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首页> 外文学位 >The impacts of black shank resistance management on the population biology of Phytophthora nicotianae in tobacco.
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The impacts of black shank resistance management on the population biology of Phytophthora nicotianae in tobacco.

机译：黑胫病抗性管理对烟草疫霉菌种群生物学的影响。

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摘要

Black shank of tobacco, caused by the oomycete Phytophthora nicotianae , is an important disease of tobacco. Emergence of race 1 has led to loss of major gene resistance and to questions on the genetic diversity in the pathogen in North Carolina. Race 3 is reported for the first time in NC. Race 3 is virulent on plants with the Phl gene and not the Php gene and causes severe disease symptoms on mature plants. Isolates of race 3 were recovered from locations where the Phl gene was deployed and in fields characterized as the wild-type race, race 0, with no history of single-gene resistance. In order to determine whether races 1 and 3 can develop as natural variants from race 0, and to track loss of Php and Phl virulence in races 1 and race 3, soil was infested with one race of P. nicotianae and planted with tobacco varieties with multigenic resistance. Isolates were recovered after five months and screened for race. Additionally, zoospore isolates were derived from progenitor zoospore isolates representing the three races. Zoospore progeny were screened to identify changes in virulence during asexual sporulation. A subset of zoospore progeny was subjected to Fluorescent Amplified Fragment Length Polymorphism analysis to investigate genetic diversity generated through clonal sporulation. Results showed a gain and/or loss of virulence within all race progeny in soil and single-zoospore isolates. Race 1 was the most stable phenotype, with 91% in infested soil and 99.7% of the zoospore progeny retaining the virulence phenotype. The race structure in soil infested with races 0 and 3 were similar after five months. Races were recovered in a 2:1 ratio (race 0: race 3) with a small percentage of race 1. Races 0 and 3 zoospore progeny also segregated. Race 0 progeny were 67% race 0 and 33% gained virulence to the Phl gene (race 3). Similarly, 68% of the race 3-derived progeny retained the parental virulent phenotype, 31% lost the virulent phenotype (race 0), and 1% gained virulence to the Php gene (race 1). Estimates of genetic diversity within each group of related zoospores ranged from 0.17013 to 0.44196. Phenotypic and genotypic investigations revealed that asexual sporulation may be a major source of variation in natural populations. A state-wide survey of P. nicotianae populations was conducted in NC tobacco-producing regions. Isolates were obtained from 76 tobacco fields in 23 counties and screened for race and mating type. Race 1 was predominant in most regions, with 59% of fields consisting of 90 to 100% race 1. The occurrence of race 1 within fields was positively correlated with the history of monogenic resistance deployment. Race 3 was identified in low frequency throughout the state, primarily in wild-type populations where no monogenic resistance was deployed. The A1 and A2 mating types were found throughout NC and were recovered concurrently from multiple fields. Pairings of isolates from within fields yielded viable oospores, indicating for the first time, the potential for sexual reproduction by P. nicotianae. A subset of the survey isolates were screened for sensitivity to the fungicide mefenoxam. All isolates were sensitive, with a mean EC50 value of 0.4 microg/ml mefenoxam, indicating fungicide applications are still a reliable method of black shank management. Results reveal a rapid state-wide shift toward race 1, correlating with the deployment of monogenic resistance and indicate that sexual recombination may be important in generating variation within the pathogen population.
机译：卵菌疫霉（Phytophthora nicotianae）引起的烟草黑胫病是一种重要的烟草疾病。种族1的出现导致主要基因抗性的丧失，并引起了北卡罗来纳州病原体遗传多样性的质疑。种族3在NC中首次报道。第3种种族在具有Phl基因而非Php基因的植物上具有毒性，并在成熟植物上引起严重的病害症状。从部署了Phl基因的位置以及以野生型种族（即种族0）为特征的领域中恢复了种族3的分离株，没有单基因抗性的历史。为了确定第1和第3种族是否可以从第0种族发展为自然变异，并跟踪第1种族和第3种族的Php和Phl毒力损失，对土壤中的一个P. nicotianae进行了侵染，并种植了烟草品种。多基因抗性。五个月后恢复了分离株，并进行了种族筛选。另外，游动孢子分离物衍生自代表三个种族的祖先游动孢子分离物。筛选游动孢子后代以鉴定无性孢子形成过程中毒力的变化。对游动孢子子代的子集进行荧光扩增片段长度多态性分析，以研究通过克隆孢子形成产生的遗传多样性。结果表明，土壤和单孢子分离株的所有种族后代中毒力的增加和/或丧失。第1种是最稳定的表型，在受侵染的土壤中占91％，游动孢子后代中有99.7％保留了毒性表型。五个月后，种族0和3感染的土壤中的种族结构相似。以2：1的比例（种族0：种族3）恢复了种族，而种族1的比例很小。种族0和3的游动孢子后代也分开了。第0种族的子代为67％的种族，而33％的人对Phl基因有毒力（种族3）。同样，来自种族3的后代中有68％保留了父母的强毒表型，有31％失去了强毒表型（种族0），有1％的人对Php基因有毒力（种族1）。每组相关游动孢子内的遗传多样性估计范围为0.17013至0.44196。表型和基因型调查表明，无性孢子形成可能是自然种群变异的主要来源。在北卡罗来纳州的烟草生产地区进行了一次全国性的对烟草假单胞菌种群的调查。从23个县的76个烟草田中获得了分离株，并对其种族和交配类型进行了筛选。在大多数地区，种族1占主导地位，其中59％的田地由90％到100％的种族1构成。田地中种族1的发生与单基因抗性部署的历史呈正相关。种族3在整个州的频率较低，主要是在未部署单基因抗性的野生型种群中。在整个NC中都发现了A1和A2交配类型，并同时从多个字段中进行了恢复。来自田间的分离株配对产生了有活力的卵孢子，这首次表明了烟草假单胞菌有性繁殖的潜力。筛选了一部分调查分离株对杀菌剂甲霜灵的敏感性。所有分离株均敏感，平均EC50值为0.4 microg / ml甲灭沙定，表明杀真菌剂的施用仍然是处理黑胫病的可靠方法。结果显示，全州正在快速向种族1转移，这与单基因抗性的部署相关，并表明性重组可能在病原体种群中产生变异方面很重要。

著录项

  • 作者

    Gallup, Courtney Anne.;

  • 作者单位

    North Carolina State University.;

  • 授予单位 North Carolina State University.;
  • 学科 Agriculture Plant Pathology.Health Sciences Public Health.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 214 p.
  • 总页数 214
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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