Chen Daniel, Fӧrster Helga, Adaskaveg James E
Department of Microbiology and Plant Pathology, University of California, Riverside, CA 92521.
Plant Dis. 2021 Aug;105(8):2114-2121. doi: 10.1094/PDIS-07-20-1421-RE. Epub 2021 Sep 7.
Natamycin is a biofungicide that was registered in the United States in 2016 and approved in California in 2017 for postharvest use on citrus and stone fruits. It has been used as a food preservative for many decades, with no resistance ever observed to date. The objective of this study was to determine baseline sensitivities for mycelial growth of 43 to 72 isolates of seven postharvest pathogens to natamycin and the resistance potential of . Mean effective concentrations to inhibit mycelial growth by 50% (EC values), as determined by the spiral gradient method, were 0.90 μg/ml for , 0.76 μg/ml for , 3.20 μg/ml for , 0.17 μg/ml for , 1.54 μg/ml for , 1.14 μg/ml for , and 0.48 μg/ml for . Distributions of EC values for each pathogen were unimodal and mostly normal with no outliers detected. Natamycin was also inhibitory to spore germination with values for five of the species similar to those for mycelial growth. Microscopically, natamycin generally arrested spores at the pregermination swelling stage. Mass platings of a conidial mixture of 10 isolates of were inoculated on agar media with 2.5-log radial concentration gradients of natamycin or fludioxonil, and a conidial mixture of 10 isolates of were plated on media amended with natamycin or propiconazole. No resistant isolates were observed for both species to natamycin or for to propiconazole, whereas a resistance frequency of 4.5 × 10 to 3.1 × 10 was calculated for to fludioxonil. The wide spectrum of activity against different fungal pathogens and a low resistance potential support the registration of natamycin as a postharvest treatment and its integration into an integrated pest management program with other practices including sanitation and rotation of other fungicides with different modes of action.
纳他霉素是一种生物杀菌剂，于2016年在美国注册，并于2017年在加利福尼亚州获批用于柑橘和核果的采后处理。它作为食品防腐剂已使用了数十年，至今未观察到耐药性。本研究的目的是确定7种采后病原菌的43至72个分离株对纳他霉素的菌丝生长基线敏感性以及……的耐药潜力。通过螺旋梯度法测定，抑制菌丝生长50%的平均有效浓度（EC值），对……为0.90μg/ml，对……为0.76μg/ml，对……为3.20μg/ml，对……为0.17μg/ml，对……为1.54μg/ml，对……为1.14μg/ml，对……为0.48μg/ml。每种病原菌的EC值分布呈单峰且大多呈正态分布，未检测到异常值。纳他霉素对孢子萌发也有抑制作用，其中5个物种的孢子萌发抑制值与菌丝生长抑制值相似。在显微镜下，纳他霉素通常使孢子在萌发前的肿胀阶段停滞。将10个……分离株的分生孢子混合物大量接种在含有纳他霉素或咯菌腈2.5对数径向浓度梯度的琼脂培养基上，将10个……分离株的分生孢子混合物接种在添加了纳他霉素或丙环唑的培养基上。两种物种对纳他霉素均未观察到耐药分离株，对……对丙环唑也未观察到耐药分离株，而对……对咯菌腈的耐药频率计算为4.5×10至3.1×10。纳他霉素对不同真菌病原菌的广泛活性和低耐药潜力支持将其注册为采后处理剂，并将其纳入综合虫害管理计划，与包括卫生措施和轮换使用其他不同作用方式的杀菌剂等其他措施相结合。
