Identification and Pathogenicity of Binucleate Rhizoctonia Isolates Causing Leaf Blight(Yellow Patch) in Turfgrass

잔디의 잎마름증상(Yellow patch)을 일으키는 2핵성 Rhizoctonia의 동정 및 병원성

Yellow patch as leaf blight caused by binucleate Rhizoctonia occured in bentgrass (Agrostis Palustris Huds), zoysiagrass (Zoysia japonica Steud) and Kentucky bluegrass (Poa pratensis L.) from several golf couses in Korea. Binucleate Rhizoctonia was isolated from the infected lesions and was identified Rhizoctonia cerealis. Rhizoctonia cerealis infected crown, stem and leaf tissue, and the symptom was light yellow circular patch upto 1 m in diameter on bentgrass golf green. Individual infected leaf near the margin of patch developed first red and finally turn brown. As zoysiagrass lawn, the symptom was 30~40cm circular patch that occured zoysiagrass shooting time as spring, and there could not sheeted in severe lesion. In case of sheeted, zoysiagrass was first irregular leaf sopt and finally dead. Hypha diameter of Rhizoctonia cerealis was $2.5~6.3\mu\textrm{m}$(average $3.8\mu\textrm{m}$) and colar was white to buff. Monilioid cell size was $5.8~12.5$\times$13.8~37.5\mu\textrm{m}$. Sclerotia size was 0.2~2.0mm and color was white to brown. Optium temperature for the hypha growth was $23^{\circ}C$. There was a little difference in pathogenicity among the isolates.

국내 골프장에 식재된 bentgrass (Agrostis palustris Huds), zoysiagrass (Zoysia japonica Steud) 및 Kentucky bluegrass (Poa pratensis L.)에 잎마름증상(yellow patch)을 나타내는 병반 부위에서 병원균을 분리ㆍ동정한 결과 2핵성인 Rhizoctonia cerealis로 동정되었다. 병원균은 잔디의 관부와 엽조직을 침해하였으며, 병징은 bentgrass의 경우 1m 내외의 둥근 고리모양의 병반을 형성하고, 병반 가장자리의 잔디잎은 초기에는 붉은색을 띠며 병이 진전됨에 따라 갈변하였다. Zoysiagrass에는 직경 30~40cm의 근사원형의 병반이 봄철 맹아시기에 발생하고, 병반 부위에서는 잔디가 맹아되지 않았다. 맹아된 잔디에는 부정형의 볏짚색 반점이 생기면서 고사되었다. Rhizoctonia cerealis의 균사직경은 2.5~6.3$mu extrm{m}$(평균 3.8$\mu\textrm{m}$)이었으며, 균사는 담황색을 띠고, 균총의 색은 밝은 갈색을 나타냈다. Monilioid cell 크기는 5.8~12.5$\times$l3.8~37.5$\mu\textrm{m}$였으며, 배지상에서 형성된 균핵의 크기는 0.2~2.0mm, 균핵의 색은 처음에는 흰색을 띠다가 성숙해가면서 갈색을 나타냈다. 온도에 따른 균사의 생장은 23$^{\circ}C$에서 가장 양호했다. 병원성 검정 결과 분리균간에 병원성에는 다소 차이가 있었다.