萵苣細茵性葉腐病及品種抗性篩檢

Abstract

民國96~7年間於彰化縣芬園鄉種植之萵苣葉片上，出現不規則形褐化壞疽斑，病斑沿著葉脈擴散，嚴重時葉片呈現腐爛且破碎現象，中肋常被感染並造成褐化風輕微腐爛的病徵。由柯霍氏法則、生理生化及Biolog鑑定分析結果顯示供試萵苣病原菌株為Pseudomonas cichorii進一步應用對P. cichorii具有專一性之引子對進行PCR鑑定，結果顯示供試病原菌可增幅出379 bP之專一性DNA條帶，再以165 rDNA進行定序與比對分析鑑定，確認該病原菌為P. cichorii，依其引起之病徵將此病害定名為萵苣細菌性葉腐病(bacterial midrib rot of lettuce)。測定市售21種萵苣品種對萵苣細菌性葉腐病菌P. cichorii之抗性，結果顯示供試2種結球萵苣品種（捲心、包心以及7種葉萵苣品種（明豐3號、橡樹葉、人陸A、人陸妹、HV-076粉A、綠葉、翠花等）之萵苣植株於接種後均罹病死亡，其餘供試12種萵苣品種，包括1種結球萵苣、1種半結球萵苣、2種嫩莖萵苣及8種葉萵苣品種雖感病卻仍可持續生長，顯示其品種抗病性較佳。 An unknown bacterial disease was first found in lettuce cultivation areas of Changhua during summer of 2007 and 2008. Symptoms mainly occurred in the midrib of leaves and started with greenish, brown or black spots and later coalesced and developed leaf rot symptoms. Under humid condition, symptoms development could be rapid, often in less than 24 hours, and always occured on nearly mature plants before harvest. The causal agent was identified as Pseudomonas cichorii based on physiological and chemical tests, Biolog GN MicroPlate Identification System, 16S rDNA sequence analysis, and pathogenicity tests. The pathogen was further confirmed by PCR with SfL1 / SfR2 specific primers to Pseudomonas cichorii. This is the first report of the disease occurred on lettuce in Taiwan. In a disease resistance screening of the twenty one local lettuce cultivars, the result showed that all tested cultivars were sensitive to the disease but the romaine and stem lettuce showed moderate degree of resistance.