苹果梨黑斑病的发生及侵染过程

Occurrence and infection of Alternaria rot of Pingguoli pear, Pyrus pyrifolia

苹果梨果实的黑斑病为典型的潜伏侵染性病害,采后冷藏60天,表面光滑无任何症状,采后90天开始,皮孔或萼筒伸出黑灰色菌丝,进而其周围组织坏死形成黑斑。采后100天,黑斑病的发病率达28.86%。黑斑病是由链格孢Alternaria alternata(Fr.) Keissl.侵染引起的,链格孢在采前可经两条途径侵入苹果梨果实。一是在花朵开放时经花柱侵入,花后50天定殖于花柱的病原菌通过萼室间组织陆续进入心室,至采收时,心室中链格孢出现率可达45%;二是自果实膨大期开始侵入果皮,潜伏于皮下组织,至采收时萼端、胴部、梗端链格孢的带菌率分别为40%、24%和42.8%。

Alternaria rot of Pingguoli pear was a disease with latent infection character. Fruit surface showed sound within 60 days storage at cool condition （0℃, RH 85%- 90% ）, black-gray hyphae could be seen in lenticels or calyx tube after 90 days storage, then tissues around lenticels collapsed and resulted in visible black spot. The incidence of Alternaria rot reached 28.86% at 100 days storage. The causal fungus isolated from the black spots was identified as Alternaria alternata （Fr.）Keissl. This pathogen was able to infect fruits through two pathways during pear growing season. The pathogenic fungus can colonize firstly on styles at blossoming stage and grow into carpel cavities gradually after 50 days of petal fall. The colonization of the pathogen could be 45% in carpel cavity till harvest time. It can also attack fruit surface and remained latent under epidermal cells during fruit development. The colonization of the pathogen at calyx end, middle part and stem end of fruit peel was 40%, 24% and 42.8% respectively at harvest time.