Detecção e identificação molecular de um fitoplasma do grupo 16SrIII em plantas de maçã com sintomas de lenho mole. / Detection and molecular identification of a phytoplasma of the group 16sriii in apple plants with rubbery wood symptoms.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

The proliferation and rubbery wood diseases which are associated with phytoplasma are some of the diseases that occur in apple trees (Malus spp). In the case of rubbery wood disease, phytoplasm is not totally accepted as its causal agent. However, several researches by using electron microscopy and tissue grafting, have been able to show the phytoplasma associated with that disease. Recently, a phytoplasma from group 16SrI was detected in apple plants grown in Canada and Czech Republic. In Brazil, rubbery wood occurs in several states of the south region. Results obtained through electron microscopy and transmission biological tests using grafiting have shown a possible phytoplasma associated to the disease. The purpose of the present work was to contribute for the knowledge of that disease aetiology. Thus tissue samples from three apple plants exhibiting rubbery wood symptoms, grown at an orchard installed in the region of Vacaria/RS, were obtaind for phytoplasma detection, identification and classification. Nested PCR technique with R16mF2/mR1 and R16F2n/R2 primers was emploed to detect phytoplasma. PCR with R16(III) F2/R1 primers and RFLP technique with the restriction enzymes Alu I, Hha I, Kpn I, Hinf I, Hpa II, Mse I, Rsa I and Sau 3AI were used to phytoplasma indentification. The results showed that phytoplasma occurred in 29 of the 54 samples collected in the year of 2000. Branches and root samples obtained from January to April and from September to October exhibited phytoplasma in their tissues. In tissue samples collected from June to August, the microorganism has not been detected. The molecular identification revealed that the phytoplasm from symptomatic plants belonged to the group 16SrIII and the PCR results were confirmed by RFLP technique. Based upon the RFLP analyses it can be suggested that this phyoplasma is a member of the sub-group B. The occurrence of a phytoplasm of group 16SrIII associated to rubbery wood in apple plants grown in Brazil, reinforces the evidences related in other works, that a phytoplasm is the causal agent of that disease. The fact that a phytoplasm diferent from 16SrI group is associated to rubbery wood diseases in Brazil can be justified for the diversity of these mollicutes, due to geographical area and host.

ASSUNTO(S)

maçã phythoplasma poliferation fitoplasma apple rubbery wood superbrotamento lenho mole

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