Ricardo Gioria

Comparative Cytopathology and Immunocytochemistry of Japanese, Australian and Brazilian Isolates of Orchid fleck virus

Cytopathic effects in orchid leaf tissues infected with Australian, Japanese and Brazilian isolates of Orchid fleck virus (OFV) were indistinguishable and like those previously described in the literature. Cells had an electron-lucent viroplasm with unenveloped rod-shaped virions in the nucleus and cytoplasm, often associated with the inner membrane of the nuclear envelope and the endoplasmic reticulum. Antiserum raised against a Japanese isolate of OFV reacted with Brazilian and Australian isolates in ELISA, and when used for immuno-gold labelling, also reacted in situ with the rod-shaped virions and the intranuclear viroplasm of all three isolates. These results suggest that the viroplasm is where structural proteins accumulate and virions are formed.

Occurrence of Tomato chlorosis virus in tomato crops in five Brazilian states

Tomato chlorosis virus (ToCV) is a species in the genus Crinivirus, transmitted by Bemisia tabaci biotype B, first detected in Brazil in 2006 in the county of Sumare, State of Sao Paulo. During the period from 2007 to 2010, RT-PCR analyses followed by nested-PCR with specific primers for ToCV detection, and sequencing of the amplicons, confirmed the presence of this virus in samples of symptomatic tomato plants (Solanum lycopersicum) from crops in counties in the states of Bahia (BA), Espirito Santo (ES), Goias (GO), Minas Gerais (MG), and Rio de Janeiro (RJ). This is the first ToCV report for the states of BA, ES, GO, MG, and RJ, suggesting that this virus is widely disseminated in Brazil.

A classification of Pepper yellow mosaic virus isolates into pathotypes

Pepper yellow mosaic virus (PepYMV) is the most important potyvirus infecting sweet pepper in Brazil. In this study, twenty isolates of PepYMV were obtained from commercial sweet pepper crops. To confirm virus identity, the coat protein gene was completely sequenced for eleven of these isolates, and partially sequenced for the other nine isolates. The amino acid identities obtained were above 93% when compared with the sequence of a characterized PepYMV isolate (AF348610). Extracts of Nicotiana tabacum cv. TNN plants infected with the different isolates were used to inoculate the differential series of Capsicum spp cultivars containing the genes pvr21, pvr22, pvr23, pvr24, and Pvr4. Using the same criteria established for Potato virus Y (PVY), fourteen isolates of PepYMV could be classified as known pathotypes described for PVY, that is: 1.2 (2 isolates), 1.3 (6) and 1.2.3 (6). The remaining six isolates, 1.3 (2) and 1.2.3 (4) could not be classified into the typical pathotypes of PVY because they were also virulent on Serrano Criollo de Morellos—334 (C.M 334) which carries the pvr23 and Pvr4 genes. To classify the PepYMV into pathotypes and counter the biological diversity found in this species we propose the utilization of 2x for the ability to overcome the correspondent allele of the pvr2 locus and 4 for the capacity to break down the Pvr4 gene. Using this criterion we could classify the PepYMV into five pathotypes: 21.22; 21.23; 21.22.23; 21.23. 4 and 21.22.23. 4.

Avaliação de danos causados pelo Tomato severe rugose virus (ToSRV) em cultivares de pimentão

Tomato severe rugose virus (ToSRV) is the predominant species of begomovirus affecting pepper crops in Sao Paulo State, Brazil. Its occurrence is relatively recent for the culture thus, there is no information on yield losses caused by this virus on sweet pepper. The aims of this study were to evaluate yield and fruit fquality of three pepper cultivars (Magda, Amanda and Rubia R) infected with ToSRV. There was marked reduction in the number of fruits and in the growth of plants; however, ToSRV did not significantly influence the average weight, diameter and the length of fruits. The results obtained so far lead to the conclusion that ToSRV causes damage in peppers and it is necessary the development of resistant cultivars to ToSRV.

Yield of varieties of Cucurbita pepo preimmunized with mild strains of Papaya ringspot virus - type W and Zucchini yellow mosaic virus

Papaya ringspot virus - type W (PRSV-W) and Zucchini yellow mosaic virus (ZYMV) are the most prevalent viruses in cucurbit crops in Brazil and responsible for frequent yield losses. Diseases caused by these viruses are difficult to control. The objective of this work was to evaluate the effects of mild strains PRSV-W-1 and ZYMV-M on the yield of Cucurbita pepo L. cvs. Samira, Novita Plus, AF 2847, and Yasmin, under plastic greenhouse and field conditions. Plants infected with ZYMV-M and grown in a plastic greenhouse did not exhibit typical leaf symptoms or significant alterations in quantitative and qualitative fruit yield. However, when infected with PRSV-W-1, or PRSV-W-1 + ZYMV-M, the plants exhibited severe leaf mosaic symptoms and reduced fruit quality, although there were no changes in the number and mean fruit weight harvested from these plants. When these plants were infected with PRSV-W-1 and studied simultaneously in the field and plastic greenhouse, intensification of symptoms in the fruits and leaves was more pronounced under the greenhouse conditions. Quantitative yield did not change. Environmental factors seem to influence symptoms induced by PRSV-W-1.

Resistance of Xanthomonas euvesicatoria strains from Brazilian pepper to copper and zinc sulfates

Bacterial spot, caused by Xanthomonas spp., is one of the major bacterial diseases in pepper (Capsicum annuum L.). The infection results in reduced crop yield, particularly during periods of high rainfall and temperature, due to the low efficiency of chemical control with copper bactericides. This study evaluated the copper and zinc sulfate sensitivity of 59 pathogenic strains of Xanthomonas euvesicatoria isolated from pepper plants produced in various regions throughout Brazil. Both the respective sulfates and a mixture thereof was evaluated at 50, 100, 200 and 400 μg.mL-1. All the evaluated strains were found to be resistant to zinc sulfate (100 μg.mL-1) and 86.4% were resistant to copper sulfate (200 μg.mL-1). The mixture of copper (200 μg.mL-1) and zinc (200 μg.mL-1) sulfates inhibited the growth of all strains of X. euvesicatoria. To our knowledge this is the first study to report the resistance of X. euvesicatoria strains from pepper plants to copper and zinc sulfates in Brazil.

Evaluation of resistance to Tomato severe rugose virus (ToSRV) in Capsicum spp. genotypes

Tomato severe rugose virus (ToSRV) is the predominant species of begomovirus in Sao Paulo State, Brazil, and infects primarily tomato and pepper plants. There is no information about genetic resistance of pepper to this virus, so in this work the reaction of 29 genotypes of Capsicum spp. was evaluated by inoculation of two ToSRV isolates: ToSRV-Sk (isolated from a tomato plant) and ToSRV-PJU (isolated from a pepper plant). For both isolates, two C. annuun genotypes (Catarino Cascabel - Mexico and Silver) showed no symptoms 30 days after inoculation (d.a.i). In a second experiment, these two genotypes were evaluated for 150 d.a.i and, again, no symptoms could be observed. However, the virus was detected by RCA-PCR, indicating that both genotypes are susceptible, but less affected by ToSRV infection. Catarino Cascabel - Mexico and Silver can be indicated for use in breeding programs for resistance of pepper to ToSRV.

First report of Tomato spotted wilt virus (TSWV) infecting Campanula medium in Brazil.

Plantas de campânula (Campanula medium) exibindo mosaico e necrose foliar e aneis em flores foram coletadas em uma estufa comercial de flores na regiao de Atibaia, SP. Suspeitando de possivel etiologia viral, amostras de tecido lesionado foram analisadas por ensaios de transmissao mecânica, microscopia eletronica e sorologia. Todos os resultados apontaram para a presenca do Tomato spotted wilt virus (TSWV) como o responsavel pelos sintomas. Esse e o primeiro relato deste patogeno em campânula no Brasil.

Identification of Capsicum accessions tolerant to Tomato severe rugose virus and resistant to Bemisia tabaci Middle East-Asia Minor 1 (MEAM1)

The whitefly Bemisia tabaci is one of the most important pests of solanaceous crops worldwide, mainly due to its ability to transmit different viruses, including begomoviruses. Tomato severe rugose virus (ToSRV) is the prevalent begomovirus in southeastern and central Brazil, and affects economically important vegetable crops such as tomato and pepper. Here we evaluated 36 pepper accessions comprising four species (Capsicum annuum, C. frutescens, C. chinense and C. baccatum) for ToSRV and B. tabaci resistance, through free-choice and non-choice tests. The accessions IAC-1544 (C. frutescens), IAC-1545 and 1549 (C. chinense), IAC-1551, 1566 and 1579 (C. annuum) were infected by ToSRV but did not show any symptoms. Among them, IAC-1544, IAC-1545, IAC-1551 and IAC-1579 displayed significant differences in whitefly egg-laying preference in the free-choice test. In the non-choice test, IAC-1544, IAC-1545 and IAC-1579 displayed similar reaction, being unattractive to the insects and exhibiting reduced oviposition rates. Low survival of nymphs and high mortality were observed in accessions IAC-1544, IAC-1545, IAC-1549, IAC-1551, IAC-1566 and IAC-1579, suggesting the involvement of antibiosis mechanisms. The accessions IAC-1544, IAC-1545 and IAC-1579 could be classified as good sources of resistance to both ToSRV and B. tabaci.

Estimativas de capacidades de combinação em cebola para resistência a raíz rosada e caracteres agronômicos

Aimed at estimating the combining abilities for pink root resistance and agronomic traits in onion (Allium cepa L.), the present study was carried out by using partial diallel scheme. Two partially endogamic inbred line groups were used as parents. Group I consisted of five male-sterile female inbred lines, originated from a Brazilian Tropical Onion Population, selected for sowing during the summer. Group II consisted of ten male inbred lines, most of which originated from Crioula onion populations, obtained by successive self-pollination and kept by mass selection within lines. The following traits were evaluated: pink root resistance using a score scale from 1 to 5, leaf vigor, leaf architecture, number of leaves, plant height (cm), total number of bulbs and total weight of bulbs (kg). Experimental design was in randomized blocks with three replicates. There were additive effects on pink root resistance and considerable non-additive effects for some combinations; the same genetic behavior was found for the other agronomic traits of interest. Thus, intrapopulation selection can be done with the inbred lines used in the current study and hybrids of high level of pink root resistance, as well as good agronomic traits, can be obtained.