Analyses of DNA polymorphism and virulence variation were used to evaluate the population structure of Xanthomonas axonopodis pv. manihotis, the pathogen causing cassava bacterial blight in Colombia. We collected strains from the major cassava-growing regions which can be grouped into different edaphoclimatic zones (ECZs) according to environmental conditions, production constraints, and economic parameters. DNA polymorphism was assessed by a restriction fragment length polymorphism analysis, using an X. axonopodis pv. manihotis plasmid DNA sequence (pthB) as a probe to evaluate the genetic relatedness among 189 Colombian strains. The sampling intensity permitted the estimation of genetic differentiation within and among ECZs, sites, and fields and even within an individual plant. A multiple correspondence analysis indicated that the Colombian X. axonopodis pv. manihotis population showed a high degree of diversity relative to X. axonopodis pv. manihotis populations studied previously, and the entire collection was grouped into seven clusters. A general correlation was observed between the clusters and the geographical origin of the strains, as each cluster was largely composed of strains from the same ECZ. Representative strains, identified with pthB, were further characterized by ribotyping, hybridization to two repetitive genomic probes (pBS6 and pBS8), and restriction analysis of plasmid contents to evaluate the complementarity of these markers. Virulence variation was observed within the Colombian collection. Strains of different aggressiveness were found in all ecological zones, but no correlation between virulence variation and DNA polymorphism was observed. The genetic and virulence analyses contribute to understanding the X. axonopodis pv. manihotis population structure in Colombia.

译文

DNA多态性和毒力变异分析用于评估黄单胞菌pv的种群结构。manihotis,在哥伦比亚引起木薯细菌性枯萎病的病原体。我们从主要的木薯种植区收集了菌株,根据环境条件,生产限制和经济参数,可以将其分为不同的地势区 (ecz)。使用X. axonopodis pv通过限制性片段长度多态性分析评估DNA多态性。manihotis质粒DNA序列 (pthB) 作为探针评估189哥伦比亚菌株之间的遗传相关性。采样强度允许估计ecz,地点和田地之间,甚至单个植物内部和之间的遗传分化。多重对应分析表明哥伦比亚X. axonopodis pv。相对于X. axonopodis pv,manihotis种群显示出高度的多样性。以前研究过manihotis种群,整个集合分为七个集群。在簇与菌株的地理来源之间观察到一般相关性,因为每个簇主要由来自同一ECZ的菌株组成。用pthB鉴定的代表性菌株通过核型,与两个重复基因组探针 (pBS6和pBS8) 杂交以及质粒含量的限制性分析进一步表征,以评估这些标记的互补性。在哥伦比亚的收藏中观察到毒力变化。在所有生态区均发现了具有不同侵袭性的菌株,但未观察到毒力变异与DNA多态性之间的相关性。遗传和毒力分析有助于理解X. axonopodis pv。哥伦比亚的manihotis人口结构。

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