7 research outputs found

    Resposta diferencial de espécies e de híbridos de citros à leprose Differential response of citrus species and hybrids to leprosis

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    O objetivo deste trabalho foi buscar novas fontes de resistĂȘncia Ă  leprose-dos-citros, no Banco Ativo de Germoplasma do Centro APTA Citros Sylvio Moreira, Instituto AgronĂŽmico, em CordeirĂłpolis, SP. Foram utilizadas plantas obtidas por sementes de 26 acessos, infectadas com o vĂ­rus da leprose-dos-citros (Citrus leprosis virus - CiLV), por meio do seu vetor Brevipalpus phoenicis. O aparecimento de lesĂ”es, a partir de 21 dias apĂłs a inoculação, foi observado em 11 dos genĂłtipos testados (42,3%). Quinze espĂ©cies, entre elas Citrus pennivesiculata e C. celebica, comportaram-se como altamente resistentes, enquanto outras, como C. keraji, foram mais suscetĂ­veis que o padrĂŁo C. sinensis. Os dados mostraram grande variação de respostas de Citrus spp. Ă  leprose, com elevado nĂșmero de espĂ©cies resisentes, que podem ser utilizadas como fonte de resistĂȘncia Ă  doença em programas de melhoramento.<br>The objective of this work was to prospect for new sources of resistance to leprosis in the Citrus Germplasm Bank of Centro APTA Citros Sylvio Moreira, Instituto AgronĂŽmico, in CordeirĂłpolis, SP, Brazil. Plants obtained through seeds from 26 citrus accessions were mite-infected with Citrus leprosis virus (CiLV). Typical lesions started to appear in 11 genotypes (42.3% of the tested accessions) 21 days after inoculation. Fifteen species, among them Citrus pennivesiculata and C. celebica, behaved as highly resistant, while other genotypes, as C. keraji, were more susceptible than the standard C. sinensis. The data showed a wide variation in the response of Citrus spp. to leprosis, with a large number of resistant species, wich can be used as source of resistance to this disease, in breeding programs

    Caracterização de um vírus baciliforme isolado de Solanum violaefolium transmitido pelos åcaros Brevipalpus phoenicis e Brevipalpus obovatus (Acari: Tenuipalpidae) Characterization of a bacilliform virus isolated from Solanum violaefolium transmitted by the tenuipalpid mites Brevipalpus phoenicis and Brevipalpus obovatus

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    Solano-violeta (Solanum violaefolium) Ă© uma planta ornamental rasteira usada para cobrir solos de ĂĄreas sombreadas. Um vĂ­rus que induz manchas anelares nas folhas desta planta, tentativamente designado Solanum violaefolium ringspot virus - SvRSV, transmitido pelo ĂĄcaro Brevipalpus phoenicis (Acari: Tenuipalpidae) foi encontrado em Piracicaba, SP. Trata-se de um vĂ­rus baciliforme que se assemelha a outros vĂ­rus do tipo citoplasmĂĄtico transmitidos por Brevipalpus sp. Este trabalho teve como objetivo relatar propriedades biolĂłgicas e estabelecer uma caracterização molecular parcial do SvRSV. O vĂ­rus pode ser transmitido mecanicamente a vĂĄrias outras espĂ©cies botĂąnicas, causando lesĂ”es localizadas. Entre as espĂ©cies avaliadas, Datura stramonium mostrou-se a melhor hospedeira experimental. Observou-se tambĂ©m a manifestação de sintomas nestas plantas apĂłs infestação das mesmas por B. obovatus previamente alimentado em lesĂ”es de SvRSV, confirmando esta outra espĂ©cie de ĂĄcaro como vetor do vĂ­rus. Suas propriedades fĂ­sicas in vitro foram: temperatura de inativação 40-45 ÂșC; ponto final de diluição 10-3-10-4; longevidade in vitro 12 dias. Em secçÔes ultrafinas, as partĂ­culas do SvRSV mostraram-se levemente mais delgadas e mais longas que as de outros vĂ­rus do mesmo grupo. A partir do dsRNA do SvRSV foi construĂ­da uma biblioteca de cDNA e foram identificadas duas possĂ­veis regiĂ”es codificadoras das proteĂ­nas de movimento e replicase viral. Baseado nestas regiĂ”es foram desenhados "primers" para amplificação do RNA do SvRSV por RT-PCR. Sondas baseadas nas seqĂŒĂȘncias obtidas hibridizaram com ss- e dsRNA de D. stramonium infectadas pelo vĂ­rus. Ensaios preliminares de RT-PCR e hibridização nĂŁo resultaram em reação com o vĂ­rus da leprose dos citros, tipo citoplasmĂĄtico (CiLV-C).<br>Solanum violaefolium is an ornamental plant, with prostrate, trailing growth habit and is cultivated in shaded areas. A virus that causes ringspot symptoms on its leaves, tentatively named as Solanum violaefolium ringspot virus (SvRSV) and transmitted by Brevipalpus phoenicis (Acari: Tenuipalpidae) was found in Piracicaba city, SĂŁo Paulo State. It is a bacilliform virus that resembles other cytoplasmic viruses transmitted by Brevipalpus sp. The objective of this work is to describe the biological properties and establish partial molecular characterization of the SvRSV. The SvRSV can be transmitted mechanically to several plant species causing local lesions. Among the tested species, Datura stramonium was proved to be the best experimental host. It was observed that S. violaefolium plants were infested by B. obovatus that also transmitted SvRSV in preliminary assays. Its in vitro physical properties were: thermal inactivation point: 40-45 ÂșC; dilution end point: 10-3-10-4 and in vitro longevity: 12 days. Ultrathin sections revealed that SvRSV particles are slightly thinner and longer than other cytoplasmic-type viruses transmitted by Brevipalpus sp. A cDNA library from dsRNA molecules extracted from SvRSV was constructed and two regions, which putatively code for the replicase and movement proteins were identified. Based on these sequences, primer pairs were designed for SvRSV&acute;s RNA amplification by RT-PCR. Indeed, probes based on such sequences hybridized with ss- and dsRNA from infected D. stramonium plants. Preliminary molecular assays using primers and probes of SvRSV did not detect Citrus leprosis virus, cytoplasmic type (CiLV-C), another cytoplasmic type Brevipalpus-transmitted viruses

    The citrus leprosis pathosystem O patossistema leprose dos citros

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    Citrus leprosis is considered the main viral disease for the Brazilian citrus production, particularly for the State of SĂŁo Paulo, due to the high costs spent for the chemical control of its vector, the tenuipalpid mite Brevipalpus phoenicis. In addition, its global importance has significantly increased in the last years, with the dissemination of the virus to new countries in South and Central America. In Brazil, despite its economical importance and occurrence for more than seven decades, the most significant advances towards understanding the pathosystem interactions have been obtained only in the last ten years. This review focuses on various aspects of the disease, beginning with a historical view, its main characteristics, alternatives for its control, its increasing economical importance in Brazil and abroad, and the new data on the search for understanding the interactions amongst the mite vector, the virus, and the plant host.<br>A leprose dos citros Ă© considerada a principal virose na citricultura brasileira, com maior destaque no Estado de SĂŁo Paulo, principalmente pelos altos custos demandados para o controle quĂ­mico do vetor, o ĂĄcaro Brevipalpus phoenicis. AlĂ©m da relevĂąncia dessa virose para a citricultura local, sua importĂąncia mundial vem sendo ampliada consideravelmente nos Ășltimos anos, principalmente com a disseminação do vĂ­rus em novos paĂ­ses da AmĂ©rica do Sul e Central. No Brasil, apesar da sua importĂąncia econĂŽmica e ocorrĂȘncia por mais de sete dĂ©cadas, os mais importantes avanços no entendimento das interaçÔes do patossistema leprose tĂȘm sido obtidos apenas nos Ășltimos dez anos. Essa revisĂŁo aborda os diferentes aspectos dessa doença, trazendo um breve histĂłrico da doença, principais caracterĂ­sticas da leprose, alternativas de controle, sua crescente importĂąncia econĂŽmica na cadeia citrĂ­cola nacional, os mais recentes relatos de sua ocorrĂȘncia em outros paĂ­ses e os novos resultados obtidos pela pesquisa buscando um melhor entendimento das interaçÔes entre ĂĄcaro, vĂ­rus e hospedeiro vegetal

    Breeding, genetic and genomic of citrus for disease resistance

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    Although the citriculture is one of the most important economic activities in Brazil, it is based on a small number of varieties. This fact has contributed for the vulnerability of the culture regarding the phytosanitary problems. A higher number of varieties/genotypes with potential for commercial growing, either for the industry or fresh market, has been one of the main objectives of citrus breeding programs. The genetic breeding of citrus has improved, in the last decades, due to the possibility of an association between biotechnological tools and classical methods of breeding. The use of molecular markers for early selection of zygotic seedlings from controlled crosses resulted in the possibility of selection of a high number of new combination and, as a consequence, the establishment of a great number of hybrids in field experiments. The faster new tools are incorporated in the program, the faster is possibility to reach new genotypes that can be tested as a new variety. Good traits should be kept or incorporate, whereas bad traits have to be excluded or minimized in the new genotype. Scion and rootstock can not be considered separately, and graft compatibility, fruit quality and productivity are essential traits to be evaluated in the last stages of the program. The mapping of QTLs has favored breeding programs of several perennial species and in citrus it was possible to map several characteristics with qualitative and quantitative inheritance. The existence of linkage maps and QTLs already mapped, the development of EST and BAC library and the sequencing of the Citrus complete genome altogether make very demanding and urgent the exploration of such data to launch a wider genetic study of citrus. The rising of information on genome of several organisms has opened new approaches looking for integration between breeding, genetic and genome. Genome assisted selection (GAS) involves more than gene or complete genome sequencing and is becoming an import support in breeding programs of annual and perennial species. An huge information amount can be derivate from genome analysis. The use and benefit of such informations will depend on the genetic basis of the breeding program
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