Abstract
A infectious fungus (J131) recently isolated from artificial cultivation farms of Paecilomyces tenuipes is known to cause a great yield loss and deterioration of products. In this study, its occurrence and characterization were made. The isolate (J131) was identified as Paecilomyces farinosus (Holm ex S. F. Gray) Brown ＆ Smith. Colonies of the isolate on PDA grew moderately fast, attaining a diameter of 19mm within 14 days at 24${\pm}$1$^{\circ}C$. Vegetative hyphae are smooth-walled and hyaline. Conidiophores mainly arose from the submerged mycelium, usually measuring 1.3-1.5$\mu\textrm{m}$ wide and consisted of verticillate branches with whorls of 2 to 4 phialides. Phialides of 3.8-5.8${\times}$1.5-1.8 $\mu\textrm{m}$, with a swollen basal portion tapered into a distinct neck of about 0.6-0.8 $\mu\textrm{m}$ wide. Conidia arisen from the phialides, were ellipsoidal to fusiform, smooth-walled, hyaline, 1.8-2.4${\times}$1.1-1.4$\mu\textrm{m}$. .When silkworm larvae were injected with concentration of 1${\times}$10$\^$8/ conidia/$m\ell$ of infectious fungus J131, infection rate was 41.3％ and synnemata formation rate was 23.6％. Black spots were appeared on the surface of silkworm larvae in 5-9 days after injection. The surface of larvae was covered with hyphae which were gradually turned into yellow from white color during the incubation period of 3-4 days. 1 to several 4-6mm long synnemata of yellow or orange color were formed on the surface. The matured synnemata were ramified from its end and produced much conidia of white color.
전라북도 동충하초 재배농가 오염균은 Paecilomyces farinosus(Holm ex S. F. Gray) Brown ＆ Smith로 동정되었으며 특성은 다음과 같다. 분리$.$균은 감자한천배지 상에서 24$\pm$1$^{\circ}C$, 14일간 배양한 결과 배지 앞면은 흰색, 뒷면은 노란색을 띠고 직경 19mm로 생장하였다. 균사 직경은 1.2-1.9$\mu\textrm{m}$이며 분생자병은 투명하며 직경 1.3-1.5$\mu\textrm{m}$이다. phialides는 윤생형으로 분생자병으로부터 2-4개가 형성되며 기부는 부풀어 있고 상단부로 갈수록 폭이 좁아지는 호리병형으로 3.8-5.8${\times}$1.5-1.8$\mu\textrm{m}$이다. phialides의 neck은 직경 0.6-0.8$\mu\textrm{m}$이며, 분생 포자는 분생자형성세포로부터 연쇄상으로 발생하며 타원형 혹은 방추형이며 크기 1.8-2.4${\times}$l.1-1.4$\mu\textrm{m}$이다. 균 농도 1${\times}$$10^{8}$ conidia/$m\ell$로 경피 접종된 누에의 감염률은 41.3%이었으며, 분생자병속 형성률은 23.7%이었다. 균 접종 5-9일 후 누에피부 상에 검은 반점이 형성되었으며, 보호기간 3-4일 후 감염누에 표피는 흰색의 균사에서 점차 노란색 균사로 덮이며, 분생자병속이 발생되었다 분생자병속은 노란색, 선단부로 갈수록 흰색을 나타내었으며 4-6mm 길이로 표피에 한 개에서 다수가 형성되었다. 또한 성숙된 분생자병속의 끝부분에는 분지 후 흰색의 분생포자가 다량 발생하였다.
