Genira Pereira de Andrade

Cowpea aphid-borne mosaic virus (CABMV) is widespread in passionfruit in Brazil and causes passionfruit woodiness disease

Summary.Leaf samples of yellow passionfruit (Passiflora edulis f. flavicarpa) displaying fruit woodiness symptoms were collected in seven Brazilian states and the Federal District. Viral infection was confirmed by host range and ELISA, and fourteen viral isolates were obtained. All isolates were capable of infecting several leguminous host species, although differences in symptom severity were noticeable. Woodiness symptoms were reproduced in yellow passionfruit, and mosaic symptoms were induced in common bean. All isolates infected cowpea, reported as a non-host of passion fruit woodiness virus (PWV). Indirect ELISA demonstrated that all isolates were serologically related to each other and also to cowpea aphid-borne mosaic virus (CABMV). The complete sequence of the capsid protein was determined for all isolates. Comparison of these sequences with those of other potyviruses indicated the highest identity with CABMV isolates (85 to 94%). Identity with PWV isolates ranged from 54 to 70%. Phylogenetic analysis grouped all of the Brazilian isolates in a monophyletic cluster with the CABMV isolates, clearly distinct from the PWV isolates. Furthermore, this analysis demonstrated that a group of previously characterized isolates from Brazil that had been designated as PWV should be reclassified as CABMV. Together, these results provide unequivocal evidence that, in Brazil, passionfruit woodiness disease is primarily caused by CABMV. The presence of PWV in Brazil has yet to be confirmed.

Stock indexing and Potato virus Y elimination from potato plants cultivated in vitro

Potato cultivars (Solanum tuberosum L.) have shown degeneration or run out caused by viruses after several cycles of propagation using seed tubers from commercial fields. This work reports the occurrence of single and mixed infections of four potato viruses in Paraiba-Brazil and presents a method for Potato virus Y (PVY) elimination, by using thermo-and chemotherapies. Plants of potato cv. Baraka were tested by direct antigen coating ELISA. Antisera against PVY, Potato virus X (PVX), Potato virus S (PVS), and Potato leafroll virus (PLRV) were used. Materials with positive reaction to PVY were treated for virus elimination. Single node cuttings (1.0 cm length) were excised and inoculated in Murashige & Skoog (MS) medium, supplemented with 1.0 mg L-1 of kinetin, 0.001 mg L-1 of naphthalene acetic acid (NAA) and 0.1 mg L-1 of gibberellic acid (GA3). The thermotherapy at approximately 37oC, during 30 and 40 days, resulted in 20.0 and 37.5% PVY elimination, respectively. Chemotherapy was undertaken with Ribavirin (RBV), 5-Azacytidine (AZA), and 3-Deazauridine (DZD). The RBV showed the highest rate of virus eradication, with 55.5% virus-free plants. Simultaneous thermo and chemotherapy had higher efficiency for the elimination of PVY, reaching rates of healthy plants of 83.3% with RBV, 70.0% with AZA, and 50.0% with DZD.

Análise Filogenética de Potyvírus Causando Endurecimento dos Frutos do Maracujazeiro no Nordeste do Brasil

Leaf samples of yellow passionfruit plants (Passiflora edulis f. flavicarpa) showing woodiness symptoms in the fruit were collected in fields located in the states of Pernambuco, Paraiba and Sergipe. Virus infection was confirmed by serology and inoculation of indicator plants. The six viral isolates obtained from passionfruit were capable of infecting several plant species, although a difference in the intensity of symptoms induced by each isolate was observed in some hosts. Indirect ELISA showed that the passionfruit isolates were serologically related to each other, and also to the potyvirus Cowpea aphid-borne mosaic virus (CABMV). The amino acid sequence of the capsid protein was determined for the six isolates. Sequence comparisons with other potyviruses indicated a maximum degree of identity with CABMV (86 to 94%). Sequence identity with isolates of Passionfruit woodiness virus (PWV) ranged from 68 to 76%. Phylogenetic analysis based on the amino acid sequences confirmed that the Brazilian passionfruit isolates are closely related to CABMV, and only distantly related to PWV. Together, these results indicate that the potyvirus isolates obtained from passionfruit comprise a strain of CABMV.

ARRANJO ESPACIAL DO VIRA-CABEÇA DO FUMO EM ARAPIRACA, ESTADO DE ALAGOAS*

The spotted wilt of tobacco (Nicotiana tabacum), caused by Groundnut ringspot virus (GRSV), genus Tospovirus, has been observed with high severity in certain areas of the tobacco producing region of Alagoas. The spatial pattern of the disease was analysed in two areas (A and B), formed by four parcels each, located in the county of Arapiraca. The parcels were evaluated weekly by spatial mapping of healthy and spotted wilt tobacco plants, as well as by the disease incidence, represented by the number of plants with symptoms in relation to the total evaluated plants. Through the analyses of ordinary runs and spatial autocorrelation, a random pattern diseased plants was predominantly observed, although aggregation was also detected in a few cases. Although the possible effect of infected seedlings in the spatial pattern was not discarded, the most probable hypothesis is that the infections mainly occurred due to the primary inoculum transmitted by viruliferous thrips entering the parcels from external reservoirs.

Complete genome sequence of melon yellowing-associated virus from melon plants with the severe yellowing disease in Brazil

Here, we describe the complete genome sequence of melon yellowing-associated virus (MYaV), found in melon plants with severe yellowing disease, determined by high-throughput and Sanger sequencing. MYaV has an RNA genome of 9073 nucleotides plus a poly(A) tail. At least six open reading frames were predicted, with a typical carlavirus genomic organisation. Phylogenetic analysis of the complete genome sequence and the amino acid sequences of the RNA-dependent RNA polymerase confirmed that MYaV belongs to the genus Carlavirus, with the highest genome-wide nucleotide sequence identity of 59.8% to sweet potato yellow mottle virus.