrus sativus and Vicia faba) species. A first no-choice assay revealed that the source of flower offered to adults for feeding might retard oviposition (the case of V. faba), reduce fertility (Pisum sativum ssp. syriacum, P. fulvum, and V. faba) or increase adult mortality (V. faba and P. sativum ssp. syriacum). A second no-choice assay with all adults fed with pollen of the same pea cultivar showed significant effect of the source of pods offered. Oviposition was reduced on pods of some resistant Pisum accessions, but particularly low on pods of the non-hosts, being retarded if ever happening and coupled with high mortality of adults. This was confirmed in a third experiment consisting on dual-choice assays showing reduced egg laying in V. faba, L. sativus, P. fulvum, and P. sativum ssp. syriacum compared to the commercial variety pea used as a control (Messire).

Biotic and Abiotic Constraints in Mungbean Production-Progress in Genetic Improvement

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.

The bean α-amylase inhibitor αAI-1 in genetically modified chickpea seeds does not harm parasitoid wasps

BACKGROUND

Legumes have been genetically engineered to express α-amylase inhibitor 1 (αAI-1) from common bean in their seeds. Whereas the genetically modified (GM) seeds are immune to multiple bruchid pest species, the cosmopolitan bruchid Acanthoscelides obtectus is tolerant to αAI-1 and their larvae develop normally inside the seeds. Hymenopteran bruchid parasitoids, the most important natural enemies of bruchids, might thus be exposed to αAI-1 when attacking A. obtectus larvae developing inside GM seeds. Exposure might reduce parasitoid fitness, resulting in a decline in the natural control of A. obtectus, and thus promote the spread of this pest. We investigated the impact of the presence of αAI-1 in legume seeds on parasitoid fitness in tritrophic experiments with αAI-1 GM or non-GM chickpea seeds, A. obtectus, and three parasitoid species. Additionally, we investigated the exposure of parasitoids to αAI-1 using a fourth, highly sensitive parasitoid species.

RESULTS

Parasitoid fitness was not affected when A. obtectus was used in GM chickpea seeds as hosts, and this lack of effects was probably attributable to the fact that exposure of the parasitoids to αAI-1 was negligible.

CONCLUSION

We conclude that the release of GM chickpeas containing αAI-1 should not harm this important group of non-target insects. © 2018 Society of Chemical Industry.

Identification of Novel Sources of Resistance to Seed Weevils (Bruchus spp.) in a Faba Bean Germplasm Collection

Seed weevils (Bruchus spp.) are major pests of faba bean, causing yield losses, and affecting marketability. Our objective was to identify stable sources of resistance to seed weevil attacks, determine the climatic factors that most influenced its incidence and its relationship with some phenological and agronomic traits. The accessions "BOBICK ROD115," "CÔTE D'OR," "221516," and "NOVA GRADISKA" showed increased resistance to penetration and development of larvae. Other accessions such as "QUASAR," "109.669," and "223303" exhibited resistance to larval development. The results of this work suggest the presence of different defense mechanisms to seed weevils in faba bean, which in the future could be introgressed in elite cultivars to create resistant varieties and contribute to more sustainable agriculture with less need for pesticides. The temperature, rainfall, and humidity seemed to be the climatic factors most influencing faba bean seed weevil attack while the precocity and the small weight of the seeds were correlated with lower infestation rates in the different experiments.

Faba Bean Cultivation - Revealing Novel Managing Practices for More Sustainable and Competitive European Cropping Systems

Faba beans are highly nutritious because of their high protein content: they are a good source of mineral nutrients, vitamins, and numerous bioactive compounds. Equally important is the contribution of faba bean in maintaining the sustainability of agricultural systems, as it is highly efficient in the symbiotic fixation of atmospheric nitrogen. This article provides an overview of factors influencing faba bean yield and quality, and addresses the main biotic and abiotic constraints. It also reviews the factors relating to the availability of genetic material and the agronomic features of faba bean production that contribute to high yield and the improvement of European cropping systems. Emphasis is to the importance of using new high-yielding cultivars that are characterized by a high protein content, low antinutritional compound content, and resistance to biotic and abiotic stresses. New cultivars should combine several of these characteristics if an increased and more stable production of faba bean in specific agroecological zones is to be achieved. Considering that climate change is also gradually affecting many European regions, it is imperative to breed elite cultivars that feature a higher abiotic-biotic stress resistance and nutritional value than currently used cultivars. Improved agronomical practices for faba bean crops, such as crop establishment and plant density, fertilization and irrigation regime, weed, pest and disease management, harvesting time, and harvesting practices are also addressed, since they play a crucial role in both the production and quality of faba bean.

Bruchid egg induced transcript dynamics in developing seeds of black gram (Vigna mungo)

Black gram (Vigna mungo) seeds are a rich source of digestible proteins, however, during storage these seeds are severely damaged by bruchids (Callosobruchus spp.), reducing seed quality and yield losses. Most of the cultivated genotypes of black gram are susceptible to bruchids, however, few tolerant genotypes have also been identified but the mechanism of tolerance is poorly understood. We employed Suppression Subtractive Hybridization (SSH) to identify specifically, but rarely expressed bruchid egg induced genes in black gram. In this study, Suppression Subtractive Hybridization (SSH) library was constructed to study the genes involved in defense response in black gram against bruchid infestation. An EST library of 277 clones was obtained for further analyses. Based on CAP3 assembly, 134 unigenes were computationally annotated using Blast2GOPRO software. In all, 20 defense related genes were subject to quantitative PCR analysis (qPCR) out of which 12 genes showed up-regulation in developing seeds of the pods oviposited by bruchids. Few major defense genes like defensin, pathogenesis related protein (PR), lipoxygenase (LOX) showed high expression levels in the oviposited population when compared with the non-oviposited plants. This is the first report on defense related gene transcript dynamics during the bruchid-black gram interaction using SSH library. This library would be useful to clone defense related gene(s) such as defensin as represented in our library for crop improvement.

Mechanism of Resistance in Mungbean [Vigna radiata (L.) R. Wilczek var. radiata] to bruchids, Callosobruchus spp. (Coleoptera: Bruchidae)

Mungbean [Vigna radiata (L.) R. Wilczek var. radiata] is an important pulse crop in Asia, and is consumed as dry seeds and as bean sprouts. It is an excellent source of digestible protein. Bruchids [Callosobruchus chinensis (L.) and Callosobruchus maculatus (F.)] are the important pests of mungbean and cause damage in the field and in storage. Bruchid infestation reduces the nutritional and market value of the grain and renders seeds unfit for human consumption, agricultural and commercial uses. These pests are controlled mainly by fumigation with highly toxic chemicals such as carbon disulfide, phosphene, and methyl bromide, or by dusting with several other insecticides, which leave residues on the grain, thus, threatening food safety. Some plant-based extracts have been found useful in controlling bruchids, but are not fully successful due to their short-term activity, rapid degradability, and potentially negative effect on seed germination. Although some wild sources of bruchid resistance in mungbean have been reported, which have been used to develop bruchid- resistant lines, undesirable genetic linkages threaten the proper exploitation of genetic diversity from wild germplasm into commercial cultivars. Further, biotype variation in bruchids has rendered some mungbean lines susceptible that otherwise would have been resistant to the pest. Host plant resistance is a cost-effective and a safe alternative to control bruchids in mungbean and is associated with morphological, biochemical, and molecular traits. These traits affect insect growth and development, thereby, reduce the yield losses by the pests. Understanding the defense mechanisms against insect pests could be utilized in exploiting these traits in crop breeding. This review discusses different traits in mungbean involved in defense against bruchids and their utility in pest management. We also highlight the breeding constraints for developing bruchid-resistant mungbean and how can these constraints be minimized. We further highlight the importance of supporting conventional breeding techniques by molecular techniques such as molecular markers linked to bruchid resistance.

Transcriptomic and Proteomic Research To Explore Bruchid-Resistant Genes in Mungbean Isogenic Lines

Mungbean (Vigna radiata (L.) Wilczek) is an important rotation legume crop for human nutrition in Asia. Bruchids (Callosobruchus spp.) currently cause heavy damage as pests of grain legumes during storage. We used omics-related technologies to study the mechanisms of bruchid resistance in seeds of the nearly isogenic lines VC1973A (bruchid-susceptible) and VC6089A (bruchid-resistant). A total of 399 differentially expressed genes (DEGs) were identified between the two lines by transcriptome sequencing. Among these DEGs, 251 exhibited high expression levels and 148 expressed low expression levels in seeds of VC6089A. Forty-five differential proteins (DPs) were identified by isobaric tags for relative and absolute quantification (iTRAQ); 21 DPs had higher abundances in VC6089A, and 24 DPs had higher abundances in VC1973A. According to transcriptome and proteome data, only three DEGs/DPs, including resistant-specific protein (g39185), gag/pol polyprotein (g34458), and aspartic proteinase (g5551), were identified and located on chromosomes 5, 1, and 7, respectively. Both g39185 and g34458 genes encode a protein containing a BURP domain. In previous research on bruchid molecular markers, the g39185 gene located close to the molecular markers of major bruchid-resistant locus may be a bruchid-resistant gene.

Identification of single nucleotide polymorphism markers associated with resistance to bruchids (Callosobruchus spp.) in wild mungbean (Vigna radiata var. sublobata) and cultivated V. radiata through genotyping by sequencing and quantitative trait locus analysis

BACKGROUND

Bruchid beetles are an important storage pest of grain legumes. Callosobruchus sp. infect mungbean (Vigna radiata) at low levels in the field, multiply during grain storage and can destroy seed stocks in a few months. Resistance against bruchid beetles has been found in wild mungbean V. radiata var. sublobata TC1966 and in cultivated mungbean line V2802.

RESULTS

Bruchid resistance data were obtained from recombinant inbred line populations TC1966 (V. radiata var. sublobata) × NM92 (F12) and V2802 (V. radiata) × NM94 (F7). More than 6,000 single nucleotide polymorphic markers were generated through genotyping by sequencing (GBS) for each of these populations and were used to map bruchid resistance genes. One highly significant quantitative trait locus (QTL) associated with bruchid resistance was mapped to chromosome 5 on genetic maps of both populations, suggesting that TC1966 and V2802 contain the same resistance locus. Co-segregation of all markers associated with resistance indicated the presence of only one major resistance QTL on chromosome 5, while QTL analysis based on physical map positions of the markers suggested the presence of multiple QTLs on different chromosomes. The diagnostic capacity of the identified molecular markers located in the QTL to correctly predict resistance was up to 100 %.

CONCLUSIONS

Molecular markers tightly linked to bruchid resistance loci of two different mungbean resistance sources were developed and validated. These markers are highly useful for developing resistant lines.

Resistance of αAI-1 transgenic chickpea (Cicer arietinum) and cowpea (Vigna unguiculata) dry grains to bruchid beetles (Coleoptera: Chrysomelidae)

Dry grain legume seeds possessing αAI-1, an α-amylase inhibitor from common bean (Phaseolus vulgaris), under the control of a cotyledon-specific promoter have been shown to be highly resistant to several important bruchid pest species. One transgenic chickpea and four cowpea lines expressing αAI-1, their respective controls, as well as nine conventional chickpea cultivars were assessed for their resistance to the bruchids Acanthoscelides obtectus (Say), Callosobruchus chinensis L. and Callosobruchus maculatus F. All transgenic lines were highly resistant to both Callosobruchus species. A. obtectus, known to be tolerant to αAI-1, was able to develop in all transgenic lines. While the cotyledons of all non-transgenic cultivars were highly susceptible to all bruchids, C. chinensis and C. maculatus larvae suffered from significantly increased mortality rates inside transgenic seeds. The main factor responsible for the partial resistance in the non-transgenic cultivars was deduced to reside in the seed coat. The αAI-1 present in seeds of transgenic chickpea and cowpea lines significantly increases their resistance to two important bruchid pest species (C. chinensis and C. maculatus) essentially to immunity. To control αAI-1 tolerant bruchid species such as A. obtectus and to avoid the development of resistance to αAI-1, varieties carrying this transgene should be protected with additional control measures.