Passion fruit proliferation phytoplasma: molecular identification, phylogenetic analysis and proof of pathogenicity / Fitoplasma do superbrotamento do maracujazeiro: identificação molecular, análise filogenética e prova de patogenicidade

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

Phytoplasmas are cell wall-less prokaryotes and phloem-inhabitants associated with diseases that affect several crops. Passion fruit plant is a tropical species cultivated in various Brazilian regions. Diseases are among factors that may cause damage to this crop and the passion fruit witchesbroom has been revealed as very important one. That disease, associated with phytoplasma, was reported only in Brazil, where it was registered in Rio de Janeiro and Pernambuco States in the beginning of eighty decade. Although some studies about that subject have been made previously, the present study was conducted in order to: demonstrate the constant presence of the agent in association with diseased plants; reveal the occurrence of fitoplasma in some areas belonging to some States; identify, classify and study phylogenetically the phytoplasma; and demonstrate the pathogenicity of passion fruit witchesbroom phytoplasma. In 2005-2006, symptomatic plants suspected of phytoplasma infection were sampled in some areas of São Paulo State and various other Brazilian States. The detection and identification by nested PCR were performed with the universal primer pair R16mF2/mR1-16F2n/R2 and specific pair R16(III)F2/R1, respectively. For RFLP analyses were used the restriction enzymes AluI, HhaI, KpnI, HinfI, HpaII, MseI, RsaI e MboI. Phylogenetic analyses were based on the nucleotide sequences of the 16S rDNA from phytoplasmas belonging to distinct groups and subgroups. Pathogenecity assays were made by using grafting of tissue. Amplifications of DNA fragments of 1.2kb by using universal primer pairs revealed the presence of phytoplasma in the symptomatic plants from all sampled regions. Amplifications of DNA fragments of 0,8kb by specific primer pair indicated that the detected phytoplasma is affiliated to the group 16SrIII, while RFLP analyses confirmed the identification based on PCR and showed that phytoplasma may be classify as a member of the subgroup 16SRIII-B. Sequencing and phylogenetic analysis revealed that the passion fruit witchesbroom phytoplasma is a typical representative of group 16SRIII, when compared with phytoplasmas from other groups. Pathogenicity was demonstrated through the observation of typical symptoms of the disease followed by molecular detection of the phytoplasma in healthy plants grafted with shoots from infected plants. The results obtained in the present study allowed: to confirm the diagnosis based on the symptomatology; to reveal the firm association between diseased plant and phytoplasma, confirming previous investigations conduced by electron microscopy; to identify the phytoplasma as a member of the group 16SRIII-B; to demonstrate that phytoplasma is the causal agent of passion fruit witchesbroom; and to show the present occurrence of the pathogen in the States of Bahia, Paraná, Rio de Janeiro, Sergipe, and São Paulo

ASSUNTO(S)

maracujá - técnicas moleculares passion fruit superbrotamento. witchesbroom phythoplasma mollicutes. fitoplasmas

ACESSO AO ARTIGO

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