Department of Plant Pathology and Environmental Microbiology, Fruit Research and Extension Center, The Pennsylvania State University, Biglerville, PA 17307.
Plant Dis. 2023 Aug;107(8):2474-2482. doi: 10.1094/PDIS-08-22-1966-RE. Epub 2023 Aug 19.
Bitter rot is a major disease of apple fruit in warm and humid regions. It is caused by various species in the and species complexes, of which of the species complex is most common in the Mid-Atlantic region of the United States. While bitter rot management begins with good cultural practices, fungicides are generally used for consistent control. Fungicides should be applied before or during infection periods, but the timing of infection is unclear due to the hemibiotrophic lifestyle of the causal species. To determine when infection periods occur, we quantified spore dispersal throughout three growing seasons and compared the temporal susceptibility of apples in two seasons of field trials. Spores were detected in rainwater from bud break to leaf drop, with the highest spore quantities in the summer and early fall correlating with optimal temperatures for . Late-season-inoculated fruit had more bitter rot than early-season-inoculated fruit, but this was also positively correlated with periods of optimal temperatures and moisture for infection. In the context of previous experiments, these results suggest that infection periods are primarily determined by temperature and moisture rather than apple fruit phenology. Based on the relative numbers of spores and biotrophic and necrotrophic infections, only a tiny proportion of spores establish viable biotrophic infections, but a relatively high proportion of biotrophic infections switch to necrotrophy. We suggest bitter rot management should focus on preventing initial biotrophic infections by protecting apples during weather conditions that favor infection.
酸腐病是温暖潮湿地区苹果果实的主要病害。它是由 和 种复合体中的各种物种引起的，其中 种复合体在美国中大西洋地区最为常见。虽然酸腐病的管理始于良好的栽培措施，但通常使用杀菌剂进行持续控制。杀菌剂应在感染期之前或期间施用，但由于致病物种的半生物营养生活方式，感染期的时间尚不清楚。为了确定感染期的发生时间，我们在三个生长季节内量化了孢子的扩散，并在两个田间试验季节比较了苹果的时间易感性。在萌芽到落叶期间，从雨水检测到孢子，夏季和初秋的孢子数量最高，与 的最佳温度相关。与早期接种的果实相比，晚期接种的果实的酸腐病更为严重，但这也与感染的最佳温度和湿度期呈正相关。根据先前实验的结果，这些结果表明感染期主要由温度和湿度决定，而不是苹果果实的物候。基于孢子的相对数量以及生物营养和坏死感染，只有一小部分孢子建立了可行的生物营养感染，但相对较高比例的生物营养感染转变为坏死。我们建议酸腐病的管理应侧重于通过在有利于感染的天气条件下保护苹果来预防初始的生物营养感染。
