2018年3月於彰化縣田尾鄉之宮粉仙丹葉片上,發現中央褐色壞疽且周圍具黃色暈環之葉斑型病徵,切取罹病葉片組織,置於光學顯微鏡下可觀察到細菌菌流,經分離純化獲得14株病原細菌。所得菌株於NA平板培養基上呈黃色黏稠狀菌落,為革蘭氏陰性、好氧性細菌,可於菸草葉片誘導產生過敏性反應,以10^5 CFU.ml^(-1)細菌懸浮液噴霧接種於宮粉仙丹,可呈現與田間相同之病徵。利用生理生化特性測試及gyrase B序列分析鑑定為Xanthomonas axonopodis pv. maculifoliigardeniae。本病害在臺灣尚無推薦藥劑,以田間栽培常用藥劑進行測試,顯示以12.5%鏈黴素溶液及10%鏈四環黴素水溶性粉劑等抗生素類藥劑之抑制能力最佳。
Ixora(Ixora x westii)plants exhibiting brown and necrotic lesions surrounded by a wide chlorotic halo were observed in March, 2018, at Tianwei Township, Changhua County in Taiwan. Microscopic examination showed that masses of bacterial cells oozed out of the freshly cut tissues from the junctions of diseased and healthy area of lesions. The bacteria formed yellow and mucoid colonies on NA medium. Results of Gram staining showed that the isolated bacterial cells were Gram-negative. Fourteen bacterial strains were characterized as Xanthomonas axonopodis pv. maculifoliigardeniae with phylogenetic analysis of gyrase B sequences. All of bacterial suspensions(10^5 CFU.ml^(-1))were prepared individually from these 14 strains and sprayed onto 4-week-old Ixora plants. Brown and necrotic lesions surrounded by a wide chlorotic halo as the field-grown Ixora plants were observed. Bacteria isolated from the inoculated Ixora leaves showed the same cultural and biochemical characteristics as the bacterium originally isolated from the field samples. Subsequently, the sensitivity of the bacterial strains to multiple commercial fungicides was tested, and the results showed that the bacterium was most sensitive to streptomycin(12.5% SL)and streptomycin + tetracycline(10% SP).
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