Resistant Cowpea Research Articles

Biodiversity assessment and environmental risk analysis of the single line transgenic pod borer resistant cowpea.

The discussion surrounding biological diversity has reached a critical point with the introduction of Nigeria's first transgenic food crop, the pod borer-resistant (PBR) cowpea. Questions have been raised about the potential risks of the transgenic Maruca vitrata-resistant cowpea to human health and beneficial insects. Public apprehension, coupled with social activists' calling for the removal of this crop from the nation's food market, persists. However, there is a lack of data to counter the assertion that cultivating PBR cowpea may have adverse effects on biodiversity and the overall ecological system. This research, with its multifaceted objective of examining the environmental safety of PBR cowpea and assessing its impact on biodiversity compared to its non-transgenic counterpart, IT97KN, is of utmost importance in providing the necessary data to address these concerns. Seeds for both the transgenic PBR cowpea and its isoline were obtained from the Institute for Agricultural Research (IAR) Zaria before planting at various farm sites (Addae et al., 2020). Throughout the experiment, local cultural practices were strictly followed to cultivate both transgenic and non-transgenic cowpeas. Elaborate taxonomic keys were used to identify arthropods and other non-targeted organisms. Principal component analysis (PCA) was used to evaluate potential modifications in all ecological niches of the crops. The lmer function of the R package lme4 was used to analyze diversity indices, including Shannon, Pielou, and Simpson. The Bray-Curtis index was used to analyzed potential modifications in the dissimilarities of non-targeted organisms' communities. Examination of ecological species abundance per counting week (CW) revealed no disruption in the biological properties of non-targeted species due to the cultivation of transgenic PBR cowpea. Analysis of species evenness and diversity indices indicated no significant difference between the fields of transgenic PBR cowpea and its isoline. Principal component analysis results demonstrated that planting PBR cowpea did not create an imbalance in the distribution of ecological species. All species and families observed during this study were more abundant in transgenic PBR cowpea fields than in non-transgenic cowpea fields, suggesting that the transformation of cowpea does not negatively impact non-targeted organisms and their communities. Evolution dynamics of the species community between transgenic and non-transgenic cowpea fields showed a similar trend throughout the study period, with no significant divergence induced in the community structure because of PBR cowpea planting. This study concludes that planting transgenic PBR cowpea positively influences biodiversity and the environment.

Enhancing cowpea wilt resistance: insights from gene coexpression network analysis with exogenous melatonin treatment

BackgroundCowpea wilt is a harmful disease caused by Fusarium oxysporum, leading to substantial losses in cowpea production. Melatonin reportedly regulates plant immunity to pathogens; however the specific regulatory mechanism underlying the protective effect of melatonin pretreated of cowpea against Fusarium oxysporum remains known. Accordingly, the study sought to evaluate changes in the physiological and biochemical indices of cowpea following melatonin treated to facilitate Fusarium oxysporum resistance and elucidate the associated molecular mechanism using a weighted gene coexpression network.ResultsTreatment with 100 µM melatonin was effective in increasing cowpea resistance to Fusarium oxysporum. Glutathione peroxidase (GSH-PX), catalase (CAT), and salicylic acid (SA) levels were significantly upregulated, and hydrogen peroxide (H2O2) levels were significantly downregulated in melatonin treated samples in roots. Weighted gene coexpression network analysis of melatonin- and Fusarium oxysporum-treated samples identified six expression modules comprising 2266 genes; the number of genes per module ranged from 9 to 895. In particular, 17 redox genes and 32 transcription factors within the blue module formed a complex interconnected expression network. KEGG analysis revealed that the associated pathways were enriched in secondary metabolism, peroxisomes, phenylalanine metabolism, flavonoids, and flavonol biosynthesis. More specifically, genes involved in lignin synthesis, catalase, superoxide dismutase, and peroxidase were upregulated. Additionally, exogenous melatonin induced activation of transcription factors, such as WRKY and MYB.ConclusionsThe study elucidated changes in the expression of genes associated with the response of cowpea to Fusarium oxysporum under melatonin treated. Specifically, multiple defence mechanisms were initiated to improve cowpea resistance to Fusarium oxysporum.

Application of Molecular Markers for the Identification of Resistant Cowpea Varieties Against Fusarium Wilt in the Sudano-Sahalian Zone of Cameroon

Application of Molecular Markers for the Identification of Resistant Cowpea Varieties Against Fusarium Wilt in the Sudano-Sahalian Zone of Cameroon

Pyramiding aphid resistance genes into the elite cowpea variety, Zaayura, using marker-assisted backcrossing

The cowpea aphid (Aphis cracivora) is a cosmopolitan insect pest that causes economic damage on cowpea. Although the pest persists at all the growth stages of the crop, in West Africa, aphids are the only major insect pests that farmers regularly control at the vegetative stage. Thus, deploying aphid-resistant crop varieties can reduce farmers' expenditure on insecticide. The availability of different biotypes of the pest and reports of resistance breakdown necessitates pyramiding of sources of aphid resistance to develop a more robust genotype for durable resistance. Two aphid-resistance genes, sourced from SARC-1-57-2 and IT97K-556-6, were introgressed through gene pyramiding technique into a farmers’ preferred cowpea variety, Zaayura, using marker-assisted backcrossing. A simple sequence repeat (SSR) marker, CP 171F/172R, and an allele-specific single nucleotide polymorphism (SNP) marker, 1_0912, were used for foreground selection of the SARC-1-57-2 and IT97K-556-6 aphid resistance genes, respectively. A stepwise backcross approach was used to introgress the major aphid resistance QTL (QAc-vu7.1) from IT97K-556-6 into Zaayura using the marker 1_0912 coupled with intermittent screening under artificial aphid infestation. After the fourth backcross generation, three heterozygous BC4F1 of Zaayura/TT97K-556-6 were intercrossed to Zaayura Pali to develop intercross F1 (ICF1). Three true ICF1 hybrids allowed to self to produce ICF2. Five (5) out of 48 ICF2 plants which were genotyped with the two foreground markers had the two aphid resistance genes fixed in the double homozygous dominant state. For background selection, out of 192 allele-specific markers screened, only 47 polymorphic markers were identified and used for the background analysis of the pyramided lines. The recurrent parent genome recovery ranged from 72 to 93.8 %. ICF2_Zaa/556/SARC-P6 had the highest recurrent parent genome and the least heterozygosity among the five improved lines. The five pyramided lines showed superior resistance under artificial aphid infestation as compared to the two donor parents with damage scores ranging from 2.0 to 2.3. On the field, however, there were no significant differences between the pyramided lines and their recurrent parent for all the agronomic traits measured except for grain yield. The pyramided lines do not only stand the chance of being released as new varieties but are also valuable genetic resources for other breeding programs that seek to improve cowpea for aphid resistance.

Host status of melon, carrot, and Meloidogyne incognita-susceptible and -resistant cotton, cowpea, pepper, and tomato for M. floridensis from California.

The host status of carrot, melon, and susceptible and resistant cultivars of tomato, cotton, cowpea, and pepper for a California isolate of the peach root-knot nematode Meloidogyne floridensis was determined in greenhouse pot experiments. It was compared to a race 3 isolate of M. incognita. Melon was an excellent host for both isolates and roots were heavily galled after the 8-week trial. Carrot was a host for M. incognita, but a poor host for M. floridensis, although both isolates caused similar levels of galling. Susceptible cotton was a good host for M. incognita race 3, but a poor host for M. floridensis. Susceptible tomato, cowpea, and pepper were good hosts for both isolates. The M. incognita resistance in tomato and pepper was broken by M. floridensis. Resistant cowpea was a maintenance host as population levels of M. floridensis remained virtually unchanged over the trial period. We conclude that M. floridensis poses a risk to some important vegetable crops in California, as it reproduces on most vegetable crops, including some cultivars that are resistant to M. incognita. On susceptible crops, the reproduction of M. floridensis was always significantly less than that of M. incognita, and we hypothesize that in mixed species field populations, M. incognita will outcompete M. floridensis. This study demonstrates that efforts to limit the spread and prevent further introductions of M. floridensis in California are important to maintain the effectiveness of plant resistance as a nematode management strategy in vegetable crops.

Gene Ontology and pathway enrichment analysis of the upregulated biological Proteins in Single-Line Transgenic Pod Borer Resistant Cowpea

Aim: This research seeks to clarify the proteomic alterations linked to PBR cowpea in comparison to its non-transgenic isoline. Gene Ontology and pathway enrichment analyses were conducted to pinpoint critical biological processes, molecular functions, and cellular components that exhibit upregulation in the transgenic cowpea. Methods: Seeds from both cowpea lines were finely ground, and proteins were extracted utilizing Tris-EDTA and LDS buffers. The proteins were then separated and identified through mass spectrometry (MS), with peptide sequences being matched against protein sequence databases. Results: The enrichment analysis indicated upregulation in pathways associated with pollen tube adhesion, cell-cell adhesion, and biological processes pertinent to both intraspecies and interspecies interactions with no significant difference. Importantly, pathways linked to defense mechanisms against fungi and other organisms were notably enriched, suggesting an enhanced ability to detect and respond to biotic stresses. The results of this study does not underscore any substantial proteomic modifications in the transgenic cowpea. Conclusion: These findings offer valuable targets for genetic engineering and breeding initiatives aimed at creating cowpea varieties with enhanced pest resistance, thus improving crop yield and sustainability. Future investigations should concentrate on validating these proteins and pathways through functional assays and examining their roles in resistance under field conditions.

Identification of resistant cowpea genotypes and aggressiveness of Macrophomina phaseolina isolates by diallel analysis

AbstractCowpea is grown in semiarid regions of Brazil. However, the occurrence of diseases, such as charcoal rot, is one of the main limiting factors to production. Disease is caused by the fungus Macrophomina spp., one of the most important plant pathogens in semiarid conditions. The use of resistant cultivars is the most effective method to control this disease. The objective of this study was to evaluate cowpea lines inoculated with different Macrophomina phaseolina isolates to determine the aggressiveness of the pathogen isolates and the predominant type of resistance in the host. The experiment was carried out in a completely randomized design, using a 5 × 10 factorial scheme with five replications (two plants per pot) in two independent crops. Partial diallel analysis was used to assess the reaction of host genotypes (horizontal and vertical resistance) and the aggressiveness of the isolates. Host reaction and pathogen aggressiveness were analysed by lesion length. Horizontal resistance was observed, corresponding to 56.69% of the variation. The lines L19, L29, L48, and L95 were the most resistant based on estimates of general responsiveness. Among the M. phaseolina isolates evaluated, N105 and ISO16 were the most aggressive based on general aggressiveness ability. By diallel analysis, we identified the most promising genotypes, as well as the most aggressive isolates.

Morphological and biochemical basis of resistance against the pod borers Maruca vitrata F. and Helicoverpa armigera Hübner in cowpea

For determination of morphological and biochemical basis of resistance in cowpea against the pod borers (Maruca vitrata F. and Helicoverpa armigera Hübner), ten cowpea cultivars were evaluated during kharif 2017 and 2018. Results revealed that cultivars having indeterminate growth, yellow flower, light green and short pods as well as long peduncle recorded lower pod borer population. Correlation between different plant morphological characters and the larval population were found non-significant. The cultivars having low protein, high phenol and low total soluble sugars in flowers and immature pods recorded lower the larval population. The correlation between biochemical components of flowers and larval population were found to be non-significant. Biochemical components of immature pods revealed that phenol exhibited significant negative relationship with larval population, whereas, correlation of total soluble sugars of immature pods exhibited significant positive association with larval population. Among the cultivars screened, GC-6 and GC-1605 were found to be consistently resistant based on different morphological and biochemical factors and pod borer infestation. Relatively GC-1609, GC-1611 and GC-2 showed lesser pod borer infestation. GC-1606 was found to be highly susceptible.

Transcriptome analysis of aphid-resistant and susceptible near isogenic lines reveals candidate resistance genes in cowpea (Vigna unguiculata)

BackgroundCowpea (Vigna unguiculata) is a crucial crop for regions of the world that are prone to both heat and drought; however, the phytotoxic cowpea aphid (Aphis craccivora) impairs plant physiology at low population levels. Both antibiotic and antixenotic forms of resistance to the aphid have been mapped to two quantitative trait loci (QTLs) and near isogenic lines (NILs). The molecular mechanism for this resistance response remains unknown.ResultsTo understand the genes underlying susceptibility and resistance, two cowpea lines with shared heritage were infested along a time course and characterized for transcriptome variation. Aphids remodeled cowpea development and signaling relative to host plant resistance and the duration of feeding, with resource acquisition and mobilization determining, in part, susceptibility to aphid attack. Major differences between the susceptible and resistant cowpea were identified including two regions of interest housing the most genetic differences between the lines. Candidate genes enabling aphid resistance include both conventional resistance genes (e.g., leucine rich repeat protein kinases) as well as multiple novel genes with no known orthologues.ConclusionsOur results demonstrate that feeding by the cowpea aphid globally remodels the transcriptome of cowpea, but how this occurs depends on both the duration of feeding and host-plant resistance. Constitutive expression profiles of the resistant genotype link aphid resistance to a finely-tuned resource management strategy that ultimately reduces damage (e.g., chlorosis) and delays cell turnover, while impeding aphid performance. Thus, aphid resistance in cowpea is a complex, multigene response that involves crosstalk between primary and secondary metabolism.

Genotype × Environment Interaction Influence Secondary Metabolite in Cowpea Infested by Flower Bud Thrips

Secondary metabolites are among the major contributors of host-plant resistance. Cowpea produces secondary metabolites that are known to enhance resistance to insect pests including flower bud thrips. However, environmental conditions tend to affect the production of secondary metabolites, thereby affecting the response of the host plants to insect pest. The objective of this study was to determine the effect of the genotype × environment interaction on the production of secondary metabolites and flower bud thrips resistance in cowpea. Six cowpea genotypes were evaluated for flower bud thrips damage and the contents of flavonoids, antioxidants, phenolics, proteins, lignin, tannins and reducing sugars in four environments with varying temperatures and rainfall patterns. The data collected were subjected to the analysis of variance and genotype and genotype × environment (GGE) analysis. Flower thrips damage, and the contents of flavonoids, antioxidants, lignin, tannins and reducing sugars varied significantly (p < 0.001) among genotypes. Genotype Sanzi produced high levels of antioxidants, while TVU-9820 led in phenolic concentrations respectively. Metabolite contents were significantly (p < 0.001) different among environments, with the long rain season of field experiments led to increased production of flavonoids, proteins, lignin and tannins. A resistant genotype, TVU-3804, produced relatively stable contents of flavonoids, antioxidants, phenolics, proteins and reducing sugars across environments. In this study, the environment influenced the concentration of the metabolites, which in turn affected the cowpea’s resistance to flower bud thrips.

Inheritance of Secondary Metabolites Associated With Cowpea Resistance to Flower Bud Thrips

Plant secondary metabolites are part of defense mechanism that form host plant resistance. Understanding the inheritance of secondary metabolites is preliquisite for conducting an effective plant breeding program. The objective of this study was to determine the mode of inheritance of secondary metabolites associated with resistance of cowpea to flower bud thrips. Five cowpea genotypes with varying level of resistance to flower thrips were crossed in full diallel method 1. The F2 were evaluated for secondary metabolites and flower thrips damage in field and screen house. The results confirmed genotype TVU-3804 as resistant, and TVU-9820 and TVU-201 as susceptible to flower bud thrips. Flavonoids, antioxidants, proteins and reducing sugars had significant (p < 0.001) GCA and SCA effects indicating the importance of additive and dominance effect in controlling resistance of flower bud thrips. In addition, significant reciprocal observed for crosses such as Lori Niebe × Sanzi and Sanzi × TVU-3804 for flavonoids and antioxidants is an indication that maternal effect is key in governing resistance of cowpea to thrips. The broad sense heritability was low for secondary metabolites except flavonoid which had moderate value, an indication that delaying selection to a later generation would yield better results while breeding for resistance to flower thrips based on secondary metabolites. The results of this experiment showed that it is possible to use secondary metabolites to breed for improved cowpea resistance to flower bud thrips.

Molecular Characterization of Fusarium and Screening of Cowpea [Vigna unguiculata (L.) Walp.] Germplasms against Fusarium Wilt (Fusarium oxysporum f. sp. Tracheiphilum)

Background: Fusarium wilt caused by fungal pathogen, Fusarium oxysporum is one of the soil-borne diseases that cause 30 to 100% yield reduction with high plant mortality and severe problem in cowpea production. Methods: The Fusarium spp. isolate was obtained from infected cowpea plants and morphological and molecular characterization were done using universal primers. Similarity and phylogenetic evolutionary relationship analysis were performed with database. The fusarium wilt symptoms occurrence in each germplasm were scored using disease rating scale by artificial inoculation of 10% culture. Result: Isolated Fusarium spp. was an anamorphic species with medium growth rate (5 mm/day), characterised by white cottony to pinkish colonies, aseptate microconidia (12.879×3.570 µm) with false head, septate macroconidia (32.409×5.297 µm) along with chlamydospores. While, 90-100% homology was observed between isolate (Accession no: MZ706473) and fusarium reference database. Phylogenetic evolutionary analysis showed that the isolate was closely related to F. oxysporum (OL679453.1) strain supported by 52% bootstrap. Artificial screening of 115 cowpea germplasm under pot culture, identified 18 resistant lines with 0% symptoms. The wilting intensity was maximum during flowering or pod stage than seedling stage in cowpea. The identified resistant cowpea varieties could be used as donor parent in future resistant breeding programmes.

Mapping and Validation of Alectra vogelii Resistance in the Cowpea Landrace B301

Cowpea is the most important food legume in West and Central Africa and a valuable economic commodity in the region. Among the major biotic constraints to cowpea production are root parasitic weeds of which Alectra vogelii (Benth.) is of increasing importance. The cowpea landrace B301 was previously identified as a source of Alectra resistance, but neither the genes nor genomic loci conferring this resistance have been mapped. Therefore, to map and identify genetic markers linked to Alectra resistance for use in the molecular improvement of cowpea, we developed an F2 population from a cross of the susceptible variety 524B with B301. The population was phenotyped for resistance to A. vogelii and genotyped with a cowpea high density single nucleotide polymorphism (SNP) microarray. Putative resistance loci were mapped in F2 populations by categorical trait–multiple interval mapping and validated by selective genotyping. Selective genotyping indicated that the resistance loci on Vu04 (Rav1) and Vu11 (Rav2) were significantly associated with resistance (p ≤ 0.01). Using marker assisted backcrossing, the two resistance loci were introgressed independently into the susceptible 524B genetic background. Phenotyping and genotyping of the segregating backcross families delineated Rav1 to a 10 cM on chromosome 4 and Rav2 to a 6.7 cM interval in chromosome 11. These two loci are desirable for breeding Alectra resistant cowpea varieties due to their simple inheritance and ability to independently confer complete immunity to the parasite.

Identification of Genomic Regions Associated with Fusarium Wilt Resistance in Cowpea

Fusarium wilt (FW), caused by the soil-borne fungal pathogen Fusarium oxysporum f. sp. Tracheiphilum, is a serious threat to cowpea production worldwide. Understanding the genetic architecture of FW resistance is a prerequisite to combatting this disease and developing FW resistance varieties. In the current study, a genetic diversity panel of 99 cowpea accessions was collected, and they were infected by a single strain, FW-HZ. The disease index (DI) based on the two indicators of leaf damage (LFD) and vascular discoloration (VD) varied highly across the population: most accessions were susceptible, and only seven accessions showed resistant phenotypes by both indicators. Through a genome-wide association study (GWAS), 3 and 7 single nucleotide polymorphisms (SNPs) significantly associated with LFD and VD were detected, respectively, which were distributed on chromosomes 3, 4, 5, 6 and 9, accounting for 0.68–13.92% of phenotypic variation. Based on the cowpea reference genome, 30 putative genes were identified and proposed as the likely candidates, including leucine-rich repeat protein kinase family protein, protein kinase superfamily protein and zinc finger family protein. These results provide novel insights into the genetic architecture of FW resistance and a basis for molecular breeding of FW resistant cultivars in cowpea.

Nematode Extract-Induced Resistance in Cowpea against M.Incognita

Every plant in the world has a special defence mechanism to protect themselves from their enemies. In India, total crop losses annually 10-40% by plant-parasitic nematodes. These plant parasitic nematodes are roundworms, which are microscopic in nature. Although there are hundred different kinds of plant parasitic nematodes infect plants, root-knot nematode (Meloidogyne incognita) is one of the serious pest for cowpea plants. They manage to evolve sophisticated defence mechanism for their own protection and also creates interrelationship with the roots of their host plant to form giant cells. They also have the capacity to sense and respond to chemical signals of host plant and by this way they orient themselves within the roots and enhances own survival. Present investigation was carried out to establish the biocontrol potentiality of nematode extract (Meloidogyne sp.) on Vigna unguiculata (cowpea) L.walp variety infected with Meloidogyne incognita (Kofoid& White) Chitwood nematode. The result of in vitro laboratory bioassay showed that application of nematode extract safe for second- stage juveniles (J2) of M. incognita. The result of in vivo test revealed that nematode extract increased growth of inoculated plants in terms of shoot length, shoot weight and root length as compared with inoculated untreated plants. Application of nematode extract showed reduction in root gall number and number of nematode eggs in inoculated roots. In nematode extract treated plants PAL (Phenylalanine ammonia lyase) activity generally increased in the roots which may interfere with infected juveniles at the time of root penetration. Although there are several current management practices have been identified for plant nematode control such as use of botanicles, cultural practices, physical methods, chemical nematicides etc but application of nematode extract is one of new method which ultimately reduces management cost and enhances crop production.

Biology and life table parameters of Callosobruchus maculatus (F.) on Vigna unguiculata (L.) Walp. fertilized with some mineral- and bio-fertilizers

Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae), a major pest of stored cowpea Vigna unguiculata (L.) Walp., causes critical losses by decreasing the grain weight, germination ability and nutritional quality. Improving host plant resistance by the application of appropriate fertilizers would be effective in reducing C. maculatus infestation. The effects of some mineral- (triple superphosphate (TSP) and urea) and bio-fertilizers (Bradyrhizobium japonicum, Pseudomonas putida, mycorrhizal fungi, and a mixture of them) were evaluated on the susceptibility of stored cowpea grains to C. maculatus. Cowpeas fertilized with examined fertilizers were cultivated at farm conditions. Then, the mature, dry grains were harvested and used to investigate the pest's life cycle and life table characteristics under 28 ± 1 °C, 65 ± 5% R.H., and total darkness. Developmental time of C. maculatus on TSP-treated grains was shorter than on control and P. putida treated ones. However, the lowest immature survival and fecundity (number of deposited eggs) was on TSP-fertilized grains. The intrinsic rate of increase (r) and net reproductive rate (R0) were the lowest on the grains treated with TSP. The highest tannins and starch content in the grains fertilized with TSP may be the critical reasons for their resistance to C. maculatus in storage. Application of TSP fertilizer can be recommended to increase cowpea resistance to this pest.

Application of multi‐locus GWAS for the detection of bruchid resistance loci in cowpea (Vigna unguiculata)

AbstractIdentification of genes associated with bruchid resistance variations in cowpea accessions would help breeders to generate new cowpea cultivars with improved resistance and quality. In this work, 107 cowpea collections from various areas in six countries were phenotyped for their responses to Callosobruchus maculatus and genotyped with Single Nucleotide Polymorphism (SNP) markers. Six multi‐locus models Genome Wide Association Study (mrMLM, FASTmrMLM, pKWmEB, pLARmEB, FASTmrEMMA and ISISEM‐BLASSO) were used to associate the genotype data to phenotypic cowpea resistance traits: Percentage of Bruchid Emergence (PBE); Percentage of Weight Loss (PWL); Median Development Period (MDP); Dobie Susceptibility Index (DSI); Number of Egg Laid (NEL) and Mean Number of Hole (MNH). Out of 14 QTNs, three were associated with more than one trait and were associated with 11 candidate genes located within 10–30 kb of the QTNs. These candidate genes exhibit functionalities associated with cowpea resistance mechanisms. All these results could contribute to the gene networks in resistant cowpea varieties. The result of this study could also increase our knowledge of genetic resistance of cowpea to bruchids and could be useful for molecular breeding.

NBS-LRR-WRKY genes and protease inhibitors (PIs) seem essential for cowpea resistance to root-knot nematode

Cowpea (Vigna unguiculata L. Walp) is a legume of great economic importance, however it is highly affected by nematodes. The present work aimed to identify proteins and genes involved in nematode resistance by proteomic and transcriptomic analysis. Plants of a genotype resistant (CE31) to root-knot nematode (Meloidogyne spp.) were collected 12 days after inoculation with Meloidogyne incognita and the total proteins and RNA were extracted from the root samples. Shotgun proteomic analysis was performed using an Orbitrap Elite mass spectrometer and the construction and sequencing of cDNA libraries were carried out in a Hi-Seq 2000 sequencing system. The proteomic and transcriptomic analyses revealed key processes involved in cowpea defense and some interesting candidates were further analyzed by RT-qPCR. Proteins and genes involved in essential biological processes were differentially accumulated such as, regulation of transcription, cell wall stiffening and microtubule-based process. However, the main defense strategies of Vigna unguiculata seem to be focused on the interaction of NBS-LRR and WRKY genes for the activation of R genes, production of protease inhibitors and maintenance of actin cytoskeleton. These are key processes that can culminate in the suppression of giant cell formation and consequently in the development of Meloidogyne incognita. SignificanceIn this study, we identified proteins and transcripts regulated in cowpea resistant to the nematode Meloidogyne spp. upon inoculation. The results revealed key candidate genes involved in the activation of R genes, the production of protease inhibitors and maintenance of the actin cytoskeleton. These processes might be essential for cowpea resistance, as they can impede nematode nutrition, giant cell formation and consequently the development of Meloidogyne incognita.

A Method for Developing RNAi-Derived Resistance in Cowpea Against Geminiviruses.

In plants, RNA interference (RNAi) is triggered by double-stranded RNA (dsRNA). Accordingly, various RNA silencing technologies involving hpRNA, artificial microRNA (miRNA), and virus-induced gene silencing (VIGS) are used for controlling the expression of genes. Such manipulations help understanding gene functions and crop improvement biotechnology. A typical hpRNA construct is comprised of an intron splicable perfect inverted repeat of the target gene sequences under the control of a strong promoter. Geminiviruses, especially Mungbean Yellow Mosaic India Virus (MYMIV) cause devastating diseases in legume plants including cowpea, incurring severe crop loss. RNAi, involving hpRNA construct as transgene, is used to control these diseases at the early stages of geminivirus infection in the host, preventing symptom development and viral DNA accumulation. In this chapter, we describe a detailed protocol for the identification of geminivirus isolates from the filed grown cowpea plants, characterization of virus isolates under the laboratory conditions, design and construct RNAi vectors for effective suppression of viral target genes, and consequent development of transgenic cowpea using Agrobacterium-mediated transformation protocol. These transgenics are subsequently evaluated for resistance to MYMIV.

VBN 3: A new high yielding multiple disease resistant cowpea variety

Cowpea variety VBN 3 (VCP 09-013) is derived from TLS 38 x VCP 16-1. The average yield of VBN 3 is 1013 kg / ha. It is a 17.0 and 17.2 per cent yield increase over VBN 1 (866 kg/ha) and CO (CP) 7 (864 kg/ha), respectively. Duration is 75 – 80 days. It recorded the grain yield of 1148 kg/ha under the irrigated condition which is a 13.8 and 18.0 per cent yield increase over the check varieties VBN 1 (1009 kg/ha) and CO (CP) 7 (973 kg/ ha), respectively. In rainfed conditions, this variety recorded the seed yield of 1013 kg/ha. It is a 17.0 and 17.2 per cent yield increase over the check varieties VBN 1 (866 kg/ha) and CO (CP) 7 (864 kg/ha, respectively. It is having the special features of determinate plant type, synchronized maturity, multiple resistance to bean common mosaic virus, rust and anthracnose diseases. It is resistant to pod borer and pod bug. The cowpea VBN3 is having a protein content of 25.22 per cent. It recorded 100 grain weight of 13.0 g with preferable brown seed colour. It is suitable for cultivation during Rabi season (Purattasi pattam) in Tamil Nadu. Key words: Cowpea, VBN 3, seed yield, rust resistance