臺灣首次報導Ralstonia pseudosolanacearum引起龍鬚菜細菌性萎凋病

First report of Ralstonia pseudosolanacearum causing bacterial wilt of chayote shoots in Taiwan

2023年11月，在臺中市新社區的一處龍鬚菜栽培田區，發現植株呈現萎凋病徵，龍鬚菜罹病初期，部分葉片出現缺水症狀，葉片仍維持原有綠色，但葉表失去光澤，罹病嚴重植株則全株萎凋枯死。自罹病植株莖組織分離純化5株菌株RsCt1-RsCt5，並經由接種與再分離試驗，完成柯霍式準則。藉由16S rDNA基因序列進行菌種鑑定，結果顯示5株龍鬚菜菌株與已知Ralstonia pseudosolanacearum PLU-6菌株之16S rDNA基因序列，其序列相似度皆為100%（1,385/1,385 bp）。經菌株的生物型、演化型、序列型及厭氧硝酸鹽代謝等特性分析，結果顯示5株R. pseudosolanacearum的龍鬚菜菌株皆屬於第3生物型、第1演化型及第14序列型，且具有硝酸還原至氮氣產生的能力，為R. pseudosolanacearum菌種的特性之一。而對茄科作物的病原性測試結果，顯示龍鬚菜菌株同樣可以引起番茄、彩椒及茄子等植株萎凋。本研究證實葫蘆科作物龍鬚菜是R. pseudosolanacearum的新寄主植物，亦是R. pseudosolanacearum引起龍鬚菜細菌萎凋病之首次報導。

In November 2023, wilting symptoms were observed in the field of chayote shoots in Xinshe, Taichung. Initially infected plants look like wilting of some leaves for lack of water. Leaves keep their original green color but loss of gloss on the leaf surfaces. Severely infected plants wilted and died completely. Five bacterial strains (RsCt1-RsCt5) were isolated and purified from diseased stem tissues. Through inoculation and re-isolation tests, Koch's postulates were fulfilled. Species identification was performed by 16S rDNA sequence alignment. Results showed that all five strains of chayote shoots exhibited 100% sequence identity (1,385/1,385 bp) with the 16S rDNA sequence of Ralstonia pseudosolanacearum PLU-6 strain. Analysis of the strains' biovar, phylotype, sequevar, and anaerobic nitrate metabolism revealed that all five R. pseudosolanacearum strains isolated from chayote shoots belong to biovar 3, phylotype I, and sequevar 14. They also possess the ability to reduce nitrate to nitrogen gas and a key characteristic of R. pseudosolanacearum species. Pathogenicity tests on Solanaceae crops revealed that the R. pseudosolanacearum strains can also cause wilting on tomato, pepper, and eggplant plants. This study confirms that the chayote shoots of cucurbit crops is a new host plant for R. pseudosolanacearum and represents the first report of R. pseudosolanacearum causing chayote shoots bacterial wilt in Taiwan.