Caracterização molecular e análise da variabilidade genética do Papaya lethal yellowing virus (PLYV), e triagem de fontes de resistência ao vírus em germoplasma de Carica papaya L.

• Ano de defesa: 2011
• Autor(a) principal: Pereira, álvaro Julio
• Orientador(a): Zerbini Júnior, Francisco Murilo
• Banca de defesa: Andrade, Eduardo Chumbinho de , Barros, Danielle Ribeiro de , Zerbini, Poliane Alfenas
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Doutorado em Genética e Melhoramento
• Departamento: Genética animal; Genética molecular e de microrganismos; Genética quantitativa; Genética vegetal; Me
• País: BR
• Palavras-chave em Português: Carica papaya; PLYV; Caracterização molecular; Diversidade genética; Resistência genética
• Palavras-chave em Inglês: Carica papaya; PLYV; Molecular characterization; Genetic diversity; Genetic resistance
• Área do conhecimento CNPq: CNPQ::CIENCIAS BIOLOGICAS::GENETICA::GENETICA MOLECULAR E DE MICROORGANISMOS
• Link de acesso: http://locus.ufv.br/handle/123456789/1335

The papaya (Carica papaya L.) is a fruit crop of great economical importance throughout the Brazilian northeast, which is responsible for 60% of the national output. Papayas in the states of Ceará and Rio Grande do Norte are affected by lethal yellowing disease, caused by Papaya lethal yellowing virus (PLYV). To assess the genetic variability of PLYV isolates, foliar samples were collected in fields from Ceará and Rio Grande do Norte states. Fragments from 16 viral isolates with approximately 900 bp were RT-PCR-amplified, cloned and sequenced. Sequence analyses indicated >97% identity among the isolates, 94-100% identity with a previously sequenced PLYV isolate, and a lower but significant identity with viruses in the genus Sobemovirus. These results indicate a low degree of genetic variability among PLYV isolates. The viral genome was sequenced in its entirety using the Roche 454 GS-FLX Titanium platform. Sequence analysis indicates the presence of a first ORF with the potential to encode a protein without any significant similarity with known proteins, two partially overlapping ORFs that potentially encode an RNA-dependent RNA polymerase, and a fourth ORF which potentially encodes the coat protein. The RdRp and CP have significant sequence identity with sobemoviruses. In spite of the lack of sequence similarity of ORF1, the nearly identical genomic organization with sobemoviruses, including a putative frame shift site between the two ORFs which encode the RdRp, as well as the identity of the RdRp and CP ORFs, confirm the classification of PLYV as a species in the genus Sobemovirus. With the objective of evaluating the existence of genetic resistance to PLYV in papaya germplasm, a study was conducted with 60 accessions from the BAG (Active Germplasm Bank) of Embrapa Mandioca e Fruticultura. The plants were mechanically inoculated in a completely randomized design. Inoculated plants were tested for viral infection 90 days after inoculation by indirect ELISA using a polyclonal antiserum against PLYV. The results indicate that accesses CMF11, 15, 20, 21, 22, 26, 30, 33, 36, 38, 44, 47, 52, 54, 60, 72, 76, 82, 88, 92, 94, 102, 108, 114, 116, 120, 121, 123, 129, 130, 132, 150, 155, 166, 172, 175, 176, 183,186, 200, 204, 206, 220, 223, 230, 233, 234 and 235 are possible sources of resistance to the virus. In case these results are confimed, these accesses can be used in breeding programs aiming at incorporating resistance to lethal yellowing in commercial papaya cultivars.