Abstract
This studies were investigated the occurrence of sclerotinia rot at the crisphead lettuce field in Uiryeong-Gun, Gyeongsangnam-Do from January to May in 2003. Average incidence rates of sclerotinia rot on crisphead lettuce was up to 21.9% at the five plastic houses. A total of 140 isolates of Sclerotinia sp. were obtained from diseased leaves of crisphead lettuce. Among them, the fungi YR-1 was isolated, which showed highly virulent on the whole plant. the YR-1 was identified as Sclerotinia sclerotiorum based on the formation, color, shape and size of sclerotium and apothecium. For the pathogenicity test, the most suitable inoculum quantity of YR-1 strain was selected as the triturated mycelial suspension of $A_{550}$=0.8, 40 ml showing disease incidence of 94%, and the symptom showed as same as at the fields, the leaves and stem had rotten and developed white downy mycelial at the diseased lesion on the leaves and stems, and produced black and irregular sclerotinia. This is the first report on the pathogenicity test using by triturated mycelial suspension-inoculum of the pathogen for the sclerotinia rot of crisphead lettuce.
2003년 1윌부터 5월까지 경상남도 부림면 신반리의 결구상추 재배 플라스틱 하우스에서 자연발병된 균핵병의 발병율를 조사한 결과, 5.7%${\sim}$39.0%로서 평균 21.9%였다. 병든 밑둥부위에서 분리하여 병원성이 가장 강한 것으로 확인된 YR-1 균주를 형태 및 배양적 특성 등을 조사하여 기존의 보고와 비교한 결과 Sclerotinia sclerotiorum로 동정되었으며, S. sclerotiorum YR-1으로 명명하였다. YR-1 균주의 병원성 검정을 위하여 균사조각 부유액을 접종원으로하여 접종원의 최적 처리량과 최적 농도를 선발한 결과, 50%에 가까운 발병도를 보인 $A_{550}$=0.4와 0.6농도의 균사조각 부유액 40 ml로 선발하였다. 균사조각 부유액으로 병원성 검정 결과, 결구상추 재배 농가에서 자연발병된 병징과 동일한 병징이 나타났다.
