桑細菌性縮葉病

Abstract

2013年初春在宜蘭員山桑園發現葉緣及葉脈出現水浸狀，褐色至深褐色外圍具黃暈的不規則型斑點，嚴重時葉片皺縮且萎凋落葉，危害果實嚴重時也導致皺縮及落果，危害嫩枝條導致萎凋掉落。經組織分離及柯霍氏法則確認是由細菌所引起。病原菌經生理生化測定為Pseudomonas屬，利用對P. syringae group具專一性的引子對PsyF/PsyR進行PCR鑑定，供試已知的P. syringae菌株及供試桑菌株均產生144 bp專一性條帶，確認供試桑病原細菌屬 P. syringae group。進一步測試LOPAT與Biolog鑑定分析其特性結果與P. syringae pv. mori相符。再以16S rDNA定序鑑定後與GenBank中的P. syringae pv. mori序列比對(GenBank accession number AB001446.1)相似度達99％。綜合上述各項試驗，確認本病是由P. syringae pv. mori引起的細菌性縮葉病(bacterial blight)。初步室內篩選供試10種藥劑對桑病原細菌生長的抑制效果，確認供試的鏈四環黴素、多保鏈黴素及嘉賜銅對所有供試桑病原菌生長均有抑制效果，但鏈黴素對所有供試桑病原細菌生長則無抑制效果。 An unknown disease was noticed on commercial orchards of fruit mulberry (Morus alba) in Yuan shan（員山）, Yi-lan since 2013. The symptoms began with small watersoaked lesions with halo on the edge of the leaves, gradually became coalescence and caused leaf deformation. The infected fruits also showed black flecks initially, gradually flecks merged and fruit deformed and dropped. In severe case, the twig tips wilt and dry up. Koch's postulates were conducted and the results indicated that the disease is a bacterial cause. The causal agent was identified as Pseudomonas species using traditional physiological and biochemical tests. PCR tests indicated that tested isolates could generate a specific 144 bp fragment by using PsyF/PsyR primer pair that specific to P. syringae group. In addition, LOPAT and Biolog tests indicated that the bacterium is within P. syringae group especially similar to P. syringae pv. mori. In advance, the bacterium has proved to have 99% sequence similarity when compared with P. syringae pv. mori (AB001446.1) in Genebank by using 16S rDNA analysis. Furthermore, a preliminary chemical screening using ten commercial formulated agrochemicals found that streptomycin + tetracycline, thiophanate methyl + streptomycin and kasugamycin + copper oxychloride had better control efficacy in vitro.