Diversidade genÃtica de isolados de Spiroplasma kunkelii e reaÃÃes em genÃtipos de milho / Genetic Diversity of Spiroplasma kunkelii strains and their reactions in maize genotypes

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

The microorganism Spiroplasma kunkelii causes the Corn Stunt Disease. The study of the pathogen and the characterization of its genetic variability is important to stablish a breeding program for resistance. The objectives of this study were to analyze the genetic diversity between geographical strains of S. kunkelii and their reaction in different maize genotypes. The strains were acquired from four brazilian regions: Dourados (MS), Itumbiara (GO), Sete Lagoas (MG) e UberlÃndia (MG). The strains were cultivated in vivo, in susceptible maize plants, and also in vitro, using LD8A3 medium. The strains cultivated in vitro showed a slow growth, taking between 17 and 20 weeks, although it was possible to detect spiroplasmas in 11 weeks old media, using the Western Blott technique. The strains cultivated in vivo were used to inoculate four maize lines and for hybrids. Plants infected by spiroplasma showed significant reduction in development and in the translocation of nutrients, such as Mg, Ca, S, and Fe, from the vegetative parts to the grains. The genetic variability was studied at molecular level, using AFLP and RFLP molecular markers. For the AFLP analysis, 10 primers combinations were used and 448 bands were obtained. However, the polymorphism was low, about 26,6%. The results indicated low genetic diversity between strains. The genetic diversity among among the strains was 8-fold higher than between them. For the RFLP analysis a part of the spiralin gene was used as the molecular marker. Five restriction enzymes, DraI, HinfI, MseI, XmnI e BamHI were used.No polymorphism was found with the above restriction enzymes. This result confirms that the spiralin gene is a highly conserved site at spiroplasma genome, and is not a good marker for genetic diversity analysis among spiroplasma strains

ASSUNTO(S)

melhoramento vegetal spiroplasma enfezamento diversidade genÃtica espiroplasma corn stunt genotype genÃtipo maize diversity genetic milho

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