First, second, and third authors, Tasmanian Institute of Agriculture, University of Tasmania, Burnie, Tasmania 7320, Australia; fourth and fifth authors, Plant Pathology & Plant-Microbe Biology Section, School of Integrative Plant Science, Cornell AgriTech at the New York State Agricultural Experiment Station, Cornell University, Geneva, NY 14456.
Phytopathology. 2019 Jan;109(1):155-168. doi: 10.1094/PHYTO-08-17-0280-R. Epub 2018 Nov 13.
Tan spot, caused by Didymella tanaceti, is one of the most important foliar diseases affecting pyrethrum in Tasmania, Australia. Population dynamics, including mating-type ratios and genetic diversity of D. tanaceti, was characterized within four geographically separated fields in both late winter and spring 2012. A set of 10 microsatellite markers was developed and used to genotype 774 D. tanaceti isolates. Isolates were genotypically diverse, with 123 multilocus genotypes (MLG) identified across the four fields. Fifty-eight MLG contained single isolates and P analysis estimated that, within many of the recurrent MLG, there were multiple clonal lineages derived from recombination. Isolates of both mating types were at a 1:1 ratio following clone correction in each field at each sampling period, which was suggestive of sexual recombination. No evidence of genetic divergence of isolates of each mating type was identified, indicating admixture within the population. Linkage equilibrium in two of the four field populations sampled in late winter could not be discounted following clone correction. Evaluation of temporal changes in gene and genotypic diversity identified that they were both similar for the two sampling periods despite an increased D. tanaceti isolation frequency in spring. Genetic differentiation was similar in populations sampled between the two sampling periods within fields or between fields. These results indicated that sexual reproduction may have contributed to tan spot epidemics within Australian pyrethrum fields and has contributed to a genetically diverse D. tanaceti population.
块斑病，由 Tanacetum 角斑病菌引起，是影响澳大利亚塔斯马尼亚除虫菊的最重要叶部病害之一。在 2012 年末至春季，对四个地理位置分离的田间的 Tanacetum 角斑病菌种群动态（包括交配型比例和遗传多样性）进行了研究。开发了一套 10 个微卫星标记，并用于对 774 个 Tanacetum 角斑病菌分离株进行基因分型。分离株的基因型多样化，在四个田间共鉴定出 123 个多位点基因型（MLG）。58 个 MLG 包含单个分离株，P 分析估计，在许多反复出现的 MLG 中，存在多个源自重组的无性系。在每个田间的每个采样期，经克隆校正后，两种交配型的分离株比例均为 1:1，表明存在有性重组。没有发现每种交配型的分离株存在遗传分化的证据，表明种群内存在混合。在冬季末采样的四个田间种群中的两个种群，经克隆校正后，不能排除连锁平衡。对基因和基因型多样性的时间变化的评估表明，尽管春季 Tanacetum 角斑病菌的分离频率增加，但两个采样期的基因和基因型多样性相似。田间内或田间间两个采样期的种群遗传分化相似。这些结果表明，有性繁殖可能导致了澳大利亚除虫菊田块斑病的流行，并导致了 Tanacetum 角斑病菌遗传多样性的增加。
