Cowpea Aphid-borne Mosaic Potyvirus Research Articles

Viral Diseases of Crops in Nepal

Viral diseases are the important diseases next to the fungal and bacterial in Nepal. The increase in incidence and severity of viral diseases and emergence of new viral diseases causes the significant yield losses of different crops in Nepal. But the research and studies on plant viral diseases are limited. Most of the studies were focused in viral diseases of rice (Rice tungro virus and Rice dwarf virus), tomato (Yellow leaf curl virus) and potato (PVX and PVY). Maize leaf fleck virus and mosaic caused by Maize mosaic virus were recorded as minor disease of maize. Citrus Tristeza Virus is an important virus of citrus fruit in Nepal while Papaya ringspot potyvirus, Ageratum yellow vein virus (AYVV), Tomato leaf curlJava betasatellite and Sida yellow vein Chinaalphasatellite were recorded from the papaya fruit. The Cucumber mosaic virus (CMV) and Zucchini yellow mosaic potyvirus (ZYMV) are the viral diseases of cucurbitaceous crop reported in Nepal. Mungbean yellow mosaic India virus (MYMIV) found to infect the many crops Limabean, Kidney bean, blackgram and Mungbean. Bean common mosaic necrosis virus in sweet bean, Pea leaf distortion virus (PLDV), Cowpea aphid‐borne mosaic potyvirus (CABMV), Peanut bud necrosis virus (PBNV) in groundnut, Cucumber mosaic virus (CMV). Chili veinal mottle potyvirus (CVMV) and Tomatoyellow leaf curl gemini virus (TYLCV) were only reported and no any further works have been carried out. The 3 virus diseases Soyabean mosaic (SMV), Soybean yellow mosaic virus and Bud blight tobacco ring spot virus (TRSV) were found in soybean.Int. J. Appl. Sci. Biotechnol. Vol 6(2): 75-80

Screen-house evaluation of some plant extracts for antiviral properties against cowpea aphid-borne mosaic genus potyvirus in cowpea, Vigna unguiculata l. (walp.)

The purpose of this work is to assess the antiviral properties of ten plant extracts against Cowpea aphid-borne mosaic Potyvirus (CABMV) in Vigna unguiculata var. Crude extracts were obtained from leaves and bulbs of Allium cepa, cloves of A. sativum, leaves of Artemisia annua, leaves and seeds of Azadirachta indica, leaves of Hyptis suaveolens, leaves and seeds of Moringa oleifera and rhizome of Zingiber officinale using water. The virus inoculum was prepared using the extract from the various plant sources and used to mechanically inoculate the test plants of V. unguiculata var. Ife brown in the screenhouse. Infection of test plants by virus was confirmed by the Double Antibody Sandwich Enzyme-Linked Immunosorbent Assay (DAS-ELISA). All the extracts showed varying degrees of inhibition of CABMV on the test plants. However, there was high significant difference between extract from onion leaf and the other treatments. Onion leaf had the lowest virus incidence (19.9%) while others had incidence values ranging from 53 to 77%, with the highest being moringa leaf. Percentage inhibition of onion leaf was 73% compared to other extracts with neem seed having the least inhibition. This study shows that the antiviral properties of onion leaf, Artemisia leaf and onion bulb compare favourably with those of Garlic cloves, Hyptis leaf, Ginger rhizome, Moringa leaf and seeds. The use of onion leaf and bulb in managing CABMV in cowpea plants should be explored.

Transgenic plants expressing the coat protein gene of cowpea aphid-borne mosaic potyvirus predominantly convey the delayed symptom development phenotype.

Cowpea aphid-borne mosaic virus (CABMV) is a potyvirus that infects cowpea causing significant yield reduction. However, there is no durable natural resistance to the virus within the crop and genetic engineering for virus resistance was not possible because of a lack of an efficient, reliable and reproducible cowpea transformation and regeneration protocol. Coat protein-mediated resistance to CABMV was evaluated in Nicotiana benthamiana, a model host for the virus. The CABMV coat protein gene from a Zimbabwean isolate of the virus was optimised for expression in plants under a CaMV 35S promoter and cloned into the Hind III site of the binary vector plasmid pBI121 to result in the plasmid pBI121-CPk. The plasmid pBI121-CPk was used in Agrobacterium-mediated transformation of N. benthamiana leaf sections following the co-cultivation method. Regenerated plants were analysed by PCR and Southern blot hybridisation. R1 seedlings were assayed for kanamycin resistance and for presence of the coat protein and challenged with CAMBV-infected sap. Lines showing delayed symptom development were identified but no line showing immunity was identified. Delayed symptom development is significant resistance since it affords protection to the plants during the crucial early stages of development and exerts little evolutionary pressure on the virus to evolve new strategies.

Screening Cowpea (<I>Vigna unguiculata</I> (l) walp) lines for infection responses to some Cowpea Viruses in Nigeria

Thirty-three cowpea varieties were screened in a screen-house in Ibadan, Nigeria for responses to four cowpea viruses; namely, Bean common mosaic potyvirus - blackeye cowpea strain (BCMV-BlC), Cowpea aphid-borne mosaic potyvirus (CABMV), Cowpea Mottle Carmovirus (CMeV) and Southern bean mosaic sobemovirus (SBMV). 33 x 5 factorial experiment in completely randomised design was used, disease severity was measured at the second and sixth weeks after mechanical inoculation of the viruses and scored from 1 (no infection) to 5 (very severe infection). Symptomless plants were serologically tested with Protein – A sandwich enzyme linked immunosorbent assay (PAS-ELISA) to distinguish lines with latent infection from none infected lines. The yield in 2000 was not significantly (p KEY WORDS: Cowpea viruses, Disease incidence, Cowpea, Vigna, ELISA. Global Jnl Pure and Applied Sciences Vol.10(4) 2004: 473-478

Transgenic plants expressing HC-Pro show enhanced virus sensitivity while silencing of the transgene results in resistance.

Nicotiana benthamiana plants were engineered to express sequences of the helper component-proteinase (HC-Pro) of Cowpea aphid-borne mosaic potyvirus (CABMV). The sensitivity of the transgenic plants to infection with parental and heterologous viruses was studied. The lines expressing HC-Pro showed enhanced symptoms after infection with the parental CABMV isolate and also after infection with a heterologous potyvirus, Potato virus Y (PVY) and a comovirus, Cowpea mosaic virus (CPMV). On the other hand, transgenic lines expressing nontranslatable HC-Pro or translatable HC-Pro with a deletion of the central domain showed wild type symptoms after infection with the parental CABMV isolate and heterologous viruses. These results showed that CABMV HC-Pro is a pathogenicity determinant that conditions enhanced sensitivity to virus infection in plants, and that the central domain of the protein is essential for this. The severe symptoms in CABMV-infected HC-Pro expressing lines were remarkably followed by brief recovery and subsequent re-establishment of infection, possibly indicating counteracting effects of HC-Pro expression and a host defense response. One of the HC-Pro expressing lines (h48) was found to contain low levels of transgenic HC-Pro RNA and to be resistant to CABMV and to recombinant CPMV expressing HC-Pro. This indicated that h48 was (partially) posttranscriptionally silenced for the HC-Pro transgene inspite of the established role of HC-Pro as a suppressor of posttranscriptional gene silencing. Line h48 was not resistant to PVY, but instead showed enhanced symptoms compared to nontransgenic plants. This may be due to relief of silencing of the HC-Pro transgene by HC-Pro expressed by PVY.

Registration of ‘Melakh’ Cowpea

'Melakh' cowpea [Vigna unguiculata (L.) Walp.] (Reg. no. CV- 140, PI 596353) was developed by the Institut Senegalais de Recherches Agricoles (ISRA) as part of a collaborative project with the University of California, Riverside, and was released by the government of Senegal in 1996. Melakh has resistance to cowpea aphid (Aphis craccivora Koch), cowpea aphid-borne mosaic potyvirus (CABMV), and bacterial blight [caused by Xanthomonas campestris pv. vignicola (Burkholder) Dye] and has early maturity

Molecular characterization and interviral homologies of a potyvirus infecting sesame (Sesamum indicum) in Georgia.

Phylogenetic analyses of the 3' terminal region of a potyvirus naturally infecting sesame (Sesamum indicum) in Georgia indicated that the virus belongs to the passionfruit woodiness potyvirus subgroup, and is most closely related to cowpea aphid-borne mosaic potyvirus (CABMV) and South African passiflora potyvirus. Based on the sequence identity, this virus is a strain of CABMV. Use of degenerate primers, reverse transcription-polymerase chain reaction, cloning and sequence analysis allowed us to rapidly determine the taxonomic status of this potyvirus.

First Report of Cowpea Aphid-Borne Mosaic Potyvirus from Cowpeas Grown Commercially in the U.S.

Cowpea aphid-borne mosaic potyvirus (CABMV) is one of several seed-borne viruses known to limit cowpea (Vigna unguiculata (L.) Walp. subsp. unguiculata) production in Africa, Europe, and Asia, but CABMV has not been reported on commercially grown cowpeas in the United States (1). However, a sesame (Sesamum indicum L.)-infecting isolate of CABMV was recently characterized from plants growing near cowpea introduction plots in Georgia (2). In February 1997, we received samples of three seed lots of cowpea cv. Chinese Red that had been harvested in southern Texas during 1996. Approximately 28% of the plants grown from these seed lots expressed strong mosaic symptoms on primary and trifoliate leaves. Viruslike symptoms were reproduced following mechanical transmission to plants of Chinese Red cowpea, Nicotiana benthamiana, and soybean (Glycine max L.) cv. Lee. When Coronet and Pinkeye Purple Hull-BVR cowpeas were inoculated with sap extracts from symptomatic Chinese Red plants, chlorotic lesions developed on inoculated leaves, but only Coronet plants supported symptomless systemic infections. Similarly inoculated plants of Chenopodium quinoa (L.) and common bean (Phaseolus vulgaris L.) cvs. Pinto and Black Valentine developed localized chlorotic lesions. In Ouchterlony gel diffusion assays, extracts from symptomatic cowpea plants did not react with antisera to blackeye cowpea mosaic potyvirus (BlCMV), cucumber mosaic cucu-movirus (CMV), southern bean mosaic sobemovirus, cowpea mosaic comovirus, cowpea severe mosaic comovirus, or cowpea chlorotic mottle bromovirus. In the indirect enzyme-linked immunosorbent assay, sap extracts from symptomatic plants reacted with antiserum to CABMV, giving OD values at A405 of 0.10 to 0.25, and reacted weakly with antiserum to BlCMV, with OD values at A405 less than 0.035. Extracts from healthy control plants gave OD values at A405 less than 0.010. No positive reactions were obtained with antisera to bean yellow mosaic potyvirus, peanut mottle potyvirus, soybean mosaic potyvirus, or CMV. To our knowledge, this is the first report of CABMV in commercially grown cowpea from the U.S.

Survey on cowpea virus incidence and distribution in Nigeria

Enzyme-linked immunosorbent assay (ELISA) was used to detectviruses in649 cowpea leafsamples collectedfrom115 fields during a 3-year survey carried out from 1991 to 1993 throughout all agroecological zones in Nigeria. Six viruses, cowpea aphid-borne mosaic potyvirus (CAMV), blackeye cowpea mosaic potyvirus (BICMV), southern bean mosaic sobemovirus (SBMV), cowpea mottle carmovirus (CMoV), cowpea (yellow) mosaic comovirus (CpMV) and the cowpea strain of cucumbermosaic cucumovirus (CMV-CS)were detectedin 390 outofthe 649 samples assayed. There was considerable variation in both disease incidence and virus distribution in the different crop habitats within and between seasons. Thus, while SBMV had the highest incidence (27.4%) and was the most prevalent (66.7% in 1991, CAMV had the highest incidences (11.3% and 28.8%, respectively) and was the most prevalent 33% and 68%, respectively) in 1992 and 1993. CpMV and CMoV remained consistently moderate both in incidence and prevalence throughout the duration of the survey. The detection of the three beetletransmitted sphericalviruses (SBMV, CpMV and CMoV)in the Sudanand Sahel Savanna indicates that there is no ecological restriction to the distributionofanyoftheviruses.Incidence ofmultipleinfectionofuptofour and five viruses in individual samples was observed, but mixed infection with two viruses was more prevalent (13%). The potential for horizontal resistance breeding based on common vector transmission is discussed.

Identification and characterization of viruses infecting bambara groundnut (Vigna subterranea) in Nigeria

Eight viruses were identified infecting bambara goundnut in farmer's fields in Nigeria: cowpea aphid-borne mosaic potyvirus, blackeye cowpea mosaic potyvirus, peanut mottle potyvirus, cowpea mottle carmovirus, cowpea mosaic comovirus (cowpea yellow mosaic virus), cowpea mild mottle carlavirus, cucumber mosaic cucumovirus and southern bean mosaic sobemovirus. The importance of these viruses to the crop is discussed and details on their ecology and geographical distribution are given.

Sources of genetic resistance in cowpea (Vigna unguiculata (L.) Walp.) to cowpea aphid-borne mosaic potyvirus

Fifty-one cowpea (Vigna unguiculata (L.) Walp.) genotypes were tested by mechanical inoculation with seven geographically diverse isolates of cowpea aphid-borne mosaic potyvirus to identify resistant sources. Of 51 genotypes three, TVu-401, TVu-1582 and TVu-1593 were found immune to all the seven isolates. Forty-five genotypes gave different reactions to individual isolates. Several immune, resistant and tolerant genotypes against each isolate were identified. A considerable evidence of pathogenic variability among the virus isolates was also observed.

Sequence of the 3'-terminal region of a Zimbabwe isolate of cowpea aphid-borne mosaic virus (CABMV).

The 3'-terminal 1221 nucleotides of a Zimbabwe isolate of cowpea aphid-borne mosaic potyvirus (CABMV) genome have been sequenced. The sequence comprises an open reading frame (ORF) of 990 nucleotides and a 3' non-coding-region of 231 nucleotides followed by a poly-A. The ORF has high similarity to NIb and coat proteins (CP) of potyviruses. A potential CP Q/S cleavage site was identified, yielding a CP of 30.5 kDa containing 275 amino acids. The CABMV sequence is closely related to that of South African passiflora virus (SAPV) which should therefore be regarded as a strain of CABMV.

Some studies on cowpea aphid‐borne mosaic and pea seed‐borne mosaic potyviruses in Nepal

Abstract Various virus‐like symptoms were recorded on field‐grown cowpea (Vigna unguiculata L. Walp) and pea (Pisum sativum L.) during 1989–1990 at the experimental farm of the Institute of Agriculture and Animal Sciences (IAAS), Rampur, Chitwan valley, in the central terai plains of Nepal. The causal agent(s) causing narrow and/or curled leaves, and stunting of pea, and prominent mosaic and vein banding of cowpea were transmitted by both aphids and sap inoculations. Electron microscopic examination of leaf extracts from affected cowpea and pea plants revealed the presence of flexuous filamentous virus particles c. 700 nm long, similar to those of potyviruses. The virions in the leaf extracts from cowpea samples reacted strongly to antibodies against cowpea aphid‐borne mosaic potyvirus (CABMV) in immunosorbent electron microscopy, while the extract from the pea samples reacted strongly to antibodies against pea seed‐borne mosaic potyvirus (PSbMV) in enzyme‐linked immunosorbent assay (ELISA). Time of plant...

Seedborne Viruses in Preintroduction Cowpea Seed Lots and Establishment of Virus-Free Accessions

Seeds from 60 cowpea preintroductions from Botswana, India, and Kenya were increased at the University of California Riverside. Second generation seed were planted in insect-free greenhouses at two locations and resulting seedlings were assayed by direct antigen coated enzyme-linked immunosorbent assay (DAC-ELISA) for the presence of eight seedborne viruses. By visual selection and DAC-ELISA, 10 virus-free mother plants for each of the 60 accessions were established. The seedlots from these mother plants were subsquently planted in isolation plots at St. Croix, Virgin Islands. Seedlings from the St. Croix seed increase were observed and tested by DAC-ELISA and were found to have remained free from viruses during this field exposure. One or more of the following viruses were detected in 40 of the 60 preintroductions: 32 containing cowpea aphid-borne mosaic potyvirus (possibly blackeye cowpea mosaic potyvirus in some cases); 23 with cowpea severe mosaic comovirus; 22 with southern bean mosaic sobemovirus; seven with cucumber mosaic cucumovirus; and seven with cowpea mottle carmovirus. None were found to contain ELISA-detectable cowpea mosaic comovirus or cowpea mild mottle carlavirus. Twenty preintroductions were free of ELISA-detectable seedborne viruses. Virusfree experimental seed lots were produced for limited use by interested cowpea breeders

Inheritance of resistance to potyviruses in Phaseolus vulgaris L. III. Cosegregation of phenotypically similar dominant responses to nine potyviruses

We have identified monogenic dominant resistance to azuki bean mosaic poty virus (AzMV), passionfruit woodiness potyvirus-K (PWV-K), zucchini yellow mosaic potyvirus (ZYMV), and a dominant factor that conditioned lethal necrosis to Thailand Passiflora potyvirus (ThPV), in Phaseolus vulgaris 'Black Turtle Soup 1'. Resistance to AzMV, PWV-K, ZYMV, watermelon mosaic potyvirus, cowpea aphid-borne mosaic potyvirus, blackeye cowpea mosaic potyvirus, and lethal necrosis to soybean mosaic potyvirus and ThPV cosegregated as a unit with the I gene for resistance to bean common mosaic potyvirus.

Cowpea Viruses in Senegal, West Africa: Identification, Distribution, Seed Transmission, and Sources of Genetic Resistance

Viral diseases of cowpea (Vigna unguiculata subsp. unguiculata) in Senegal were surveyed during the rauny seasons of 1990 and 1991. Sixty-six symptomatic plant samples from five production areas were assayed for seven viruses by enzyme-linked immunosorbent assay (ELISA). Four recognized viruses, cowpea aphid-borne mosaic potyvirus (CABMV), cowpea mottle carmovirus (CPMoV), cowpea severe mosaic comovirus (CSMV), and southern bean mosaic sobemovirus (SBMV), were detected in 34, 2, 1, and 1 samples, respectively. All are seed-transmissible in cowpea. Variants of an unknown potyvirus were also detected in 21 samples. These variants occurred principally in new, improved CABMV-resistant cowpea genotypes, and their combined incidence in plant samples was exceeded only by CABMV