Molecular identification of maize bushy stunt phytoplasm strains collected in São Paulo State. / Identificação molecular de isolados do fitoplasma do enfezamento vermelho do milho coletados no Estado de São Paulo.

AUTOR(ES)

Luciana Bianchini

DATA DE PUBLICAÇÃO

2002

RESUMO

Since the middle 80s, an increase in year round cropping of maize resulted in a spread of secondary diseases in the crop’s major production areas. In this context, maize busy stunt, firstly appointed in Brazil in 1970, is occurring more frequently, often with total damage of production. Infected plants show a complex symptomatology, easily confounded with virus-caused diseases. The most characteristic symptom is leaf reddening. Besides the reddening diseased plants show stunting, often developing tillering. This disease is caused by a phytoplasma, a wall- less prokaryote, uncultivable, phloem inhabitant. This pathogen is transmitted by the leafhopper Dalbulus maidis, a in persistent and propagative manner. Due to the pathogen’s characteristics, the best control measure is the use of tolerant/resistant plants. For efficiency in breeding, accurate procedures of detection and an investigation of the pathogen’s genetic variability are necessary. The more accurate manner is using PCR. PCR, using 16SrDNA based primers pairs and followed by RFLP analysis, offers a safe identification of the pathogen. Today the phytoplasma classification is based in molecular patterns obtained by RFLP analysis of amplified 16SrDNA gene fragments. This work’s objective was the molecular characterization of maize bushy stunt phytoplasma strains collected in four corn production areas in São Paulo state, Brazil. The simptomatology to every maize sample was saved. Two primer pairs in nested PCR and a specific primer pair developed to MBS detection were used, besides group specific phytoplasma primers pairs. After amplification and electrophoresis, 29 samples were selected. These selected samples were digested with different restriction enzymes to identify/classify the phytoplasma. The fragment’s sizes obtained by electrophoresis through 4,5% polyacrilamide gel were compared with the reference’s classification patterns. All analyzed samples showed identical fragment-size patterns, for each restriction enzyme considered individually. There was no difference between these samples according to geographic collect region or according to symptoms. All strains were identified as belonging to group I and subgroup B of molecular classification.

ASSUNTO(S)

doenças de plantas corn mycoplasma phytoplasm plant disease milho

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