Department of Plant Pathology, China Agricultural University, Haidian District, Beijing 100193, China.
Institute of Plant and Environment Protection, Beijing Academy of Agriculture and Forestry Sciences, Haidian District, Beijing 100097, China.
Plant Dis. 2021 Jan;105(1):60-70. doi: 10.1094/PDIS-01-20-0130-RE. Epub 2020 Nov 10.
Watermelon is an economically important crop in China and is commonly affected by -like leaf blight that can result in significant economic losses. In this study, 830 isolates, recovered from symptomatic watermelon leaves, were identified based on morphological traits, pathogenicity, and multilocus sequence analyses of glyceraldehyde-3-phosphate dehydrogenase (), histone 3 (), the internal transcribed spacer of ribosomal DNA (rDNA ITS), and the RNA polymerase II second largest subunit (). Watermelon isolates grouped to five species and one unclassified species. They were , , , , , and sp. Notably, was the most prevalent (73.5%) of the six isolated species, followed by (25.0%), (1.1%), sp. (0.2%), (0.1%), and (0.1%). Pathogenicity tests demonstrated that all six species could produce brown necrotic lesions on detached leaves of watermelon. The average disease incidence (75.1%) and average disease index (60.8) of watermelon resulting from inoculation of leaves with were significantly higher than levels resulting from (52.9% and 37.2) and (47.5% and 30.8). Inoculation with sp. resulted in a disease incidence (70.0%) and disease index (51.5), which were lower than those of . The disease incidence and disease index in watermelon leaves inoculated with the one isolate of and the one isolate of present in the inoculated leaves were 28.9% and 16.4, and 48.9% and 31.4, respectively. Results of the study indicate that species associated with watermelon leaf blight in China are more diverse than that has been previously reported. This is the first report globally of , , and an unclassified species as causal agents of leaf blight on watermelon.
西瓜在中国是一种重要的经济作物，常受到类似西瓜疫病的影响，导致重大经济损失。本研究从病叶中分离到 830 个菌株，根据形态特征、致病性和甘油醛-3-磷酸脱氢酶（）、组蛋白 3（）、核糖体 DNA（rDNA ITS）内部转录间隔区和 RNA 聚合酶 II 第二大亚基（）的多位点序列分析对其进行了鉴定。西瓜分离物分为 5 个种和 1 个未分类种。它们是、、、、和 sp. 值得注意的是，在这 6 个分离种中，最普遍的是（73.5%），其次是（25.0%）、（1.1%）、sp.（0.2%）、（0.1%）和（0.1%）。致病性试验表明，所有 6 个种都能在西瓜离体叶片上产生棕色坏死斑。叶片接种引起的西瓜平均发病率（75.1%）和平均病情指数（60.8）明显高于叶片接种引起的发病率（52.9%）和病情指数（37.2%）和（47.5%）和病情指数（30.8%）。接种 sp.引起的发病率（70.0%）和病情指数（51.5%）低于。接种叶片中一个 种和一个 的分离物引起的发病率和病情指数分别为 28.9%和 16.4%，以及 48.9%和 31.4%。研究结果表明，与中国西瓜叶疫病相关的种比以前报道的更为多样化。这是首次在全球范围内报道、和一个未分类的种是西瓜叶疫病的病原菌。
