Abstract
Three post-harvest fields each in four rice growing areas, Iri, Naju, Jinju and Taegu were randomly selected and surveyed during December 1986 to examine sclerotial density of Rhizoctonia solani overwintering in the field. Surface soil of $0.09m^2$ area was sampled in each field with three replications and sieved to collect sclerotia. Germiability and pathogenicity of collected sclerotia were examined in the laboratory. Number of sclerotia $({\times}10^6)/ha$ in Iri, Naju, Jinju, and Taegu was estimated from the sample as 2.7, 1.2, 0.7 and 0.6, respectively. Based on sample variance with simple random sampling in each area, number of sampling required for estimating average sclerotial density with the precision of 10% apart from a chance of 1 in 20 was calculated to 41, 132, 232, and 395 for Iri, Naju, Jinju and Taegu, respectively. Percentage of germination of sampled sclerotia on potato sucrose agar (PSA) ranged from 42 to 78% depending on the area, and averaged 60%. About 49% of the germinated sclerotia were pathogenic to a rice cultivar Jinheung that was used to test pathogenicity of the sclerotia. Proportion of viable sclerotia that have both germiability and pathogenicity was thus estimated to 0.29 of total sclerotia collected. R. solani cultures obtained from the sclerotia could be distinguished into three groups based on colony morphology on PSA. Size and number of sclerotia formed on PSA differed between group but were not associated with pathogenicity to Jinheung.
포장(圃場)에서 월동(越冬)하고 있는 벼 잎집무늬마름병균(病菌) 균핵(菌核)의 밀도(密度)와 그 활성(活性)을 조사(調査)하기 위하여 1986년(年) 12월(月)에 이리(裡里), 나주(羅州), 진주(晋州), 대구(大邱)의 포장(圃場)에서 균핵(菌核)을 채집(採集)하여 발아력(發芽力)과 병원성(病原性)을 조사(調査)하였다. 균핵(菌核)의 밀도(密度)는 이리(裡里), 나주(羅州), 진주(晋州), 대구(大邱) 지역(地域)이 각각(各各) ha당 $2.7{\times}10^6,\;1.2{\times}10^6,\;0.7{\times}10^6,\;0.6{\times}10^6$였으며 지역(地域)에 따라 그중 $42{\sim}78%$(평균(平均) 60%)가 발아력(發芽力)이 있었고 발아(發芽)된 균핵중(菌核中) 평균(平均) 49%가 벼품종(品種) 진흥(振興)에 병원성(病原性)이 있었다. 따라서 발아력(發芽力)과 병원성(病原性)을 동시(同時)에 가진 균핵(菌核)의 비율(比率)은 전체균핵(全體菌核)의 29%였다. 균핵(菌核)으로부터 분리(分離)한 잎집무늬마름병균(病菌)은 배지(培地)에서의 균총형태(菌叢形態)에 따라 3가지 유형(類形)으로 대별(大別)되었으나 유형(類形)이나 균핵(菌核)의 크기, 균핵형성량(菌核形成量)은 진흥(振興)에 대(對)한 병원성(病原性)과 아무런 상관(相關)이 없었다. 10%의 편차(偏差)안에서 평균균핵밀도(平均菌核密度)를 95% 신뢰(信賴)하기 위하여 필요(必要)한 단순임의(單純任意) 표본수(標本數)는 이리(裡里), 나주(羅州), 진주(晋州), 대구(大邱)에서 각각(各各) 41, 132, 232, 395개소(個所)로 산출(算出)되었다.