甜瓜链格孢菌的鉴定及其CAZymes活性研究

Identification of Alternaria alternata from Melon and Study of Its Carbohydrate Active Enzymes Activity

对从贮藏期间患黑斑病的甜瓜中分离出的3株真菌A2015、A2018、A2019进行形态学鉴定,结果表明,这3株菌株均属链格孢属(Alternaria Nees),生长初期呈白色,菌丝横纵交错,呈絮状,后期分生孢子呈暗色倒棒状,具有横纵隔膜。对分离所得菌株及购自中国微生物菌种保藏管理委员会普通微生物中心(CGMCC)的梨黑斑链格孢(Alternaria gaisen)菌株3.18017进行多聚半乳糖醛酸酶(PG)、果胶甲酯酶(PME)、纤维素酶(Cx)、β-葡萄糖苷酶(β-Glu)活性测定,研究链格孢侵染甜瓜时所产生的具有侵染力的酶活特性。结果表明:在4株链格孢侵染甜瓜过程中,PG活性在第3天时达到最高,其中菌株A2015的酶活最高达到20924.25μg·h^(-1)·g^(-1) FW;Cx和β-Glu活性第6天时达到最高,分别高达250.20、8619.21μg·h^(-1)·g^(-1) FW;PME活性第7天时达到最高,为0.24μg·h^(-1)·g^(-1) FW。说明链格孢在侵染甜瓜时产酶顺序依次为PG、Cx、β-Glu、PME,由此顺序逐步对细胞壁进行降解、侵染进入瓜体内部。此研究结果可以有效为后期针对性防治甜瓜黑斑病以及甜瓜抵御链格孢的入侵提供病原菌自身特性的理论基础。

Morphological identification of three strains of fungi A2015, A2018 and A2019 isolated from muskmelon with black spot disease during storage were carried out. The results showed that all the three strains belonged to Alternaria Nees. At the initial stage of growth, they were white, the hyphae were crisscrossing and flocculent, and the conidia were dark inverted rod-shaped and had transverse and longitudinal septa in later stage. The activity of polygalacturonase (PG), pectin methylesterase (PME), cellulase (Cx) and β-Glucosidase(β-Glu) of the isolated three muskmelon Alternaria alternata and the Alternaria gaisen strain 3.18017 purchased from China General Microbiological Culture Collection Center (CGMCC) were determined to study the activity characteristics of enzymes with infectivity produced from Alternaria infecting muskmelon. The results showed that during the infection of melons by four Alternaria alternata strains, PG activity reached the highest at the third day, and the enzyme activity of strain A2015 reached 20 924.25 μg·h^(-1)·g^(-1) FW;Cx and β-Glu activity reached the highest at the 6th day, up to 250.20 μg·h^(-1)·g^(-1) FW and 8 619.21 μg·h^(-1)·g^(-1) FW respectively;PME activity reached the highest at the 7th day, which was 0.24 μg·h^(-1)·g^(-1) FW. Which suggested that the order of enzyme production was PG, Cx, β-Glu and PME in Alternaria alternata infection of melon, in this order, the cell wall was gradually degraded and infected, the fungi invaded into the melon body. The results could effectively provide a theoretical basis of the characteristics of the pathogens for the later targeted prevention and treatment of melon black spot disease and defence against the invasion of Alternaria alternata.