Carlos Alexandre Zanutto

Flutuação populacional de cigarrinhas vetoras de Xylella fastidiosa Wells et al. em pomares comerciais de citros no noroeste do Paraná

The citrus variegated chlorosis (CVC), an important disease of citrus in Brazil, is caused by the bacterium Xylella fastidiosa Wells et al. and transmitted by xylem-feeding sharpshooters (Hemiptera: Cicadellidae). This study evaluated the fluctuation of populations of species of sharpshooters belonging to the tribes Cicadellini and Proconiini, from subfamily Cicadelinae, in a commercial sweet orange [Citrus sinensis (L.) Osb.] grove, located in the Northwest Region of Parana State, Brazil, in four varieties: Valencia, Natal, Pera, and Folha Murcha. Sharpshooters population was monitored using yellow stick traps sampled at 15 day-intervals, in 24 traps, from November of 1999 to March of 2004. The most abundant species were Dilobopterus costalimai Young (tribe Cicadellini) and Acrogonia citrina Marucci & Cavichioli (tribe Proconiini). Both species were detected during the complete period studied, which is important because they have great potential for transmitting CVC. Thus, since more than a sharpshooter species were detected, more efforts are recommended to monitor and control these insects in citrus groves, aiming to reduce the dissemination of CVC.

Populational fluctuation of vectors of Xylella fastidiosa, wells in sweet orange [Citrus sinensis (L.) Osbeck] varieties of northwest Paraná State, Brazil

The aim of the present study was to assess the population flutuation of the sharpshooters species subfamily Cicadellinae belonging to the tribes Cicadellini and Proconiini, in sweet orange [Citrus sinensis( L). Osbeck] commercial orchards of the northwest region of Parana State , Brazil. Samplings were carried out the employing every time 24 yellow sticky cards. Identification of the species showed that the most representative were Dilobopterus costalimai of the Cicadellini tribe and Acrogonia citrina of the Proconiini tribe.

Comparison of Citrus tristeza virus (CTV) isolates by RFLP analysis of the coat protein nucleotide sequences and by the severity of the symptoms

Plants of Pera sweet orange on Rangpur lime rootstocks, from orchards of the northwest and north of Parana state, Brazil, were evaluated for severity of symptoms and genetic diversity of Citrus tristeza virus. The severity of symptoms was evaluated by the development of tree, fruit size and stem pitting symptoms. Isolates that infect these plants were compared with known mild and severe isolates by analysis of restriction fragments length polymorphism (RFLP) of the coat protein nucleotide sequences (CPNS), amplified by the polymerase chain reaction (PCR) and undergone digestion with the restriction enzymes Hinf I and Rsa I. The severity of symptoms showed that the analyzed plants from the northwest orchards presented mild to moderate tristeza symptoms, while the plants from the north orchards exhibited moderate to severe symptoms. The RFLP analysis revealed that the CTV isolates are constituted by haplotype mixtures. Rsa I was the enzyme that best discriminated the genetic diversity among the analyzed isolates of CTV. Two main groups were generated by the UPGMA analysis. The isolates from the northwest orchards grouped with most of the mild isolates used as control, and a great part of the isolates from the north orchards, was correlated with the severe isolate Capao Bonito. Correlation between the stem pitting intensity and RFLP patterns, was demonstrated with some exceptions. The failure of protection of some isolates and the contamination of the rootstocks by the severe isolates, in field nursery conditions, before grafting with scions with mild isolates, were the hypotheses considered to explain the occurrence of severe CTV isolates in the North area of Parana State.

Biological and molecular characterization of Citrus tristeza virus isolates with potential to use in cross-protection programs.

A cross-protection program citrus tristeza disease, caused by Citrus tristeza virus (CTV) has been developed in the Parana State, to obtain Pera orange mother plants. Thus, 20 plants were selected in the orange commercial fields of the North and Northwest region. Comparisons between mild and severe recognized isolates were made. The results showed mild-to-moderate stem pitting symptoms and the great majority of the isolates grouped up with the mild control isolate. These results suggest that the plants selected were infected by CTV mild haplotypes showing that they have mother plant potential.

Caracterização morfofisiológica e identificação molecular de isolados de Guignardia citricarpa, agente patogênico da mancha preta dos citros

O presente trabalho teve como objetivo identificar 11 isolados de Guignardia citricarpa, agente causal da mancha preta dos citros (MPC), obtidos de frutas citricas sintomaticas de diferentes regioes geograficas, por meio da PC R e caracterizacao morfofisiologica das estruturas propagativas, esporulacao e crescimento micelial em diferentes meios de cultura, temperaturas e regimes de luz, nas condicoes de laboratorio. Pelo teste de PCR, todos os isolados foram identificados como o patogeno G. citricarpa. Os isolados caracterizados foram submetidos as temperaturas de 20, 25 e 30oC, em regime de luz continua, escuro continuo e fotoperiodos de 12 horas, durante 24 dias. Utilizaram-se os meios de cultura aveia-agar (AA), batata-dextrose-agar (BDA) e cenoura-dextrose-agar (CDA). Os resultados mostraram que ocorreu interacao entre os diferentes meios de cultura, temperaturas e fotoperiodos. O meio de cultura que melhor estimulou o crescimento micelial foi o CDA a 25oC sob o fotoperiodo de 12h. A maior producao de esporos (conidios) foi verificada no meio BDA a 20oC, no fotoperiodo de 12 horas. No meio CDA, nao ocorreu esporulacao de nenhum isolado. Sob a temperatura de 30oC, foi verificada apenas a producao de hifas e picnidios para a maioria dos isolados, em todos os meios de cultura e fotoperiodo testados.

Evaluation of Resistance to Asiatic Citrus Canker among Selections of Pêra Sweet Orange (Citrus sinensis)

Asiatic citrus canker (ACC, caused by the bacterium Xanthomonas citri subsp. citri) is a destructive disease of citrus in Brazil and in several other citrus-producing countries. ACC management is problematic, and bactericides such as copper can be reasonably efficacious but do not completely control the disease. Furthermore, injury by citrus leaf miner (CLM) can exacerbate severity of ACC. Host resistance is the most desirable solution for management of ACC; however, evaluations of germplasm indicate that resistance is limited in many popular species and cultivars that are grown commercially. Limited evaluations have been made of sweet orange (Citrus sinensis) selections. We evaluated resistance of 25 Pêra sweet orange selections to X. citri subsp. citri by wound inoculation and measuring lesion diameter under greenhouse conditions (wound inoculation indicates mesophyll resistance which will be valuable in areas where CLM exists). ACC severity was assessed on the same 25 selections at three locations in the field in Brazil, relying on natural inoculum and conditions to cause disease. In the greenhouse experiments, the selections EEL, Bianchi/CC, Ipiguá, Olimpia, IAC 2000/1, and Ovale Siracusa consistently had the smallest diameter lesions, indicating greatest resistance, although differences in lesion diameter were small. Results from the field experiments were less conclusive, although EEL and Ovale Siracusa were consistently numerically least affected by ACC. These results indicate selections of sweet orange that might be preferable to consider in canker-prone areas in Brazil and elsewhere.

Heterokaryosis and diploid formation among Brazilian isolates of Macrophomina phaseolina

T. S. Pereira, G. N. Machado Esquissato, C. C. da Silva Franco, P. C. de Freitas Mathias, D. J. Soares, C. H. Bock, W. M. de Carvalho Nunes, C. A. Zanutto and M. A. A. de Castro-Prado* Departamento de Biotecnologia, Gen etica e Biologia Celular, Universidade Estadual de Maring a, Avenida Colombo 5790, Maring a, PR 87020-900; Empresa Brasileira de Pesquisa Agropecu aria (Embrapa Algod~ ao), Rua Osvaldo Cruz, no. 1143, Campina Grande, PB 58428-095, Brazil; USDA-ARS-SEFTNRL, Byron, GA, USA; and Departamento de Agronomia, Universidade Estadual de Maring a, Avenida Colombo 5790, Maring a, PR 87020-900, Brazil

Reaction of detached leaves from different varieties of sweet orange to inoculation with Xanthomonas citri subsp. citri

Citrus genotypes show a broad range of resistance to infection with Xanthomonas citri subsp citri (Xcc), the causal agent of Asiatic citrus canker (ACC). The aim of this study was to evaluate a detached leaf inoculation method to compare nine different citrus genotypes that exhibit varied resistance levels to ACC, and to evaluate infection, colonization and symptom development of the varieties by using Scanning Electron Microscopy (SEM). Inoculation of Xcc in the leaves was carried out by producing injuries with needles. Lesion diameters were measured at 7, 10 and 13 days after inoculation (DAI). The variety Pera IAC was most resistant to the pathogen and had lesions with smaller diameters, while the variety Washington was most susceptible and had the largest lesions, indicating low resistance to Xcc. SEM images were taken from the lesion development, and sections were obtained from the disease lesions in the tested varieties. The most resistant variety, Pera IAC, had smaller stomatal openings and produced greater quantity of foliar exudates, compared with the variety Washington. We hypothesize that the exudates may contain Xcc toxic compounds and thus may be a defense mechanism against infection by Xcc, but further research is required to establish any antibiotic effects of the exudates against citrus canker.

Monitoramento populacional das cigarrinhas vetoras de Xylella fastidiosa, através de armadilhas adesivas amarelas em pomares comerciais de citros

A Clorose variegada dos citros (CVC) e uma doenca causada pela bacteria de xilema Xylella fastidiosa Wells. A disseminacao ocorre por meio de insetos vetores pertencente a ordem Hemiptera, familia Cicadellidae (subfamilia Cicadellinae), os quais transmitem a bacteria depois de se alimentarem em plantas contaminadas. Neste trabalho, objetivou-se identificar e monitorar as especies de cigarrinhas vetoras em um pomar comercial no municipio de Paranavai, Parana. O experimento foi realizado em um talhao comercial de laranja doce (Citrus sinensis (L.) Osbeck), variedade Pera, com 1.000 plantas de dez anos de idade. A amostragem foi realizada por meio de armadilhas adesivas amarelas, distribuidas na area periferica e central do pomar, com duas repeticoes por rua amostrada. As etiquetas foram distribuidas entre a 5a e 30a plantas em 10 ruas, totalizando 20 armadilhas que foram renovadas no pomar, a cada trinta dias, durante o periodo de avaliacao que foi entre junho de 2005 e setembro de 2006. As principais especies de Cicadellinae capturadas foram Acrogonia citrina Marucci & Cavichioli, Dilobopterus costalimai Young e Macugonalia cavifrons Stal. Essas especies apresentaram ocorrencia constante e frequencia de 3,97%, 4,2%, 13,0% respectivamente, em relacao ao total de cigarrinhas coletadas.

Ocorrência de pinta preta, causada por Guignardia citricarpa, em tangerineiras 'Montenegrina' no sul do Paraná

(McAlp.)van der Aa.], foi registrada no Brasil pela primeira vez em1980, no Rio de Janeiro, afetando pomares comerciais demexerica do ‘Rio’, nos municipios de Sao Goncalo e Itaborai,na baixada fluminense. Em Sao Paulo a doenca foi constatadanos municipios de Conchal e Engenheiro Coelho, em 1992,afetando limoeiros e laranjeiras doces. No Rio Grande do Sula doenca foi constatada em 1986 afetando tangerineiras‘Montenegrina’, no vale do Rio Cai.Em amostras de tangerinas ‘Montenegrina’ (