Biological control of the root-knot nematode, Meloidogyne hapla with an antagonistic bacterium

Bacillus cereus;biological control;Meloidogyne hapla

농업생명과학대학 농생명공학부 ;

University:서울대학교 대학원

关键词: Bacillus cereus;    biological control;    Meloidogyne hapla;   

Others  :  http://s-space.snu.ac.kr/bitstream/10371/125795/1/000000009128.pdf

美国|英语

来源: Seoul National University Open Repository

【 摘 要 】

however, M. hapla favors rather cool temperature, widely distributing in crop fields such as ginseng and carrot. Up to this day, chemical control using nematicides has been often used for the control of the nematodes, which is not enough to achieve a full control because of their soil-borne nature. Besides, chemical nematicides are very toxic to humans, animals and sometimes even to plants, and bring about soil and water pollution. Biological control is a good alternative for the chemical control, providing an efficient control value with no or little hazards to soil environments. Thus, the purpose of this study is to investigate biological control of the root-knot nematode (RKN), M. hapla that damages severely the root crops in fields using an antagonistic bacterium. Root-knot nematodes used in experiments were isolated from root galls of ginseng cultivated in Jinan, Korea and identified Meloidogyne hapla through 28S rDNA sequencing analysis. To find useful antagonistic bacteria against M. hapla, soil samples were collected from various regions and bacteria were isolated through the dilution plating method. Out of 523 bacterial isolates from soil samples and 19 Paenibacillus strains isolated from ginseng roots, a bacterial isolate C1-7 showed a very strong nematicidal activity in vitro against M. hapla. In pot experiment on tomato and carrot inoculated with the root-knot nematodes, treatments of C1-7 bacterial culture (1×108 CFU/㎖) reduced root-galling with control values of 100 % and 90 % and egg mass formation with control values of 75 % and 100 %, respectively, compared to those on plants only with RKN inoculation, and the bacterial treatments alone showed no evident phytotoxicities to both plants. The bacterial isolate formed circular and flat colonies with undulate margin, and was rod shaped bacilli and gram-positive, which was identified Bacillus cereus by the morphological characters, and Biolog program, fatty-acid composition and 16S rDNA sequencing analyses. Population density of C1-7 were kept high for a long period of time and its nematicidal activity was strong when it was cultured in brain heart infusion broth, compared to other culture media such as nutrient broth, Luria Bertani broth and tryptic soy broth. Culture filtrate of C1-7 from 48-h culture with or without heat treatment showed strong nematicidal activity even at a concentration of 1 %. Light microscopy of RKN-infected root tissues treated with C1-7 showed the inhibition of intact giant cell formation, sometimes accompanying dead nematodes located in the root tissues, while RKN alone induced fully matured giant cell formation with profound cell wall ingrowths. All of these results suggest the C1-7 bacterial isolate have a good potential to be developed as a biocontrol agent for the root-knot nematode, M. hapla.