Choi Jeong Ho, Kim Jong-Yea, Park Duck Hwan
Interdisciplinary Program in Smart Agriculture, Kangwon National University, Chuncheon 24341, Korea.
Department of Food Science and Biotechnology, Kangwon National University, Chuncheon 24341, Korea.
Plant Pathol J. 2022 Aug;38(4):355-365. doi: 10.5423/PPJ.OA.04.2022.0056. Epub 2022 Aug 1.
Erwinia amylovora and E. pyrifoliae are the causative agents of destructive diseases in both apple and pear trees viz. fire blight and black shoot blight, respectively. Since the introduction of fire blight in Korea in 2015, the occurrence of both pathogens has been independently reported. The co-incidence of these diseases is highly probable given the co-existence of their pathogenic bacteria in the same trees or orchards in a city/ district. Hence, this study evaluated whether both diseases occurred in neighboring orchards and whether they occurred together in a single orchard. The competition and virulence of the two pathogens was compared using growth rates in vitro and in planta. Importantly, E amylovora showed significantly higher colony numbers than E. pyrifoliae when they were co-cultured in liquid media and co-inoculated into immature apple fruits and seedlings. In a comparison of the usage of major carbon sources, which are abundant in immature apple fruits and seedlings, E. amylovora also showed better growth rates than E. pyrifoliae. In virulence assays, including motility and a hypersensitive response (HR), E. amylovora demonstrated a larger diameter of travel from the inoculation site than E. pyrifoliae in both swarming and swimming motilities. E. amylovora elicited a HR in tobacco leaves when diluted from 1:1 to 1:16 but E. pyrifoliae does not elicit a HR when diluted at 1:16. Therefore, E. amylovora was concluded to have a greater competitive fitness than E. pyrifoliae.
梨火疫病菌和梨疫病菌分别是苹果和梨树毁灭性病害的病原菌，即分别引发火疫病和黑梢疫病。自2015年韩国引入火疫病以来，已分别报道了这两种病原菌的发生情况。鉴于这两种病原菌在同一城市/地区的同一棵树或果园中共存，这两种病害同时发生的可能性很大。因此，本研究评估了相邻果园是否同时发生这两种病害，以及它们是否在同一个果园中共同发生。通过体外和植物体内的生长速率比较了这两种病原菌的竞争力和毒力。重要的是，当它们在液体培养基中共同培养并共同接种到未成熟苹果果实和幼苗中时，梨火疫病菌的菌落数显著高于梨疫病菌。在比较未成熟苹果果实和幼苗中丰富的主要碳源利用情况时，梨火疫病菌的生长速率也高于梨疫病菌。在包括运动性和过敏反应（HR）的毒力测定中，在群体运动和游动运动中，梨火疫病菌从接种部位的游动距离直径均大于梨疫病菌。梨火疫病菌在1:1至1:16稀释时能引发烟草叶片的过敏反应，但梨疫病菌在1:16稀释时不会引发过敏反应。因此，得出结论，梨火疫病菌比梨疫病菌具有更强的竞争适应性。
