纳他霉素对芒果采后胶孢炭疽菌的抑菌效果及机理

以纳他霉素为抑菌剂, 实验测定了离体条件下不同浓度纳他霉素对胶孢炭疽菌(Colletotrichum gloeosporioides)的孢子萌发及菌丝生长的抑制效果, 以及活体损伤接种炭疽病菌后, 纳他霉素对芒果(Mangifera indica)果实炭疽病的防治效果。通过测定纳他霉素处理后胶孢炭疽菌的细胞膜相对渗透率、可溶性蛋白含量、细胞膜完整性、孢子内活性氧水平和线粒体分布情况, 初步探明其抑菌机理。结果表明, 3 mg?L ^-1纳他霉素可显著抑制胶孢炭疽菌孢子萌发、芽管伸长和菌落生长, 80 mg?L ^-1纳他霉素可有效抑制芒果贮存过程中果实炭疽病斑的扩展。纳他霉素处理后胶孢炭疽菌细胞膜相对渗透率和可溶性蛋白含量增加; 2 mg?L ^-1纳他霉素处理8小时, 处理组胶孢炭疽菌孢子细胞膜损伤染色率为33.6%, 对照组染色率为13.9%; 处理组胞内活性氧产生染色率达46.9%, 比对照组高39.7%; 同时观察到纳他霉素使胞内线粒体分布不均且荧光信号微弱。以上结果表明, 纳他霉素可以破坏胶孢炭疽病菌细胞膜, 诱导活性氧大量积累, 并降低线粒体活性, 从而干扰菌体正常生理活性, 使其代谢活动受影响, 从而达到抑菌目的。

Antifungal Activity and Mechanisms of Natamycin Against Colletotrichum gloeosporioides in Postharvest Mango Fruit

In this study, we examined the inhibitory effects of natamycin at different concentrations on the conidial germination and mycelial growth of Colletotrichum gloeosporioides in vitro as well as the controlled effect of natamycin on postharvest anthracnose of mango (Mangifera indica) fruit inoculated with C. gloeosporioides. To further explore the underlying antifungal mechanism, we analyzed the membrane permeability, soluble protein content, changes in cell membrane integrity, intracellular reactive oxygen species (ROS) level and mitochondrial distribution in C. gloeosporioides after natamycin treatment. Natamycin at 3 mg?L ^-1 effectively suppressed the conidial germination, germ tube elongation and mycelial growth of C. gloeosporioides. Also, 80 mg?L ^-1natamycin significantly inhibited the expansion of anthracnose lesions in mango fruit during storage. Furthermore, natamycin treatment increased the relative permeability and soluble protein content in the cell membrane of C. gloeosporioides. After 8h treatment with natamycin 2 mg?L ^-1, the staining rate of damaged cell membranes in C. gloeosporioides was 33.6% and 13.9% in the control. The staining rate of intracellular ROS reached 46.9% in treated conidia, which was 39.7% higher than that of the control. Natamycin treatment caused heterogeneous distribution of intracellular mitochondria along with weaker fluorescence as compared with the control. In summary, natamycin can destroy the cell membrane of C. gloeosporioides, induce ROS accumulation and reduce mitochondrial activity, thus interfering in the normal physiological activity of C. gloeosporioides and affecting its metabolic activities.