Identification of the Causal Agent of Bacterial Leaf Spot on Watermelon in China

    Authors and Affiliations
    • Pei Qiao1
    • Mei Zhao2
    • Dehua Liu3
    • Wei Guan1
    • Qingrong Bai3
    • Yuwen Yang1
    • Tingchang Zhao1
    1. 1State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
    2. 2Department of Plant Pathology, College of Plant Protection, China Agricultural University, Beijing, China
    3. 3College of Plant Protection, Jilin Agricultural University, Changchun, China

    Published Online:

    Watermelon diseases caused by pathogenic bacteria were endemic in Liaoning and Jilin Provinces from 2019 to 2020 in China, resulting in serious economic losses to the watermelon industry. This study characterized 56 strains isolated from symptomatic watermelon leaves collected from Liaoning and Jilin Provinces. Through morphological observation, 16S rRNA and gyrB sequence analysis, and BIOLOG profiles, the pathogen was identified as Pseudomonas syringae. In China, the watermelon disease caused by P. syringae was reported for the first time. The multilocus sequence analysis showed that the isolated strains belonged to three different clades within P. syringae phylogroup 2. Interestingly, most of them (79%) belonged to clade 2a, 14% were clade 2b, and 7% were clade 2d. This indicates that bacterial leaf spot outbreaks of watermelon in China were caused by multiple sources and mainly by P. syringae clade 2a.

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