Wang Nan-Yi, Zhang Ke, Huguet-Tapia Jose C, Rollins Jeffrey A, Dewdney Megan M
All authors: Department of Plant Pathology, University of Florida, Gainesville, and first, second, and fifth authors: Citrus Research and Education Center, University of Florida, Lake Alfred.
Phytopathology. 2016 Nov;106(11):1300-1310. doi: 10.1094/PHYTO-12-15-0316-R. Epub 2016 Jul 26.
Phyllosticta citricarpa, the citrus black spot pathogen, was first identified in Florida in March 2010. Subsequently, this pathogen has become established in Florida but can be easily confused with the endemic nonpathogenic citrus endophyte P. capitalensis. In this study, the mating-type (MAT) loci of P. citricarpa and P. capitalensis were identified via draft genome sequencing and were characterized at the structural and sequence levels. P. citricarpa was determined to have an idiomorphic, heterothallic MAT locus structure, whereas P. capitalensis was found to have a single MAT locus consistent with a homothallic mating system. A survey of P. citricarpa isolates from Florida revealed that only the MAT1-2 idiomorph existed in the Floridian population. In contrast, isolates collected from Australia exhibited a 1:1 ratio of MAT1-1 and MAT1-2 isolates. Development and analysis of simple sequence repeat markers revealed a single multilocus genotype (MLG) in the Floridian population (n = 70) and 11 MLG within the Australian population (n = 24). These results indicate that isolates of P. citricarpa from Florida are likely descendent from a single clonal lineage and are reproducing asexually. The disease management focus in Florida will need to be concentrated on the production and dispersal of pycnidiospores.
柑橘黑点病菌（Phyllosticta citricarpa）于2010年3月在佛罗里达州首次被发现。随后，这种病原菌在佛罗里达州定殖，但很容易与当地的非致病性柑橘内生菌首都叶点霉（P. capitalensis）混淆。在本研究中，通过基因组草图测序鉴定了柑橘黑点病菌和首都叶点霉的交配型（MAT）位点，并在结构和序列水平上对其进行了表征。确定柑橘黑点病菌具有异形、异宗配合的MAT位点结构，而首都叶点霉具有与同宗配合交配系统一致的单一MAT位点。对来自佛罗里达州的柑橘黑点病菌分离株的调查显示，在佛罗里达种群中仅存在MAT1-2等位形。相比之下，从澳大利亚收集的分离株中MAT1-1和MAT1-2分离株的比例为1:1。简单序列重复标记的开发和分析显示，佛罗里达种群（n = 70）中有一个多位点基因型（MLG），而澳大利亚种群（n = 24）中有11个MLG。这些结果表明，来自佛罗里达州的柑橘黑点病菌分离株可能来自单一的克隆谱系，并且正在进行无性繁殖。佛罗里达州的病害管理重点将需要集中在分生孢子器孢子的产生和传播上。
