Hurtado-Gonzales O P, Aragon-Caballero L M, Flores-Torres J G, Man in 't Veld Willem, Lamour K H
Entomology and Plant Pathology Department, University of Tennessee, Knoxville, Tennessee 37996, USA.
Mycologia. 2009 Jul-Aug;101(4):496-502. doi: 10.3852/08-079.
Natural Phytophthora hybrids (P. nicotianae x P. cactorum) infecting loquat in Peru and Taiwan were characterized with AFLP (amplified fragment length polymorphism) markers, the internal transcribed spacer (ITS) region and the phenol acid carboxylase gene (Pheca) and inheritance of the mitochondrial cytochrome oxidase I gene (coxI). AFLP profiles of two Taiwanese isolates recovered in 1995 were polymorphic in approximately 50% of the fragments whereas five Peruvian isolates, recovered 2002-2003 and 2007, showed no genotypic variation. Sequencing analysis of the cloned ITS region resulted in the identification of sequences with high homology to either P. nicotianae (99%) or P. cactorum (97%). Direct sequence analysis of the Pheca gene revealed 13 heterozygous sites suggesting the presence of both P. nicotianae and P. cactorum genes in P. hybrids isolates. Melting analyses of coxI suggested that all seven Phytophthora hybrids inherited the mitochondrial DNA from P. nicotianae. Our results suggest that Phytophthora hybrids from Peru might have originated from a single hybridization event and that the two isolates from Taiwan might have originated through different hybridization events. The Peruvian hybrids appear to have persisted at least 3 y at three locations. Possible factors influencing the population structure of Phytophthora hybrids infecting loquat are discussed.
利用扩增片段长度多态性（AFLP）标记、内转录间隔区（ITS）区域、酚酸羧化酶基因（Pheca）以及线粒体细胞色素氧化酶I基因（coxI）的遗传特性，对在秘鲁和台湾感染枇杷的天然疫霉属杂种（烟草疫霉x恶疫霉）进行了特征分析。1995年分离得到的两个台湾分离株的AFLP图谱中，约50%的片段具有多态性，而2002 - 2003年和2007年分离得到的五个秘鲁分离株未表现出基因型变异。对克隆的ITS区域进行测序分析，结果鉴定出与烟草疫霉（99%）或恶疫霉（97%）具有高度同源性的序列。对Pheca基因的直接序列分析揭示了13个杂合位点，表明杂种疫霉分离株中同时存在烟草疫霉和恶疫霉的基因。coxI的熔解分析表明，所有七个疫霉属杂种均从烟草疫霉继承了线粒体DNA。我们的结果表明，来自秘鲁的疫霉属杂种可能起源于单一杂交事件，而来自台湾的两个分离株可能起源于不同的杂交事件。秘鲁的杂种似乎在三个地点至少持续存在了3年。文中讨论了影响感染枇杷的疫霉属杂种群体结构的可能因素。
