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First Report of Fire Blight on Chinese Hawthorn (Crataegus pinnatifida) Caused by Erwinia amylovora in Korea

    Affiliations
    Authors and Affiliations
    • Y.-J. Lim1 2
    • H. Ham1
    • M.-H. Lee1
    • D. S. Park1
    • E. Roh1
    • D. H. Park2
    • Y. H. Lee1
    1. 1Crop Protection Division, National Institute of Agricultural Science, Rural Development Administration, Wanju 55365, Republic of Korea
    2. 2Interdisciplinary Program in Smart Agriculture, Kangwon National University, Chuncheon 24341, Korea

    Fire blight is one of the destructive plant diseases caused by Erwinia amylovora and causes enormous economic losses worldwide. Fire blight was initially reported in apples, pears, and Chinese quince (Myung et al. 2016a, b; Park et al. 2016) in Korea, but recent studies have reported new hosts such as apricot (Lee et al. 2021) and mountain ash (Lim et al. 2023). These reports indicate that fire blight is likely to disperse to new hosts in Korea. During the nationwide survey in June 2021, we observed typical symptoms of blossom blight and shoot blight on a Chinese hawthorn (Crataegus pinnatifida Bunge) plant near an orchard (37°09′21.7″N, 127°35′02.6″E) in Icheon, Gyeonggi Province, where fire blight of Asian pear occurred. For identifying its causal agent, bacterial isolates were recovered after incubating at 28°C for 24 h on tryptic soy agar (TSA) medium (BD Difco) from blighted leaves and shoots that were surface sterilized with 70% alcohol for 30 s and homogenized in 500 μl of 10mM MgCl2 buffer. Pure cultures of white to mucoid colonies were grown on mannitol glutamate yeast extract medium, a semiselective medium for E. amylovora. Two isolates produced a 1.5-kb amplicon through colony PCR using amsB primers (Bereswill et al. 1995). Two strains (CPFB26 and CPFB27) from the Chinese hawthorn produced amplicons identical to that from the TS3128 strain of E. amylovora, isolated from the pear tree and identified in 2016 (Park et al. 2016). For the partial 16s rRNA sequences, the total DNA of these two strains was extracted using the Wizard DNA prep kit (Promega, U.S.A.), and PCR was performed using fD1 (5′-AGAGTTTGATCCTGGCTCAG-3′) and Rp2 (5′-ACGGCTACCTTGTTACGACTT-3′) primer sets and further sequenced (Weisburg et al. 1991). These sequences belonged to the E. amylovora clade and were identified as E. amylovora in phylogenetic analysis (GenBank accession nos. OP753569 and OP753570). Based on BLASTn analysis, CPFB26 and CPFB27 showed 99.78% similarity to the sequences of the E. amylovora strains TS3128, CFBP 1430, and ATCC 49946. To confirm pathogenicity of the isolates, 10 μl of bacterial suspensions (1.5 × 108 CFU/ml) was injected through the veins of the upper second leaf of 3-month-old clones of apple rootstocks (Malus domestica cv. M29), and the rootstocks were incubated for 6 days at 28°C in a chamber with 12 h of light per day. Petioles and stems turned a red hue, and the shoots finally blighted. To complete Koch’s postulates, colonies were recovered on TSA medium from the inoculated apple rootstocks and verified through colony PCR for the amsB and A/B primer set (Powney et al. 2011). Hawthorn has been reported as an epidemiologically important alternate host plant of fire blight. This study is the first to report fire blight caused by E. amylovora in Chinese hawthorn in Korea. Because Chinese hawthorn is natively distributed in Korea and is widely used as a landscaping tree, the findings of this study suggest that early monitoring could prevent the spread of fire blight through natural hosts.

    The author(s) declare no conflict of interest.

    References:

    Funding: This work was supported by a grant from the Agenda program of the Rural Development Administration (PJ01505901), Republic of Korea.

    The author(s) declare no conflict of interest.