José Albérsio de Araújo Lima

Serological survey of virus in cucurbit species in the Lower Middle São Francisco River Basin, Brazil

Aiming to get information about the virus that most frequently infects cucurbit plants of the species Benincasa hispida,Citrullus spp., Cucurbita spp., Cucumis melo, Lagenaria sp., Momordica charantia and also some F1 hybrids of C. lanatus with C. lanatus var. citroides in irrigated areas of Petrolina-PE and Juazeiro-BA, experimental and farming areas were surveyed in the first and second half of each year (2005 to 2007). The samples were tested by indirect enzyme-linked immunosorbent assay (ELISA) against antisera specific for Papaya ringspot virus, type watermelon(PRSV), Watermelon mosaic virus (WMV), Zucchini yellow mosaic virus (ZYMV) and Cucumber mosaic virus (CMV), and by Agar Double Diffusion against antiserum specific for Squash mosaic virus (SqMV) at the Plant Virus Laboratory of the Federal University of Ceara. Leaf samples from 967 plants were analyzed and 608 of them were infected. Among 125 samples from symptomless plants, 42 allow replication. PRSV-W was predominant, followed by WMV and ZYMV, and mixed infections occurred in all infected species. CMV was detected only in one sample and SqMV was not found. This is an indication that a breeding program for virus resistance in cucurbit species in the region must consider the three potyviruses.

Resistência simples e múltipla a vírus em genótipos de caupi

The objective of this work was to identify new sources of simple and multiple resistances to Cowpea severe mosaic virus (CPSMV), Cowpea aphid-borne mosaic virus (CABMV) and Cucumber mosaic virus (CMV) isolates in cowpea (Vigna unguiculata). Thirty-three genotypes from the germplasm bank of Universidade Federal do Ceara were tested as to their resistance to four CPSMV isolates, two CABMV isolates and one CMV isolate. Twenty-five days after the first virus inoculations, all inoculated plants, including the asymptomatic ones, were tested by serology. Genotypes were classified as: immune, plants without symptoms and negative serology; resistant, plants with mild mosaic and positive serology; susceptible, plants with mosaic and positive serology; and highly susceptible, plants with severe mosaic, other systemic symptoms, including systemic necrosis, and positive serology. Simple and multiple resistances to viruses were identified among the evaluated genotypes, but none of them showed multiple immunities to all isolates. Four genotypes showed immunity to all CPSMV isolates, two were immune to CABMV and two showed immunity to CMV. Eleven genotypes showed multiple resistances to two viruses, allowing for the development of new cultivars with more stable and broader resistance. Genotypes Purple Knuckle Hull-55, MNC-03-731C-21 and CNCx284-66E show resistance to CABMV, even when inoculated with CMV.

Molecular flexibility and structural instabilities in crystalline l-methionine.

We have investigated the dynamics in polycrystalline samples of l-methionine related to the structural transition at about 307K by incoherent inelastic and quasielastic neutron scattering, X-ray powder diffraction as well as ab-initio calculations. l-Methionine is a sulfur amino acid which can be considered a derivative of alanine with the alanine R-group CH3 exchanged by CH3S(CH2)2. Using X-ray powder diffraction we have observed at ~190K an anomalous drop of the c-lattice parameter and an abrupt change of the β-monoclinic angle that could be correlated to the anomalies observed in previous specific heat measurements. Distinct changes in the quasielastic region of the neutron spectra are interpreted as being due to the onset and slowing-down of reorientational motions of the CH3-S group, are clearly distinguished above 130K in crystalline l-methionine. Large-amplitude motions observed at low frequencies are also activated above 275K, while other well-defined vibrations are damped. The ensemble of our results suggests that the crystalline structure of l-methionine is dynamically highly disordered above 275K, and such disorder can be linked to the flexibility of the molecular thiol-ether group.

Biological, serological and molecular comparison between isolates of Cowpea severe mosaic virus.

ABSTRACT Cowpea, Vigna unguiculata, can be affected by several diseases, and those caused by viruses are considered of great importance. Cowpea severe mosaic virus (CPSMV), which belongs to the family Comoviridae, genus Comovirus, stands out for its severity and degree of incidence. Its genetic variability can give rise to different strains around the world, including in Brazil. The objective of the present research was to establish a biological, serological and molecular comparison between five CPSMV isolates obtained from naturally infected plants in different States of the Northeast of Brazil. Isolates were obtained from cowpea: CPSMV-AL (State of Alagoas), CPSMV- CE (Ceara); CPSMV-MC (Piaui), CPSMV-PE (Pernambuco) and an isolate obtained from Crotalaria paulinea, in the State of Maranhao - CPSMV-CROT. A host range study evidenced biological differences among the virus isolates, especially in cowpea genotypes. The isolates were showed to be serologically and molecularly related by polymerase chain reaction �� PCR, using degenerated primers which amplified two conserved regions in the coat protein and in the replicase genes. Cloning and sequence of CPSMV-PE made possible its comparison with other CPSMV isolates and other virus species from the genus Comovirus.

Sequence variability in the coat protein gene of Cowpea severe mosaic virus isolates from northeastern Brazil

The comovirus Cowpea severe mosaic virus (CPSMV) causes a disease in cowpea (Vigna unguiculata) but, despite its importance, there are no studies on the genetic diversity of viral populations. We have determined the nucleotide sequences of part of the coat protein (CP) gene of six Brazilian isolates of CPSMV. Genomic fragments (521 nucleotides) were RT-PCR amplified, cloned, and their sequences were compared with each other and with other comoviruses. Sequence comparisons indicated a high degree of conservation for the CP gene, with 92-100% nucleotide and 97-100% amino acid sequence identity among the isolates. There was no correlation between geographical origin and sequence identity or phylogeny among the isolates.

Melão tupã: produtividade, qualidade do fruto e resistência a viroses

Progenies of melon (Cucumis melo L.) cv. Tupa, that associate the favorable fruit characteristics of yellow casaba cantaloupe types, were submitted to artificial inoculation with five virus: Watermerlon mosaic virus (WMV-2), Papaya ringspot virus (PRSV-W), Zucchini yellow mosaic virus (ZYMV), Squash mosaic virus (SqMV) and Cucumber mosaic virus (CMV), in greenhouse. Yield and the fruit quality were evaluated in the field. Progenies of three families showed marked resistance to PRSV-W and to ZYMV, also some manifested resistance to WMV-2. More than 50% showed isolated resistance to PRSV-W (63,15%) and to ZYMV (52,63%). The resistance to both PRSV-W and ZYMV occurred in 42,10% of the progenies and the triple resistance to PRSV-W, ZYMV and to WMV-2 was detected in 36,84%. One progeny was resistant to four viruses (PRSV-W, ZYMV, WMV-2 and CMV). The progenies were very variable on harvesting date, some being very dispersed for harvest, others with no fruits harvested before 80 days, and others presenting a highly concentrated harvest period. In comparison to the yellow casaba melon, the progenies were very late in fruit maturation, but similar for fruit weight, fruit shape, flesh thickness and internal diameter cavity. Flesh firmness varied from 7,78 N to 35,6 N, and 20% of these progenies presented the firmness superior to 20 N, very similar to cantaloupe melon type.

The presence of Papaya ringspot virus and Papaya lethal yellowing virus in commercialized papaya fruits

Considering the high incidence of virus in papaya (Carica papaya) orchards and their typical symptoms in the fruits, a survey was carried out in the Central Market in the State of Ceara (CEASA) for the presence of papaya fruits infected with Papaya ringspot virus (PRSV) and Papaya lethal yellowing virus (PLYV). CEASAs are the most important fruit commercial centers, and a great number of plant products sold in supermarkets are obtained in CEASA. Fruits were randomly collected from CEASA stalls and brought to the Plant Virus Laboratory at the Federal University of Ceara (UFC) to be analyzed for typical virus symptoms and tested by indirect enzyme linked immunosorbent assay (ELISA) against antisera specific to PRSV and PLYV. According to the results obtained by symptom analysis, which were confirmed by serology, among the 8,400 fruits analyzed 5.5% were infected with PRSV and 1.2% with PLYV, showing the need to implement a control program involving eradication of virus sources in the field, represented by infected plants in papaya orchards, abandoned orchards and infected plants identified in backyards.

Biological and serological of an isolate of squash mosaic virus and effects of mixed infection with a virus of the genus Potyvirus

O Nordeste brasileiro possui condicoes edafoclimaticas favoraveis ao cultivo do meloeiro (Cucumis melo). No entanto, diferentes problemas fitossanitarios afetam sua produtividade, destacando-se as doencas ocasionadas por virus. A presente pesquisa objetivou efetuar a caracterizacao biologica e sorologica de um isolado de Squash mosaic virus (SqMV) obtido no Ceara. Em estudos de gama de hospedeiros o virus infetou sistemicamente somente cinco especies da familia Cucurbitaceae e ocasionou lesoes locais em Chenopodium amaranticolor e C. quinoa. Estudos da infeccao mista do SqMV com virus do genero Potyvirus demonstraram efeito sinergico entre os mesmos. A purificacao quimica do SqMV foi possivel a partir de plantas de meloeiro e a imunizacao em coelho com a preparacao purificada possibilitou a producao de antissoro policlonal especifico. O antissoro produzido apresentou titulos de 1:10.000 quando avaliado por plate trapped antigen enzyme linked immune absorbent assay (PTA-ELISA), de 1:160.000 em immune-precipitation ELISA (IP-PTA-ELISA) e de 1:1.024 em Dupla Difusao em Agar. Estudos do relacionamento sorologico entre SqMV e Cowpea severe mosaic virus (CPSMV) do genero Comovirus contra seus antissoros homologos e heterologos em Dupla Difusao em Agar demonstraram relacionamento unilateral entre os mesmos.

Biological stability of a strain of Cowpea severe mosaic virus over 20 years.

Cowpea (Vigna unguiculata) is an important crop of the traditional agriculture system in the Northeast of Brazil. It can be infected by more than 20 virus species and Cowpea severe mosaic virus (CPSMV) is one of the most important pathogens that naturally infect cowpea in Brazil. Several CPSMV isolates were obtained and characterized in the Plant Virus Laboratory at the Federal University of Ceara: CPSMV-CE - the first characterized isolate of the virus obtained from cowpea in the State of Ceara; CPSMV-AL - isolated from cowpea in Alagoas; CPSMV-PE - isolated from cowpea in Pernambuco; CPSMV-PR - obtained from soybean (Glycine max) in Parana and CPSMV-CROT - isolated from Crotalaria paulinea, in Maranhao. An isolate of CPSMV with the property to infect the cv. Macaibo, a cowpea cultivar immune to most of CPSMV isolates was also biologically and serologically characterized as a new strain of the virus (CPSMV-MC). The CPSMV-MC was isolated in January 1990 and has been evaluated over 20 years by host range studies and maintenance in vivo by periodical mechanical inoculations in cowpea. The results of this periodical evaluation revealed that the biological integrity and the serological properties of CPSMV-MC were preserved over 20 years, indicating that the genetic preservation of a virus strain could occur over the years. Molecular studies involving part of the coat protein (CP) gene of CPSMV-MC and five other Brazilian CPSMV isolates indicated a high degree of conservation, with 92-100% nucleotide sequence identity among the isolates.

Sorologia e sobrevivência do vírus do amarelo letal do mamoeiro

The Papaya lethal yellowing virus (PLYV) is responsible for one of the most important disease of papaya (Carica papaya) in the Northeast of Brazil. The PLYV can be transmitted through the soil, irrigation water, agriculture tools and contaminated hands. The present research had the objective to characterize biologically, serologically and physically a PLYV isolate and evaluates how long it survives in infected dried tissues. The PLYV was identified by indirect enzyme linked immunoabsorbent assay (ELISA), isolated in young papaya plants by mechanical inoculations and maintained at green house conditions for virus purification. Approximately 309.5 mg of virus was purified per kg of infected papaya leaves and a polyclonal antiserum was obtained from an immunized rabbit. The antiserum obtained was shown to be highly specific to PLYV with a titer of 1:128 in double immune-diffusion and a titer of 1:1.024.000 in indirect ELISA. The virus was detected in dried roots and leaves maintained at room temperature up to 120 days, confirming its high stability within nonliving plant tissues, which could explain its dissemination by contaminated hands, tools, water and soil. The physical properties determined for the virus revealed a thermal inactivation point of 80 o C, longevity in vitro over 50 days and dilution end point ac. of 10 -6 .