Biological control of root-knot nematodes by gelatinolytic bacteria = 젤라틴 분해 미생물을 이용한 뿌리혹 선충의 생물학적 방제

국문 초록 (Abstract)

젤라틴 분해 특성을 가진 박테리아를 근권토양으로 부터 분리하였으며16S rRNA gene sequence analysis에 의해 Bacillus luciferensis, Enterococcus sp. 및 Bacillus megatirium 으로 동정하였다. Bacillus luciferensis는 protease를 생성함을 확인하였으며 나머지 두 균주는 HCN 및 proteases를 생성함을 확인하였다. 분리 된 3종의 박테리아의 처리는 Meloidogyne incognita 의 암컷 세포벽을 분해함으로써 몸체를 파괴함을 확인하였다. B. luciferensis, Enterococcus sp. 및 B. megatirium 를 처리한 토마토는 무처리구와 비교할 때 더 큰 초장과 생체중을 보였고 2기 유충, 난낭 및 뿌리혹지수는 더 낮은 값을 나타내었다. 또한 Enterococcus sp. 의 처리는 가장 강한 항 선충 활성을 나타내었다. 따라서 Enterococcus sp. 를 선정하여 부식된 톱밥 및 키틴퇴비와 혼합하여서 선충 방제 효과를 검증 하였다.
Gelatin을 기질로 한 액체배지에서 84시간 배양 후 Enterococcus sp. 의 gelatinase 활성은 48.6 ㎕/ml에 도달하였으며 높은 gelatinase활성은 120시간까지 유지되었다. 노출된 환경에서의 대량배양에서도 미생물의 밀도 및 gelatinase 활성은 2.8 × 108 CFU 및 40.2 ㎕/ml 의 수치를 나타내었다.
Cadusafos 를 처리한 근권 토양에서 2기 유충의 밀도는 composted sawdust + Enterococcus sp. 처리 및 composted sawdust처리에 비해 낮은 반면, 뿌리 중 eggmasses는 더 높았다. composted sawdust + Enterococcus sp. 의 처리는 가장 높은 초장과 생체중을 보여주었다. 또한 cadusafos처리, composted sawdust + Enterococcus sp. 처리, composted sawdust처리에 비해 무리처구의 토마토 뿌리는 언제나 많은 H₂O₂ 를 생성 하였다. 실험의 후반부에서 cadusafos및 무처리구에서 토마토 잎이 황화 되고 시들음 증상을 보였으나 composted sawdust + Enterococcus sp. 및 composted sawdust 처리구에서는 정상적인 생육을 보였다.
상추 정식 후 50일째에 Enterococcus sp. + chitin compost 처리구에서 건물중과 엽면적 모두 가장 높은 값을 보였으며 cadusafos처리구는 뿌리에서 eggmass, egg 및 2기 유충의 밀도가 가장 낮은 수치를 나타냈다. 비록 cadusafos 보다는 낮은 항선충 활성을 보였지만 Enterococcus sp. + chitin compost 처리구는 대조구에 비해 eggmass, egg 및 2기 유충을 각각 60.7%, 86.3% 및 72.2% 감소시켰다.

다국어 초록 (Multilingual Abstract)

Three gelatinolytic bacteria possessing a strong ability in liquefying gelatin were isolated from rhizosphere. Based on the 16S rRNA gene sequence analysis, the bacteria were identified as Bacillus luciferensis, Enterococcus sp. and Bacillus megatirium, respectively. All of the bacteria were regarded to produce gelatinase, protease and hydrogen cyanide (HCN), except Bacillus luciferensis which do not produce HCN. Bodies of Meloidogyne incognita females were completely destroyed in the presence of each bacterium. In the pot trails, second stage juveniles, eggmasses and gall index were lower in the plants grown in the gelatinolytic bacteria amended treatments where the populations of the gelatinolytic bacteria was greater than control at each time point. Furthermore, amendment of tomato plant with B. luciferensis, Enterococcus sp. and B. megatirium promoted plant growth in shoot length and fresh weight compared to control treatment.
Gelatinase activity of the Enterococcus sp. which showed the strongest nematicidal activity was reached to 48.6 μl/ml in a minimal medium containing gelatin as sole carbon source. Enterococcus sp. was combined with the composted sawdust which contained abundant phenolic compounds or chitin compost to develop an effective bioformulations. Eggmasses in roots were higher, while second stage juveniles in rhizosphere at cadusafos were lower compared to composted sawdust + Enterococcus sp. and composted sawdust. However, highest shoot length and fresh weight were found in composted sawdust + Enterococcus sp. during the study period. Throughout the experiment, H₂O₂ production in control was always higher than cadusafos, composted sawdust + Enterococcus sp. and composted sawdust. At the end of experiment, tomato plant leaves in cadusafos and control turned yellow and drooped; however, plants in composted sawdust + Enterococcus sp. and composted sawdust treatments appeared to be normal.
Furthermore, both the shoot dry weight and leaf area in the lettuce plant increased mostly by the amendment of Enterococcus sp. with chitin compost at 50 days after transplanting. Although the eggmasses, eggs in root and second stage juveniles in rhizosphere was lowest in cadusafos, those in Enterococcus sp. + chitin compost were reduced by 60.7%, 86.3% and 72.2% compared to control.
This study is the first report in control of root-knot nematodes by gelatinolytic bacteria. These results indicate the potential of gelatinolytic bacteria to alleviate nematode parasitism in important vegetable crops.

목차 (Table of Contents)

• Abstract = 7
• General Introduction = 9
• 1. Root-knot nematode = 9
• 2. Life cycle = 10
• 3. Control of root-knot nematode = 11
• References = 16
• Chapter Ⅰ: Biological control of Meloidogyne incognita by gelatinolytic bacteria in tomato = 21
• Abstract = 21
• Introduction = 22
• Materials and Methods = 25
• Results = 31
• Discussion = 41
• References = 44
• Chapter Ⅱ Effect of gelatinolytic bacteria and composted sawdust on the reproduction of Meloidogyne sp. in tomato = 49
• Abstract = 49
• Introduction = 50
• Materials and Methods = 52
• Results = 55
• Discussion = 63
• References = 66
• Chapter Ⅲ Efficacy of gelatinolytic bacteria and chitin compost amendment against Meloidogyne sp. infecting lettuce = 71
• Abstract = 71
• Introduction = 72
• Materials and Methods = 75
• Results = 78
• Discussion = 83
• References = 87
• General Conclusions and Perspectives = 92
• 초록 = 94