Preservation Methods of Xanthomonas campestris pv. oryzae in Relation to Virulence and Colony-Type Variation

벼 흰빛잎마름병균의 균주보관에 따른 병원성 및 집락변이현상

Effects of presservation methods on viability and virulence of Xanthosmonas compestris pv. oryzae were investigated. The incidence of colony-type variants from freeze-dried and deep-frozen cultures was also determined. The suspending medium for freeze-dried cultures containing $10\%$ sucrose and $1\%$ gelatin showed the highest viability, and the virulence was well maintained in the suspending medium containing $2\%$ dextrin, $0.5\%$ ascorbic acid, 0.5% ammonium chloride, $0.5\%$ thiourea, and $0.85\%$ NaCl. Serially transferred cultures became attenuated. Rough colonies which had wrinkled surface occurred at a frequency of $1.9\%$ to $15.8\%$ during freeze-drying and freezing. The rough colonies consisted of nonseptated filamentous cells and rod-shaped cells. The virulence of rough colonies was weak as compared with the normal colony type.

벼흰빛잎마름병균의 균주를 효과적으로 보관하기 위하여 동결건조, 동결, 액체파라핀, 살균수, 계대배양등의 방법을 사용하여 생존율과 병원성유지 정도를 4개월에 걸쳐 조사하였다. 실험결과 $10\%$ sucrose와 $1\%$ gelatin을 함유한 현탁액에서 가장 높은 생존율을 나타냈으며 병원성은 $2\%$ dextrin, $0.5\%$ ascorbic acid, $0.5\%$ ammonium chloride, $0.5\%$ tguiyrea, $0.85\%$ NaCl 등을 함유한 현탁액에서 가장 잘 유지되었다. 계대배양한 균주는 병원성이 약화되었다. 거친집락형은 동결건조 또는 동결과정에서 모두 나타났으며 이는 정상집락에 반해 주름진 집락모습과 사상형이었다. 거친집락형은 병원성이 매우 약하였으며, 탄소원 요구도가 다양하였으므로 동결건조 과정에서 대사작용의 저해가 일어난 것으로 추측되었다.