红肉蜜柚内生菌的分离及抑菌活性分析

Isolation,identification and antimicrobial activity of endophytes from red-fleshed sweet pomelo

选取牛肉膏蛋白胨、马铃薯葡萄糖琼脂(PDA)和高氏1号3种培养基,利用组织块法对红肉蜜柚(Citrus grandis)果实的内生菌进行分离纯化,得到9株菌株,经生物学性状分析,9株菌株均为放线菌,分属于诺卡氏菌属(Norcardia)和链霉菌属(Streptomyces)。采用平皿对峙法测定供试菌株的拮抗活性,有6株表现出不同程度的拮抗作用,占全部分离菌株的66.7%,其中1株对大肠杆菌(Escherichia coli)、4株对金色葡萄球菌(Staphylococcus aureus)、3株对枯草芽孢杆菌(Bacillus subtilis)具有明显的抑菌效果;在3种柑橘病原菌的抑菌试验中,有7株菌株表现出不同程度的拮抗作用,占全部分离菌株的77.8%,其中7株对指状青霉(Penicillium digitatum Sacc.)、3株对意大利青霉(Penicillium italicum Wehmer)、3株对柑橘链格孢(Alternaria citri Ellis et.Pierce)的抑菌率超过75%。菌株P1、R2对3种柑橘病原菌均有很高的抑菌活性。

Nine endophytic strains were isolated from mature fruit of red-flesh sweet pomelo （ Citrus grandis ） by tissue explant isolation method on 3 sorts of culture mediums, including beef extract peptone medium, PDA media and Gause＇s No. 1 medium. By morphologic and microscopical characteristics, the 9 strains were identified as endophytic actinomycetes, and were classified into 2 genera of Norcardia （ 4 strains ） and Streptomyces （ 5 strains ） . Antimicrobial activities of these actinomycetes were determined by confronting cultivation on PDA plate method. The results showed that 6 strains performed different degrees of antagonistic activity against Escherichia coli （ 1 strain ）, Staphylococcus aureus （ 4 strains ） and Bacillus subtilis （ 3 strains ） , accounting for 66.7% of all strains. And 7 strains possessed significantly higher antifungal activity against Penicillium digitatum Sacc. （ 7 strain ） , P. italicum Wehmer （ 3 strains ） and Alternaria cirri Ellis et. Pierce （ 3 strains ）, accounting for 77.8% of all strains, with more than 75% inhibition rate. The strains of P1 and R2 exhibited stronger antagonistic activity against the 3 kinds of citrus pathogens.