CARACTERIZAÃÃO PATOGÃNICA E MOLECULAR DE ISOLADOS DO Potato virus Y (PVY) CAUSADORES DE ANÃIS NECRÃTICOS EM TUBÃRCULOS DE BATATA / Characterization pathogenic and molecular the isolates of Potato virus Y (PVY) causes of rings necrotics in tuber potato.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

Fourteen isolates of PVYNTN, collected at potato production fields in Brazil, were studied. Thirteen of them were from the South region of Minas Gerais and the other one was from SÃo Paulo State. All isolates were submitted to the test DAS-ELISA and RT-PCR for initial identification. After that, they were inoculated in fourteen host species for evaluation of symptoms. In addition to that, a genomic fragment of 866 pb, containing the coat protein gene, was amplified, sequenced and analyzed. A Comparative study was performed first among the Brazilian isolates and second among the Brazilian isolates and 4 PVYN and 12 PVYNTN isolates from the GenBank. All the isolates studied were ELISA positive when using the polyclonal antiserum for PVY. In the identification by RT-PCR, the discrimination among PVYN and PVYNTN isolates was successfully achieved when a mixture of primers was used. Therefore, one 280pb band for the first and another 609 pb band for the second were obtained. The plants of C. quinoa, C. amaranticolor, D. stramonium and G. globosa and Capsicum anuum cv. Florida VR2 did not present symptoms when inoculated with all isolates and they were also ELISA negative. The Capsicum anuum plants, cvs. Yolo Y and Bastidon, presented symptoms of mosaic but the severity varied with the isolates. The tobacco plants, cvs. White Burley, Turkish and Turkish NN, were highly susceptible and reacted with severe mosaic, vein necrosis, necrotic local lesion, leaf distortion, wrinkling and stunting. However, those symptoms were more severe in plants inoculated with isolates MF-AST, MUZ-AGA, PA-AGA2 and SP-MON and less severe in plants inoculated with AN-AGA, ES-AGA, LA-MON and GO-AST. The other isolates induced intermediate symptoms. Tobacco plants were considered the best hosts for the distinction among the isolates pathogenicity. The multiple alignments showed that the nucleotide identity among the studied PVY isolates varied from 93% to 100%, and the identity of amino acids varied from 90% to 100%. In the comparison among those and the other isolates from GenBank, the nucleotides identity varied from 92% to 99% and the amino acids identity ranged from 90% to 99%. It showed a low variability among them. When both phylogenetic trees, based on nucleotide and amino acid sequences, were analyzed, the isolate SGS-MO, which showed the smallest identities, did not cluster with any PVY isolate, from Brazil or from GenBank. The isolate MU-AGA, in both trees, grouped with the isolate AJ390296, from United States, indicating a probable common geographical origin. The others, excluding the IP-MAR, BR-AGA and LA-MON, presented a closer proximity. The isolates that caused more severe symptoms in tobacco plants were grouped with the ones that caused weak symptoms, indicating that the coat protein sequence probably is not related to the symptoms severity showed by the infected plant.

ASSUNTO(S)

fitopatologia

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