1State Key Laboratory of Crop Stress Biology in Arid Areas and College of Plant Protection, Northwest A&F University, Yangling, Shaanxi Province, China.
2Department of Plant Pathology and Microbiology, Iowa State University, Ames, IA, U.S.A.
Plant Dis. 2019 Aug;103(8):1889-1901. doi: 10.1094/PDIS-10-18-1794-RE. Epub 2019 Jun 3.
Apple fruit spot disease has caused serious economic losses for years in China since the widespread application of fruit bagging in production. Although the three genera , , and have been reported to be the causal agents, studies on the disease etiology and pathogen biology are still sparse. Here, we report characterization of eight fungal isolates from lesions on 126 symptomatic fruit samples collected in Shaanxi Province, China. Pathogenicity of the isolates was assessed. DNA sequences were obtained at four loci, including D1/D2 domains of the large-subunit nrRNA gene, internal transcribed spacer regions 1 and 2, 5.8S nrDAN gene, a fragment of the actin gene, and a fragment of the β-tubulin. Based on phylogenetic analysis and morphological features, three new species were found: , , and . In addition, we made the first report of as a plant pathogen. Temperature and moisture significantly affected in vitro conidial germination of five -like species, and their impact on infection of apple fruit was tested using . Conidia of five species germinated from 15 to 35°C in free water; four of the species had optimum temperature around 25°C, whereas conidia of had an optimum temperature of 30°C. Conidial germination rate increased as relative humidity (RH) increased. The five isolates had relatively high conidial germination rates at RH > 97%, with a significant decline at 95% RH. Incidence of infection also increased in proportion to RH. In free water, conidial germination was relatively unaffected by temperature.
苹果果实斑点病自中国生产中广泛应用果实套袋以来，多年来已造成严重的经济损失。虽然已报道有三个属 、 和 是该病的病原体，但对该病病因和病原体生物学的研究仍然很少。在这里，我们报道了从中国陕西省 126 个有症状的果实样本的病变中分离得到的 8 个真菌分离物的特征。评估了分离物的致病性。从四个基因座获得了 DNA 序列，包括大亚基 nrRNA 基因的 D1/D2 结构域、内部转录间隔区 1 和 2、5.8S nrDAN 基因、肌动蛋白基因的片段和β-微管蛋白的片段。基于系统发育分析和形态特征，发现了三个新种： 、 和 。此外，我们首次报道 是一种植物病原体。温度和湿度显著影响了 5 种类似种的体外分生孢子萌发，并用 测试了它们对苹果果实感染的影响。五种物种的分生孢子在 15 到 35°C 的自由水中萌发；其中四种在 25°C 左右的温度下具有最佳温度，而 的分生孢子最佳温度为 30°C。随着相对湿度（RH）的增加，分生孢子的萌发率增加。五种分离物在 RH>97%时具有相对较高的分生孢子萌发率，在 95% RH 时显著下降。感染的发生率也随 RH 的增加而增加。在自由水中，温度对分生孢子的萌发影响相对较小。
