苹果轮纹病菌侵染机制的研究(英文)

苹果轮纹病菌(Botryosphaeriaberengrianaf.sppiricola)能在培养基及活体内产生一系列果胶酶:多聚半乳糖醛酸酶(PG)、聚甲基半乳糖醛酸酶(PMG)、多聚半乳糖醛酸反式消除酶(PGTE)和果胶甲基反式消除酶(PMTE)。其中PG和PMG是降解果实胞壁的主要酶类,在整个致病过程中起重要作用。从结果可看出PG活性随着侵染的进展而升高,PMG的作用在侵染前期更大一些,2种果胶酶可能是引起被接种苹果果皮上还原糖变化的重要因素。接种与未接种果实果皮的pH值差异随侵染进程而降低,接种40d后,接种处pH值开始低于健康组织的pH值,这一变化可能造成细胞壁软化而有利于PG和PMG活动。接种后10～20d,PG活性及组织中还原糖的增长速度比其他阶段要快。对侵染点的病原组织学研究进一步表明,病菌产生的各种果胶酶不论是在侵染初期还是后期都是重要的致病物质。

Study on the infection mechanism of apple ring rot disease

Apple ring rot pathogen (Botryosphaeria berengriana f. sp piricola) can produce a series of pectinases in vitro and in vivo, including polygalacturonase(PG), polymethylgalacturonase (PMG), polygalacturonic acid transeliminase (PGTE) and pectin methyltranseliminase(PMTE). Among them, PG and PMG are major enzymes to degrade fruit cell wall and play an important role in pathogenesis. Results suggested that PG activity increased constantly during pathogen infection, while PMG was more active at the early infection period. Both pectinases might be involved in relevant change in reducing sugars in the inoculated fruit skin. The difference in pH between inoculated and non-inoculated fruit skin gradually became smaller in the process of pathogen infection, and at 40 d after inoculation the pH in inoculated tissue became lower than in healthy tissues. The pH change might facilitate PG and PMG actions and hasten cell wall softened. From 10 to 20 d after inoculation, PG activity and reducing sugar released from tissue increased more quickly than other stages. The histological study of pathogen showed that pectinases produced from pathogen served as important pathogenetic agents throughout infection process.