Section of Plant Pathology and Plant-Microbe Biology, School of Integrative Plant Science, Cornell University, Ithaca, NY 14853.
Section of Plant Pathology and Plant-Microbe Biology, New York State Agricultural Experiment Station, Cornell University, Geneva NY 14456.
Plant Dis. 2019 Jan;103(1):125-131. doi: 10.1094/PDIS-04-18-0695-RE. Epub 2018 Nov 16.
Paecilomyces rot of apples is a postharvest disease caused by the thermotolerant fungus Paecilomyces niveus (Byssochlamys nivea). The etiology of disease and the activity of fungicides against P. niveus are not yet well understood. This study evaluated the ability of P. niveus to infect 'Gala' apples growing in a conventionally managed orchard. In addition, the sensitivity of P. niveus isolates to postharvest fungicides difenoconazole, fludioxonil, and pyrimethanil was characterized for isolates from both agricultural and nonagricultural environments. Apples were wounded and mock-inoculated or inoculated with P. niveus in early July. At the time of harvest, 8 weeks after wounding, the inoculated apples had significantly larger lesions than mock-inoculated apples (P < 0.005). The average diameter of lesions on wound-inoculated apples was 11.17 mm ± 6.82 SD, while the average diameter of mock-inoculated lesions was 3.34 mm ± 1.85 SD. Disease symptoms in the orchard were similar to postharvest symptoms of Paecilomyces rot. Symptoms included a brown, flattened, circular lesion with faint concentric rings. The necrosis of mesocarp was firm and roughly U-shaped. Baseline isolates of P. niveus, from nonagricultural environments, were used to determine the effective fungicide dose at which growth was inhibited by 50% (EC). Furthermore, fungicide sensitivity of P. niveus isolates was examined using relative growth assays at the mean baseline EC values to compare baseline isolates with isolates obtained from commercial apple orchards where they were likely exposed to fungicides. Among the exposed isolates, reduced sensitivity to all fungicides was observed, but significant differences between baseline and exposed isolates were only observed with fludioxonil (P < 0.0001). This is the first report demonstrating that P. niveus can infect apples that are wound-inoculated in the orchard and that isolates from agricultural environments are less sensitive to common fungicides, especially fludioxonil. This finding may have implications for the control of this postharvest diseases. Whether natural infections of apples by P. niveus is initiated in the orchard or during postharvest has yet to be determined.
苹果皮落孢霉病是一种由耐热真菌层出镰刀菌（Byssochlamys nivea）引起的采后病害。该病害的病因和杀菌剂对层出镰刀菌的活性尚不清楚。本研究评估了层出镰刀菌感染常规管理果园中“嘎拉”苹果的能力。此外，还对来自农业和非农业环境的层出镰刀菌分离物对采后杀菌剂苯醚甲环唑、氟啶胺和嘧菌腙的敏感性进行了表征。7 月初，苹果受了伤并进行了模拟接种或接种了层出镰刀菌。在收获时，即受伤后 8 周，接种苹果的病斑明显大于模拟接种苹果（P < 0.005）。接种苹果的病斑平均直径为 11.17 毫米±6.82 标准差，而模拟接种病斑的平均直径为 3.34 毫米±1.85 标准差。果园中的病症与采后皮落孢霉病的症状相似。症状包括棕色、扁平、圆形病斑，有微弱的同心环。中果皮坏死组织坚硬，大致呈 U 形。从非农业环境中分离出的基础层出镰刀菌被用于确定 50%生长抑制的有效杀菌剂剂量（EC）。此外，还使用相对生长测定法，在平均基线 EC 值下，检查了层出镰刀菌分离物对杀菌剂的敏感性，以比较基线分离物与从可能接触过杀菌剂的商业苹果园获得的分离物。在暴露的分离物中，观察到对所有杀菌剂的敏感性降低，但仅在与暴露分离物相比时，对氟啶胺的敏感性差异显著（P < 0.0001）。这是第一个证明层出镰刀菌可以感染果园中受伤接种的苹果的报告，并且来自农业环境的分离物对常用杀菌剂，尤其是氟啶胺的敏感性降低。这一发现可能对这种采后病害的控制有影响。目前尚不清楚苹果是否是在果园中或采后被层出镰刀菌自然感染的。
