广东省番石榴褐斑病的病原分离及鉴定

番石榴(Psidium guajava Linn.)起源于墨西哥,是热带和南亚热带地区普遍种植的水果[1].番石榴也是我国华南地区畅销的水果之一,2018年广东省的番石榴种植面积达1.25万hm2.2018年7月,在广州水果世界岭南鲜果基地调查发现,部分番石榴枝条出现不连续的褐色斑块,叶片和花器的花瓣呈现从边缘向中间扩...

Pathogen isolation and identification of brown spot disease of Psidium guajava Linn. in Guangdong

In order to clarify the pathogen causing brown spot of Psidium guajava Linn., and provide a theore-tical basis for effective prevention and treatment of the disease, the pathogen of the brown spot of Psidium guajava Linn. was isolated and identified by molecular and morphological methods. The pathogen was obtained by tissue separation method, and the pathogenicity of the pathogen was determined by Koch′s rule. The morphological characteristics of the conidia of the pathogen were observed by optical microscope, and the sequence of the rDNA-ITS and RPB2 of the pathogen was analyzed by online Blast. The BLAST online alignment showed that the ITS sequence of the pathogen was 100% homologous with multiple strains of Alternaria alternata and Alternaria tenuissima, the homology of the RPB2 sequence of the pathogen with the strains of A. alternata and A. tenuissima reached 99.86%. According to the latest references, A. tenuissima (Fr.) Wiltshire was not an independent species but was a synonym of A. alternata (Fr.) Keissler. Combined with the pathological characteristics of pathogenic fungi, pathogenicity determination and phylogenetic tree analysis, the pathogen of guava brown spot disease in Guangdong was identified as A. alternata.