Estudo de isolados brasileiros de potyvírus causadores de endurecimento dos frutos do maracujazeiro e análise da resistência à doença em linhagens transgênicas R1 de maracujá-amarelo

• Ano de defesa: 2006
• Autor(a) principal: Nascimento, Ana Verônica Silva do
• Orientador(a): Zerbini Júnior, Francisco Murilo
• Banca de defesa: Pio-ribeiro, Gilvan , Zerbini, Poliane Alfenas , Oliveira, Rosângela D arc de Lima
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Doutorado em Fitopatologia
• Departamento: Etiologia; Epidemiologia; Controle
• País: BR
• Palavras-chave em Português: Maracujá; Potyvirus; Plantas transgênicas
• Palavras-chave em Inglês: Passionfruit; Potyvirus; Transgenic plants
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOSSANIDADE::FITOPATOLOGIA
• Link de acesso: http://locus.ufv.br/handle/123456789/1040

Passionfruit woodiness is the most important disease of passion flower. The disease can be caused by the potyviruses Passionfruit woodiness virus (PWV), Cowpea aphid-borne mosaic virus (CABMV) and East Asian Passiflora virus (EAPV). Infected plants display mosaic and woodiness of the fruit. In Brazil, the disease occurs in all states where passion flower is grown, and the causeal agent has always been identified as PWV based on biological and serological properties. Management strategies based on vector control with insecticides, cross-protection and natural resistance are inneficient. The objectives of this work were to characterize at the molecular level a number of Brazilian isolates of potyvirus causing passionfruit woodiness and to evaluate the resistance of transgenic yellow passion flower (Passiflora edulis f. flavicarpa) plants expressing a genomic fragment from a woodinessinducing potyvirus isolate from Brazil. Foliar samples of yellow passion flower showing typical symptoms of the disease were collected collected in the states of Bahia, Espírito Santo, Minas Gerais, Paraíba, Pernambuco and Sergipe. The presence of the virus was confirmed by serology and host range. The viral isolates were capable of infecting plants of common bean and cowpea, although differing in the intensity of symptoms induced in these hosts. Serological relationship between the potyvirus isolates from passion flower Cowpea aphidborne mosaic virus (CABMV) was demonstrated by indirect ELISA. The sequence of the capsid protein coding region was determined for all isolates. Sequence comparisons with other potyviruses indicated a level of identify from 85 to 94% with CABMV isolates. Identity with PWV isolate K ranged from 54 to 70%. Phylogenetic analysis based on the deduced capsid protein amino acid sequences clustered the Brazilian isolates together with CABMV isolates, distant from PWV isolates. Together, these results indicated that the potyvirus isolates from passion flower represent a strain of CABMV. In an attempt to effectively control passionfruit woodiness, transgenic yellow passionfruit plants (Passiflora edulis f. flavicarpa) were generated which express an untranslatable RNA corresponding to the replicase and capsid protein coding regions of a CABMV isolate from Minas Gerais (MGAvr). One R0 plant (TE5-10) was resistant to the MG-Avr isolate due to RNA silencing. However, this plant was susceptible to a second isolate of the virus (PE-Bnt). In order to verify the effect of gene dosage in the spectrum of resistance, several crosses were carried out between the TE5-10 plant, a susceptible R0 plant (T2-5) ans a non-transformed plant. Also, self-pollination of the TE5-10 plant was carried out in orde to generate transgene-homozigous R1 plants. The plants obtained from these crosses were challenged with three CABMV isolates (MG-Avr, PE-Bnt and SE-Nps). One R1 plant obtained from self-pollination (named TE5-10-15J) was resistant to the three isolates. This plant was challenged with an additional four CABMV isolates (PB-Alh, BA-Itb, ES-Vni and PA-Iga), being resistant to all of them based on symptom development. Northern analysis demonstrated the lack of transgenic mRNA accumulation in these plants, indicating that resistance is due to RNA silencing.