QTL mapping and identification of genes associated with the resistance to Acanthoscelides obtectus in cultivated common bean using a high-density genetic linkage map.

BACKGROUND: Common bean (Phaseolus vulgaris L.) is an important agricultural product with large nutritional value, and the insect pest Acanthoscelides obtectus (Say) seriously affects its product quality and commodity quality during storage. Few researches on genes of bruchid resistance have investigated in common bean cultivars. RESULTS: In this study, a bruchid-resistant cultivar black kidney bean and a highly susceptible accession Longyundou3 from different gene banks were crossed to construct a recombinant inbred line population. The genetic analysis indicated a quantitative inheritance of the bruchid resistance trait controlled by polygenes. A high-density genetic map of a total map distance of 1283.68 cM with an average interval of 0.61 cM between each marker was constructed using an F6 population of 157 recombinant inbred lines. The map has 3106 bin markers, containing 2,234,769 SNPs. Using the high-density genetic map, a new quantitative trait locus for the resistance to Acanthoscelides obtectus was identified on chromosome 6. New molecular markers based on the candidate region were developed, and this locus was further delimited to an interval of 122.3 kb between SSR markers I6-4 and I6-16 using an F2 population. This region comprised five genes. Phvul.006G003700, which encodes a bifunctional inhibitor, may be a potential candidate gene for bruchid resistance. Sequencing analysis of candidate gene identified a 5 bp insertion-deletion in promoter of gene Phvul.006G003700 between two parents. Expression analysis of candidate gene revealed that the expression level of Phvul.006G003700 in bruchid-resistant parent was markedly higher than that in bruchid-susceptible parent both in dry seeds and leaves. CONCLUSIONS: A high-density genetic linkage map was constructed utilizing whole-genome resequencing and one new QTL for bruchid resistance was identified on chromosome 6 in common bean cultivar. Phvul.006G003700 (encoding a bifunctional inhibitor) may be a potential candidate gene. These results may form the basis for further research to reveal the bruchid resistance molecular mechanism of common bean.

Bruchid beetle ovipositioning mediated defense responses in black gram pods.

BACKGROUND: Black gram [Vigna mungo (L)] seeds are a rich source of digestible protein and dietary fibre, both for human and animal consumption. However, the quality and quantity of the Vigna seeds are severely affected by bruchid beetles during storage. Therefore, analyses of the expression of the bruchid induced transcript dynamics in black gram pods would be helpful to understand the underlying defense mechanism against bruchid oviposition. RESULTS: We used the RNAseq approach to survey the changes in transcript profile in the developing seeds of a moderately resistant cultivar IC-8219 against bruchid oviposition using a susceptible cultivar T-9 as a control. A total of 96,084,600 and 99,532,488 clean reads were generated from eight (4 each) samples of IC-8219 and T-9 cultivar, respectively. Based on the BLASTX search against the NR database, 32,584 CDSs were generated of which 31,817 CDSs were significantly similar to Vigna radiata, a close relative of Vigna mungo. The IC-8219 cultivar had 630 significantly differentially expressed genes (DEGs) of which 304 and 326 genes up and down-regulated, respectively. However, in the T-9 cultivar, only 168 DEGs were identified of which 142 and 26 genes up and down-regulated, respectively. The expression analyses of 10 DEGs by qPCR confirmed the accuracy of the RNA-Seq data. Gene Ontology and KEGG pathway analyses helped us to better understand the role of these DEGs in oviposition mediated defense response of black gram. In both the cultivars, the most significant transcriptomic changes in response to the oviposition were related to the induction of defense response genes, transcription factors, secondary metabolites, enzyme inhibitors, and signal transduction pathways. It appears that the bruchid ovipositioning mediated defense response in black gram is induced by SA signaling pathways and defense genes such as defensin, genes for secondary metabolites, and enzyme inhibitors could be potential candidates for resistance to bruchids. CONCLUSION: We generated a transcript profile of immature black gram pods upon bruchid ovipositioning by de novo assembly and studied the underlying defense mechanism of a moderately resistant cultivar.

Development of a Phytochemical-Based Lure for the Dried Bean Beetle Acanthoscelides obtectus Say (Coleoptera: Chrysomelidae).

The dried bean beetle, Acanthoscelides obtectus, is an economically important, worldwide pest of legume crops including dry beans, Phaseolus vulgaris. Assessment of A. obtectus infestation levels in pre-harvest field crops and post-harvest granaries is difficult to achieve because there is no effective monitoring tool for early detection so that interventions can be deployed as needed. Because A. obtectus is a generic pollen and nectar feeder, we adopted an electrophysiological (EAG) screening approach, using the antennae of female A. obtectus to identify physiologically active, volatile phytochemicals, which could then be investigated for their attractiveness to A. obtectus in laboratory behavioral assays and preliminary field tests. Of the 27 compounds tested in EAG screening, 5 compounds, i.e., methyl anthranilate, methyl eugenol, benzyl alcohol, (RS)-lavandulol, and 2-phenylethanol, elicited stronger EAG responses than the standard (1-phenylethanol). In 4-arm olfactometer bioassays, female A. obtectus preferred the olfactometer arm containing the odor of either methyl anthranilate or benzyl alcohol compared to the solvent control. In preliminary field tests using these 2 compounds as a binary mixture, at least 5 times as many beetles were caught on baited traps compared to non-baited traps. The field data also suggested that benzyl alcohol was primarily responsible for the field activity of the blend. We hypothesize that the attraction of A. obtectus to the combined benzyl alcohol/methyl anthranilate and the single benzyl alcohol baits is connected to the species` nectar- and pollen-feeding behaviour and not to its intraspecific communication. To our knowledge, this is the first evidence that A. obtectus behavior in the field can be modified by the deployment of plant-derived semiochemicals.

Efficacy of Ocimum tenuiflorum essential oil as grain protectant against coleopteran beetle, infesting stored pulses.

In the present investigation, essential oil (EO) of Ocimum tenuiflorum and its principal constituent (eugenol) was evaluated for its toxicity and mode of action against Callosobruchus maculatus. Furthermore, fumigant toxicity and germination studies on the application of O. tenuiflorum EO and eugenol against C. maculatus on different pulses was also studied. Fumigant activity studies revealed that EO toxicity was significantly (p < 0.05) influenced by concentration and exposure time. In fumigant toxicity assay without food, O. tenuiflorum EO and eugenol showed LC50 value of 278.6 and 256.5 µL/L air, respectively, at one hour exposure. Further, O. tenuiflorum EO displayed fumigant toxicity via inhibiting acetylcholinesterase activity. Pulses treated with O. tenuiflorum EO showed 70% of C. maculatus mortality at 250 µL/L air concentration after 24 h. Furthermore, these treatments didn't affect the seed viability of the pulses tested. Hence, the application of O. tenuiflorum EO has potential scope as a botanical insecticide.

A second VrPGIP1 allele is associated with bruchid resistance (Callosobruchus spp.) in wild mungbean (Vigna radiata var. sublobata) accession ACC41.

Two bruchid species, azuki bean weevil (Callosobruchus chinensis L.) and cowpea weevil (Callosobruchus maculatus F.), are the most important insect pests of mungbean [Vigna radiata (L.) Wilczek] after harvest. Improving bruchid resistance is a major goal for mungbean breeders. Bruchid resistance in mungbean is controlled by a single major locus, Br. The tightly linked VrPGIP1 and VrPGIP2, which encode polygalacturonase-inhibiting proteins (PGIPs), are the candidate genes at the Br locus associated with bruchid resistance. One VrPGIP1 resistance allele and two VrPGIP2 resistance alleles have been identified. In this study, we fine-mapped the bruchid-resistance genes in wild mungbean (V. radiata var. sublobata) accession ACC41 using the F2 population (574 individuals) derived from the 'Kamphaeng Saen 2' (susceptible) × ACC41 (resistant) cross. A QTL analysis indicated that the resistance to the azuki bean weevil and cowpea weevil in ACC41 is controlled by a major QTL (qBr5.1) and a minor QTL (qBr5.2), which are only 0.3 cM apart. qBr5.1 and qBr5.2 accounted for about 82% and 2% of the resistance variation in the F2 population, respectively. qBr5.1 was mapped to a 237.35-kb region on mungbean chromosome 5 containing eight annotated genes, including VrPGIP1 and VrPGIP2. An examination of the ACC41 VrPGIP1 and VrPGIP2 sequences revealed a new allele for VrPGIP1 (i.e., VrPGIP1-2). Compared with the wild-type sequence, VrPGIP1-2 has five SNPs, of which four cause amino acid changes (residues 125, 129, 188, and 336). A protein sequence analysis indicated that residues 125 and 129 in VrPGIP1-2 are in a ß-sheet B1 region, whereas residues 188 and 336 are in a C10-helix region and at the end of the C-terminal region, respectively. Because the ß-sheet B1 region is important for interactions with polygalacturonase (PG), residues 125 and 129 in VrPGIP1-2 likely contribute to bruchid resistance by inhibiting PG. Our results imply that VrPGIP1-2 is associated with the bruchid resistance of wild mungbean accession ACC41. This new resistance allele may be useful for breeding mungbean varieties exhibiting durable bruchid resistance.

Sulfated Purine Alkaloid Glycosides from the Pupal Case Built by the Bruchid Beetle Bruchidius dorsalis Inside the Seed of Gleditsia japonica.

Three new sulfated isoguanine alkaloid glycosides, designated as saikachinoside A monosulfate (1), saikachinoside A disulfate (2), and locustoside B disulfate (3), have been isolated from the pupal case of the wild bruchid seed beetle Bruchidius dorsalis (Chrysomelidae, Bruchinae) infesting the seed of Gleditsia japonica Miq. (Fabaceae). Their structures were determined by spectroscopic methods and the inhibitory activity of 2 and 3 against acid phosphatase was evaluated.

Life history traits influence the strength of distance- and density-dependence at different life stages of two Amazonian palms.

Background and Aims: Natural enemies are known to be important in regulating plant populations and contributing to species coexistence (Janzen-Connell effects). The strength of Janzen-Connell effects (both distance- and density-effects) varies across species, but the life history traits that may mediate such a variation are not well understood. This study examined Janzen-Connell effects across the life stages (seed through adult stages) of two sympatric palm species with distinct phenologies and shade tolerances, two traits that may mediate the strength and timing of Janzen-Connell effects. Methods: Populations of two common palm species, Attalea phalerata and Astrocaryum murumuru , were studied in Manu National Park, Peru. Seed predation experiments were conducted to assess Janzen-Connell effects at the seed stage. In the post-seed stages, spatial point pattern analyses of the distributions of individuals and biomass were used to infer the strength of distance- and density-effects. Key Results: Seed predation was both negative distance- and density-dependent consistent with the Janzen-Connell effects. However, only seedling recruitment for asynchronously fruiting Attalea phalerata was depressed near adults while recruitment remained high for synchronously fruiting Astrocaryum murumuru , consistent with weak distance-effects. Negative density-effects were strong in the early stages for shade-intolerant Attalea phalerata but weak or absent in shade-tolerant Astrocaryum murumuru. Conclusions: Distance- and density-effects varied among the life stages of the two palm species in a manner that corresponded to their contrasting phenology and shade tolerance. Generalizing such connections across many species would provide a route to understanding how trait-mediated Janzen-Connell effects scale up to whole communities of species.

Chemical Composition of the Essential Oil of Nigeria Grown Hoslundia opposita Vahl (Lamiaceae) Dried Leaves and Its Bioactivity against Cowpea Seed Bruchid.

Due to several ecological and human hazards of synthetic pesticides in postharvest crop protection, there is the need to search for eco-friendly alternatives. In this study, chemical composition and insecticidal activities of essential oil (EO) obtained from Hoslundia opposita dried leaves were evaluated against cowpea seed bruchid. Eight constituents, predominated by oxygenated monoterpenes (78.86%), were identified using Gas Chromatography (GC)/MS. The constituents were 1,8-cineole (1; 61.15%), followed by α-terpineol (2; 16.81%), ß-phellandrene (3; 13.24%), ß-farnesene (4; 3.55%), α-pinene (5; 1.89%), Germacrene D (6; 1.83%), cis-sabinene hydrate (7; 0.90%) and caryophyllene (8; 0.63%). In fumigation bioassay, at 6 h after exposure (HAE), 0.78 ml EO/l air caused 35.33% mortality which was significantly lower than 60.90% and 63.6% observed at 3.15 and 6.25 ml/l air, respectively. Mortality reached 90.0% at 24 HAE regardless of the applied concentration. Lethal time for 50% of the bruchids (LT50 ) at concentration of 0.78 ml/l air (6.89 h) was higher than the LT50 at 3.15 and 6.25 ml/l air (4.72 and 4.44 h, respectively). H. opposita EO reduced Callosobruchus maculatus oviposition, while progeny emergence observed in EO-treated seeds (2.42 - 25.73) was significantly (P < 0.05) lower than 51.56 observed in control. The results confirm H. opposita EO's potentials for control of cowpea bruchids.

Insect midgut carboxypeptidases with emphasis on S10 hemipteran and M14 lepidopteran carboxypeptidases.

We compared the whole complement of midgut carboxypeptidases from 10 insects pertaining to five orders based on transcriptomes obtained by deep sequencing and biochemical data. Most of the carboxypeptidases were metallocarboxypeptidases from family M14, with carboxypeptidase A (CPA) predominating over carboxypeptidase B (CPB). They were found in all of the insects studied except for the hemipterans and a bruchid beetle. M14 carboxypeptidases were expressed only in the midgut of Spodoptera frugiperda (Lepidoptera). The most expressed CPA from this insect (SfCPA) was cloned, sequenced and expressed as a recombinant enzyme. This enzyme was used to generate antibodies used to demonstrate that SfCPA is secreted by an exocytic route. Serine carboxypeptidases from family S10 were found in all of the insects studied here. In S. frugiperda, they are expressed in all tissues besides the midgut, in accordance with their presumed lysosomal role. In the hemipteran Dysdercus peruvianus, S10 carboxypeptidases are expressed only in midgut, suggesting that they are digestive enzymes. This was confirmed by enzyme assays of midgut contents. Furthermore, the substrate specificity of D. peruvianus S10 carboxypeptidases are predicted to be one CPC (preferring hydrophobic residues) and one CPD (preferring basic residues), thus able to hydrolyse the peptides formed by their digestive cathepsin D and cathepsin L, respectively. The role of S10 carboxypeptidases in bruchid beetles are suggested to be the same as in hemipterans.

Efficacy and insecticidal properties of some essential oils against Caryedon serratus (Oliver)-a storage pest of groundnut.

During storage groundnut is attacked by number of stored grain pest and management of these insect pests particularly bruchid beetle, Caryedon serratus (Oliver) is of prime importance as they directly damage the pod and kernels. Hence, some essential oils were tested for their insecticidal and fungicidal properties. Highest total bruchid mortality was recorded with the application of neem oil and pongamia oil at 10% (v/w) concentration and lowest in eucalyptus oil at 5% (v/w). Number of eggs laid was recorded 2.3 in neem oil 10% (v/w) which was lowest and significantly superior over untreated control and was at par with castor oil 10% (v/w) which recorded 2.5 eggs per 100 g of groundnut pods. There was no adult emergence in the groundnut pods treated with castor oil, eucalyptus oil, neem oil and pongamia oil at 10% (v/w) concentration. Groundnut pods treated with castor oil, eucalyptus oil, neem oil and pongamia oil at 10% (v/w) and neem oil at 5% (v/w) concentrations recorded no damage to pods and kernels and also zero per cent weight loss. These oils effectively influenced groundnut bruchid establishment and reduce damage besides reduction in aflatoxin contamination.

Mapping of quantitative trait locus reveals PsXI gene encoding xylanase inhibitor as the candidate gene for bruchid (Callosobruchus spp.) resistance in pea (Pisum sativum L.).

Pea (Pisum sativum L.) is an important legume crop for both food and feed. Bruchids (Callosobruchus spp.) are destructive insect pests of pea in the field and during storage. In this study, we identified a major quantitative trait locus (QTL) controlling seed resistance to C. chinensis (L.) and C. maculatus (Fab.) in field pea using F2 populations derived from a cross between PWY19 (resistant) and PHM22 (susceptible). QTL analysis in the two F2 populations grown in different environments consistently identified a single major QTL, qPsBr2.1, controlling the resistance to both bruchid species. qPsBr2.1 was mapped onto linkage group 2 between DNA markers 18339 and PSSR202109 and explained 50.91% to 70.94% of the variation in resistance, depending on the environment and bruchid species. Fine mapping narrowed down qPsBr2.1 to a genomic region of 1.07 Mb on chromosome 2 (chr2LG1). Seven annotated genes were found in this region, including Psat2g026280 (designated as PsXI), which encodes a xylanase inhibitor and was considered as a candidate gene for bruchid resistance. PCR amplification and sequence analysis of PsXI suggested the presence of an insertion of unknown length in an intron of PWY19, which causes variation in the open reading frame (ORF) of PsXI. Moreover, the subcellular localization of PsXI differed between PWY19 and PHM22. These results together suggested that PsXI encoding xylanase inhibitor is responsible for the bruchid resistance of the field pea PWY19.

A Gene Encoding Xylanase Inhibitor Is a Candidate Gene for Bruchid (Callosobruchus spp.) Resistance in Zombi Pea (Vigna vexillata (L.) A. Rich).

Two bruchid species, Callosobruchus maculatus and Callosobruchus chinensis, are the most significant stored insect pests of tropical legume crops. Previously, we identified a major QTL, qBr6.1, controlling seed resistance to these bruchids in the cultivated zombi pea (Vigna vexillata) accession 'TVNu 240'. In this study, we have narrowed down the qBr6.1 region and identified a candidate gene conferring this resistance. Fine mapping using F2 and F2:3 populations derived from a cross between TVNu 240 and TVNu 1623 (susceptible) revealed the existence of two tightly linked QTLs, designated qBr6.1-A and qBr6.1-B, within the qBr6.1. The QTLs qBr6.1-A and qBr6.1-B explained 37.46% and 10.63% of bruchid resistance variation, respectively. qBr6.1-A was mapped to a 28.24 kb region containing four genes, from which the gene VvTaXI encoding a xylanase inhibitor was selected as a candidate gene responsible for the resistance associated with the qBr6.1-A. Sequencing and sequence alignment of VvTaXI from TVNu 240 and TVNu 1623 revealed a 1-base-pair insertion/deletion and five single-nucleotide polymorphisms (SNPs) in the 5' UTR and 11 SNPs in the exon. Alignment of the VvTAXI protein sequences showed five amino acid changes between the TVNu 240 and TVNu 1623 sequences. Altogether, these results demonstrated that the VvTaXI encoding xylanase inhibitor is the candidate gene conferring bruchid resistance in the zombi pea accession TVNu 240. The gene VvTaXI will be useful for the molecular breeding of bruchid resistance in the zombi pea.

Optimizing Insecticide Application Timing for Broad Bean Weevil Control and Minimizing Crop Damage in Broad Bean (Vicia faba Linn.).

During the growing seasons of 2018 to 2020, a field experiment in broad bean (Vicia faba L.) was conducted at the Lithuanian Research Centre for Agriculture and Forestry. The objective of the study was to explore the effects of the timing of insecticide application on the abundance, damage, and control of the broad bean weevil (Bruchus rufimanus Boh.). The experiment included four spray regimes and an untreated control. Yellow water traps were utilized to monitor the broad bean weevil from germination to senescence. Results indicate that broad bean weevil infestation occurred in all study years, with the highest density of adults observed during the flowering stage. Damage to seeds ranged from 23% to 59.62%. The data suggest that B. rufimanus infestation can result in a 19.1% reduction in seed yield. However, spraying when the daily temperature exceeded the threshold for adult activity for 3 days and at the end of flowering produced a significant increase in yield of 13.3% and 6.6%, respectively. Additionally, the spray at the end of flowering reduced damaged seeds by 21.4-48%.

Evaluation of Insecticidal Potentials of Five Plant Extracts against the Stored Grain Pest, Callosobruchus maculatus (Coleoptera: Bruchidae).

Plant based insecticides are considered among the most economic and ecofriendly chemicals for the protection of plants and stored grains. The cowpea weevil (Callosbruchus maculatus) causes more than 90% damage to sored grains in three to six months. The current study investigates insecticidal potentials of five selected botanicals: Melia azedarach, Nicotiana rustica, Azadirachta indica, Nicotiana tabacum and Thuja orientalis. They are explored at six different concentrations (0.5, 1.0, 1.5, 2.0, 2.5 and 3.0%) against C. maculatus and compared to effects of distilled water which is used as a control. Toxicities of 3%(V/V) extracts of N. tabacum, N. rustica, A. indica and T. orientalis against C. maculatus were 100%, 86.11%, 80.56% and 72.22%, respectively. Maximum mortality was caused by N. tabacum and N. rustica (100%), followed by A. indica (82%), whereas minimum mortality was observed in T. orientalis (64%) at 2.5%. Several phytochemicals, alkaloids, saponins, diterphenes, phytosterol, flavonoids and phenols were identified in N. tabacum and N. rustica, while few were present in A. indica. Phytosterol was present in greatest abundance. Saponins were only detected in aqueous extracts of N. rustica and N. tabacum. Taken together, these results indicate the utility of N. tabacum, N. rustica and A. indica as potential botanicals to control pest beetle and cowpea weevil.

Tandemly duplicated genes encoding polygalacturonase inhibitors are associated with bruchid (Callosobruchus chinensis) resistance in moth bean (Vigna aconitifolia).

Bruchids are stored-grain insect pests responsible for serious seed loss in legume crops. A previous study using an F2 population (F2OA) derived from a cross between wild moth-bean (Vigna aconitifolia [Jacq.] Maréchal) accession TN67 (resistant) and cultivated moth-bean accession ICPMO056 (susceptible) revealed that resistance to the azuki bean weevil (Callosobruchus chinensis L.) in TN67 was regulated by a single gene located in the major quantitative trait locus-qVacBrc2.1. In this study, qVacBrc2.1 was finely mapped and candidate genes in this locus were identified using F2OA and another large F2 population (F2NB) derived from the cross mentioned previously. In contrast to the previous study, segregation analysis in the F2NB population revealed that resistance against this pest was controlled by two genes. Furthermore, the addition of novel markers to qVacBrc2.1 and reanalysis of the QTL in the F2OA population demonstrated that qVacBrc2.1 constituted two linked QTLs-qVacBrc2.1-A and qVacBrc2.1-B. The presence of qVacBrc2.1-B was verified using the population F2NB. Comparative genomics using three Vigna spp. strongly suggested the presence of two tandemly duplicated genes, VacPGIP1 and VacPGIP2, which encoded polygalacturonase inhibitors (polygalacturonase-inhibiting proteins) as the candidates for conferring resistance, but only VacPGIP1 could be successfully cloned and sequenced. The alignment of VacPGIP1 coding sequences of TN67 and ICPMO056 revealed eight single nucleotide polymorphisms, three of which altered the amino-acid sequence of the predicted domains of polygalacturonase inhibitors in ICPMO056. Overall, these findings indicate that VacPGIP1 and VacPGIP2 regulated C. chinensis resistance in TN67.

Insecticidal activities of long pepper (Piper retrofractum Vahl) fruit extracts against seed beetles (Callosobruchus maculatus Fabricius, Callosobruchus chinensis Linnaeus, and Sitophilus zeamais Motschulsky) and their effects on seed germination.

Bruchid beetles (Callosobruchus maculatus and Callosobruchus chinensis), and maize weevil (Sitophilus zeamais) are important insect pests during the postharvest period. Botanical insecticide is an alternative solution for controlling these insects, and long pepper (Piper retrofractum) has been reported as having insecticidal potential against general insect pests. Film seed coatings with various concentrations of hexane extracts were made for mung bean (Vigna radiata) and corn (Zea mays) seeds. Insecticidal activities of these treatments were assessed at before and after storage period of six months, and seed germination was also evaluated. The hexane extract was subjected to analysis of the bioactive components by using Gas Chromatography-Mass Spectrometry (GC-MS). Results revealed that the hexane extract presented extreme toxicity to both bruchid beetles higher compared to maize weevil at 24 h with LC50 values of 5.57-6.75 and 58.04 µg⋅cm-2, respectively. Bruchid beetles presented significant response to ethanol, acetone and hexane extracts, whereas maize weevil showed relatively low responsibility. Film seed coating with hexane extract at 1% and 3% concentrations with six-month storage presented high insecticidal activity against bruchid beetles by more than 88% mortality but had low kill rates against maize weevil. The coated mung bean seeds presented non-seed germination effect, whereas high effect was observed on coated corn. Isolation of bioactive components demonstrated that there were 74 compounds, where pentadecane was the main compound. Film seed coating technology for mung bean seed preservation by using 1% hexane extract from long pepper fruit presented to be an extremely effective method to control bruchid beetles without any seed germination effect. It could serve as one of the green insecticides of the future.

Construction of High-Density Genetic Map and Identification of a Bruchid Resistance Locus in Mung Bean (Vigna radiata L.).

Mung bean (Vigna radiata L.) is an economically important grain legume cultivated in Asian countries. High-density genetic linkage is a valuable and effective tool for mapping quantitative trait loci (QTL). In the current study, a high-resolution genetic map containing 4,180 single-nucleotide polymorphisms (SNPs) was assigned to 11 linkage groups (LGs) and spanning 1,751.39 cM in length was constructed for mung bean, and the average distance between adjacent markers was 0.42 cM. Bruchids (Callosobruchus spp.) cause significant damage to and loss of legume seeds. A locus for bruchid resistance was detected. The gene Vradi05g03810, encoding a probable resistance-specific protein, was found to be the most likely key candidate gene in mung beans. A 69-bp sequence deletion was identified in the coding region by comparing the cDNA sequences of bruchid-resistant and bruchid-susceptible lines. This SNP-based high-density linkage map is one of the first to be constructed across the mung bean genome. This map will not only facilitate the genetic mapping of genes or complex loci that control important agronomic traits but also offer a tool for promoting future genetics and comparative genomic studies in Vigna.

Two polygalacturonase-inhibiting proteins (VrPGIP) of Vigna radiata confer resistance to bruchids (Callosobruchus spp.).

Bruchids (Callosobruchus spp.) are destructive storage pests of mung beans (Vigna radiata). Bruchids infest mature seeds during storage and in the field causing heavy losses. Bruchid resistance in mung bean has been characterized as a dominant trait controlled by a single gene. Several independent mapping studies showed that the Br locus on chromosome 5 was a key quantitative trait loci (QTL) involved in bruchid resistance. Two polygalacturonase-inhibitor protein (PGIP) family genes, VrPGIP1 and VrPGIP2, located in the Br locus may be the primary genes responsible for bruchid resistance in mung bean but no experimental proof is available. We isolated the VrPGIP1 and VrPGIP2 genes from bruchid resistant mung bean cultivar V2802 and purified the proteins by prokaryotic expression. Both VrPGIP1 and VrPGIP2 had polygalacturonase inhibitor activity and both of the PGIP proteins conferred resistance to bruchids in an artificial seed test system. VrPGIPs can inhibit the enzyme activity of polygalacturonase present in males, females and fourth instar larvae of C. maculatus. These results demonstrated that VrPGIP1 and VrPGIP2 play a critical role in bruchid resistance probably through inhibiting polygalacturonase activity.

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.

Seed Predation on Oil-Polluted and Unpolluted Vachellia (Acacia) Trees in a Hyper-Arid Desert Ecosystem.

Acacia trees are keystone species in many arid environments, supporting high levels of plant and animal diversity. In Israel, the populations of Vachellia (formerly Acacia) tortilis (Forssk.) and V. raddiana (Savi) are declining at an alarming rate. Severe infestations by bruchid beetles (Coleoptera, Chrysomelidae) are among the major causes of seed mortality, but additional environmental stressors can reduce the defence level of the seeds, exacerbating their susceptibility to predators. In a hyper-arid desert ecosystem affected by two major oil spills (in 1975 and 2014), we quantified seed predation rates caused by insect granivores before and after the pods dropped to the ground. We recorded predation rates of up to 84% for both tree species, and higher predation rates at the ground level than in the canopy, suggesting that repeated infestations occur. These results reinforce the call to protect the populations of large ungulates such as gazelles, which kill the bruchids by feeding upon the pods, and promote seed germination and dispersion. We found no clear evidence of a negative effect of the oil spill on seed predation, indicating that oil pollution did not increase the vulnerability of the seeds to granivores even in trees affected by the recent oil spill.