Reaction of yellow passion fruit to passion fruit woodiness disease and to bacterial spot / Reação de maracujazeiro azedo à virose do endurecimento dos frutos e à bacteriose

The use of resistant varieties is a promising strategy for passion fruit woodiness disease (PWD) (Cowpea aphid-borne mosaic virus - CABMV) and bacterial spot (Xanthomonas axonopodis pv. passiflorae - Xap) control in yellow passion fruit (Passiflora edulis Sims). This study aimed at evaluating the reaction of nine genotypes of yellow passion fruit to both mechanically inoculated CABMV and Xap, under protected cultivation. The experiment was conducted using a randomized block design with subdivided parcels comprised of nine treatments, four repetitions, six replications per genotype, and five evaluations. Disease incidence (% plants infected) and severity (% of total leaf area with necrotic lesions or leaf symptoms) were calculated at 7-day intervals. All genotypes evaluated were classified as moderately susceptible to PWD. MAR20#10, MAR20#41, and Rosa Intenso were classified as moderately resistant to bacterial spot whereas the remaining genotypes were classified as moderately susceptible. Genotypes Rosa Intenso, MAR20#41, MAR20#15, and MSCA stood out for presenting the lowest PWD mean severity scores as well as the greatest numbers of plants presenting resistance to PWD after five evaluations. MAR20#10, MAR20#41, and Rosa Intenso demonstrated the lowest bacterial spot mean severity scores. Among the genotypes selected, Rosa Intenso and MAR20#41 were the most promising genotypes for presenting the lowest severity scores for both PWD and bacterial spot disease.

O uso de variedades resistentes é uma estratégia promissora para o controle da virose do endurecimento dos frutos (VEF) (Cowpea aphid-borne mosaic virus - CABMV) e da bacteriose (Xanthomonas axonopodis pv. passiflorae - Xap) no maracujazeiro amarelo (Passiflora edulis Sims). Este estudo objetivou avaliar a reação de nove genótipos de maracujazeiro amarelo à CABMV e Xap, ambos inoculados mecanicamente, sob cultivo protegido. O experimento foi conduzido em delineamento de blocos casualizados com parcelas subdivididas, composto por nove tratamentos, quatro repetições, seis plantas por genótipo e cinco avaliações. A incidência (% plantas infectadas) e a severidade (% da área foliar total com lesões necróticas ou sintomas foliares) das doenças foram calculadas em intervalos de sete dias. Todos os genótipos avaliados foram classificados como moderadamente suscetíveis à VEF. MAR20#10, MAR20#41 e Rosa Intenso foram classificados como moderadamente resistente à bacteriose enquanto os demais genótipos foram classificados como moderadamente suscetíveis. Os genótipos Rosa Intenso, MAR20#41, MAR20#15 e MSCA se destacaram por apresentarem menores severidades médias da VEF bem como pelo maior número de plantas apresentando resistência à virose após as cinco avaliações. MAR20#10, MAR20#41 e Rosa Intenso demonstraram as menores severidades médias de bacteriose. Entre os genótipos selecionados, Rosa Intenso e MAR20#41 foram os mais promissores por apresentarem os menores valores de severidade para a VEF e para a bacteriose.

Methodological approaches to assess passion fruit resistance (Passiflora spp. ) to passionfruit woodiness disease / Aspectos metodológicos para avaliação da resistência do maracujazeiro (Passiflora spp. ) à virose do endurecimento dos frutos

The passion fruit woodiness disease, induced by Cowpea aphid borne mosaic virus (CABMV), is considered the most economically important factor limiting passion fruit production in many countries. This study aimed to assess the progression of symptoms caused by CABMV in different Passiflora species. Eighty genotypes belonging 12 species were evaluated in experiments carried out in a completely randomized block design with treatments arranged in a factorial scheme (80 genotypes x 7 evaluation intervals) considering each inoculated plant as a repetition. The disease severity was estimated by the disease index (DI). The evaluations were performed at 20, 27, 34, 41, 48, 55 and 62 days after inoculation (DAI). The average DI values were used to describe the disease progress at each evaluation interval. The shortest time from evaluation to stabilization of CABMV progress was considered to cluster the genotypes by the Scott- Knott test (p0.05) and to classify the genotypes as resistant (R), moderately resistant (MR), moderately susceptible (MS), susceptible (S) or highly susceptible (HS). The mean severity gradually increased in the intervals from 20 to 55 DAI and reached a maximum at 62 DAI. The five classes (R, MR, MS, S and HS) contained about 19, 24, 36, 10 and 11% of the germplasm accessions, respectively. The disease temporal progress was quite variable within and among groups, although no difference in DI was observed in the genotypes after 55 DAI, indicating genotype symptom stabilization at this time, regardless of the genotype resistance level.

O endurecimento dos frutos causada pelo Cowpea aphid borne mosaic virus (CABMV) é considerada a doença mais importante economicamente limitando a produção de maracujazeiro em vários países. O objetivo deste trabalho foi avaliar o progresso dos sintomas causados pelo CABMV em espécies de Passiflora. O estudo foi realizado em delineamento em blocos casualizados, em esquema fatorial (80 genótipos x 7 períodos de avaliação) considerando cada planta como uma repetição, utilizando 80 genótipos pertencente a 12 espécies de maracujazeiro. A severidade foi estimada por meio do índice de doença (ID). As avaliações foram realizadas 20, 27, 34, 41, 48, 55 e 62 dias após a inoculação (DAI). As médias do ID foram utilizadas para verificar a evolução da doença em cada período de avaliação. O período mínimo para estabilização do progresso do CABMV foi utilizado para agrupar os genótipos pelo teste Scott-Knott (p0,05), bem como para classificar os genótipos em resistente (R), moderadamente resistente (MR), moderadamente suscetível (MS), suscetível (S), e altamente suscetível (AS). A severidade média da doença aumentou gradativamente nos intervalos de 20 a 55 DAI e atingiu seu máximo aos 62 DAI. Cerca de 19, 24, 36, 10 e 11% do germoplasma avaliado foi classificado como R, MR, MS, S e AS, respectivamente. O progresso temporal da doença foi bastante variável dentro e entre os grupos, embora não tenha sido observada diferença no ID dos genótipos a partir de 55 DAI, indicando a estabilização dos sintomas a partir deste período, independentemente do nível de resistência do genótipo.

Expression & immunogenicity of malaria merozoite peptides displayed on the small coat protein of chimaeric cowpea mosaic virus.

BACKGROUND & OBJECTIVES: Foreign peptide sequences can be inserted into the betaB-betaC loop of the cowpea mosaic virus (CPMV) small coat protein (SCP) to yield functional chimaeric viruses. Immunisation with chimaeric CPMV elicits immune responses that protect against human immunodeficiency and mink enteritis viruses. The present study was undertaken to investigate the expression of a B cell epitope from the merozoite surface antigen-1 of the malaria parasite Plasmodium falciparum (PfMSP1) in CPMV for an epitope based vaccine. METHODS: DNA encoding a 19 aa sequence (VTHESYQEL VKKLEALEDA, termed P109), the N-terminus of the mature PfMSP1, was cloned into SCP gene yielding a chimaeric virus CPMV-P109. CPMV-P109 was propagated in cowpea plants. The immunogenicity of purified recombinant virus in rabbits was investigated. RESULTS: CPMV-P109 developed a systemically spreading infection in cowpea, with normal viral morphology. The P109 epitope was detected on CPMV-P109 by ELISA with an antiserum produced against homopolymeric P109. Immunisation of rabbits with CPMV-P109 yielded antibodies that, although were predominantly directed against virus-specific epitopes, also recognized the P109 peptide on the recombinant virus and free P109 peptide. These antibodies however, did not react with the native antigen on merozoite by immunofluorescence. INTERPRETATION & CONCLUSION: The results indicate that selecting immunodominant peptide epitopes and presenting them in a near native conformation are important for generating biologically relevant antibodies in the CPMV expression system. Further, the findings draw attention to the importance of measuring immune responses to the viral vector antigens, a preponderance of which can result in undesirable effects such as autoimmunity and hypersensitivity in immunized hosts.

Immune response induced in mice oral immunization with cowpea severe mosaic virus

There is increasing interest in the immune response induced by plant viruses since these could be used as antigen-expressing systems in vaccination procedures. Cowpea severe mosaic virus (CPSMV), as a purified preparation (300 g of leaves, 2 weeks post-inoculation), or crude extract from cowpea (Vigna unguiculata) leaves infected with CPSMV both administered by gavage to Swiss mice induced a humoral immune response. Groups of 10 Swiss mice (2-month-old females) were immunized orally with 10 daily doses of either 50 æg viral capsid protein (boosters of 50 æg at days 21 and 35 after immunization) or 0.6 mg protein of the crude extract (boosters of 0.6 mg at days 21 and 35 after immunization). Anti-CPSMV antibodies were quantified by ELISA in pooled sera diluted at least 1:400 at days 7, 14, 21, 28, 35 and 42 after the 10th dose. IgG and IgA against CPSMV were produced systemically, but IgE was not detected. No synthesis of specific antibodies against the proteins of leaf extracts from V. unguiculata, infected or not with CPSMV, was detected. The use of CPSMV, a plant-infecting virus that apparently does not induce a pathogenic response in animals, induced a humoral and persistent (at least 6 months) immune response through the administration of low antigen doses by gavage. These results raise the possibility of using CPSMV either as a vector for the production of vaccines against animal pathogens or in quick and easy methods to produce specific antisera for viral diagnosis

The 42-kDa coat protein of Andean potato mottle virus acts as a transcriptional activator in yeast

Interactions of viral proteins play an important role in the virus life cycle, especially in capsid assembly. Andean potato mottle comovirus (APMoV) is a plant RNA virus with a virion formed by two coat proteins (CP42 and CP22). Both APMoV coat protein open reading frames were cloned into pGBT9 and pGAD10, two-hybrid system vectors. HF7c yeast cells transformed with the p9CP42 construct grew on yeast dropout selection media lacking tryptophan and histidine. Clones also exhibited ß-galactosidase activity in both qualitative and quantitative assays. These results suggest that CP42 protein contains an amino acid motif able to activate transcription of His3 and lacZ reporter genes in Saccharomyces cerevisiae. Several deletions of the CP42 gene were cloned into the pGBT9 vector to locate the region involved in this activation. CP42 constructions lacking 12 residues from the C-terminal region and another one with 267 residues deleted from the N-terminus are still able to activate transcription of reporter genes. However, transcription activation was not observed with construction p9CP42deltaC57, which does not contain the last 57 amino acid residues. These results demonstrate that a transcription activation domain is present at the C-terminus of CP42 between residues 267 and 374

Inclusion bodies induced by Bean rugose mosaic comovirus seen under light microscopy/

Two types of inclusion bodies were consistently observed under light microscopy in bean (Phaseolus vulgaris) leaf tissue infected with Bean rugose mosaic virus (BRMV), a species of the genus Comovirus, family Comoviridae. One type consisted of vacuolated inclusions found mainly in the cytoplasm of epidermal cells. The other type consisted of abundant crystalloid inclusions of different sizes and shapes found consistently in glandular hairs, guard cells, phloem tissue, xylem elements and occasionally in epidermal and mesophyll tissues. The two types of inclusion bodies stained with Azure A and Luxol Brilliant Green Bl-Calcomine Orange 2RS (O-G), and were similar to those seen to be caused by other species of comoviruses.