| Root-knot nematode(RKN,Meloidogyne spp.)with a wide host range is an economically most important plant parasitic nematode.RKN infects roots as a soil-born disease.Once RKN disease occurs in the field,it is difficult to eradicate.Chemical control is effective,but it is toxic to human and animal and unfriendly to environment.Therefore chemical control can not meet the need of sustainable development.Although other control methods,such as physical control,agricultural measures and resistance breeding can inhibit or decrease RKN damage to a certain extent,these applications also have their own limitations.Currently,biological control is the most potential control strategy based on sustainable development of green agriculture.In this study,7 soil bacteria isolated from soil and four symbiotic bacteria isolated from entomopathogenic nematodes were used.Through greenhouse pot tests and laboratory tests,the control effect of biocontrol bacteria against both M.incognita and M.hapla was demonstrated;the influence of these isolated bacteria and their metabolic products on egg hatching and nematode juvenile(J2)mortality of both nematodes was explored.The final goals were to screen highly effective biocontrol bacteria and to give an initial understanding of the the inhibiton mechanism,which will provide theoretical and applied basis for accelerating industrialization of the identified biological bacteria,In greenhouse pot experiments,the results indicated 10 ? dilution of symbiotic bacteria of entomopathogenic nematode Sf-IGA could reach 70.9% and 69.4% control effect on tomato cv.Zhongshu4 when infected by 1000 and 2000 M.incognita eggs/plant,respectively.Sf-IGA showed the highest contro efficacy among all other bacteria at these two inoculation dosages.However,the control effect showed less than 60% among four EPN symbiotic bacteria when tomato were inoculated with 5000 eggs/plant.With inoculation of 2000 M.hapla eggs/plant on tomato cv.Zhongshu4,the control effect of 10 x dilutions of symbiotic bacteria of EPN Sf-IGA(68.1%)?Hb-NJ(58.8%)?Hb-IGA(74.5%)had no significant difference between them and nematicides abamectin(78.6%).Soil bacterial strains B09 and B01 c produced 59~75% control effect on tomato cv.Zhongshu4 infected with 1000 and 2000 M.incognita eggs/plant,which had no significant difference with abamectin;While 10 x dilution of all 7 strains of soil bacteria agaist M.hapla on tomato cv.Zhongshu4 and VFNT showed 55.1-76.6% control effect with 2000 eggs/plant without significant difference from abamectin(86.9%).The results of labotorary experiments suggested that EPN symbiotic bacteria significantly affected M.incognita egg hatching.At 6 d,the 10 ? dilution of Hb-NJ symbiotic bacteria had the strongest inhibition effect on M.incognita egg hatching and the relative inhibition rate was 70.6%,but no effect with 20 x and 50 x dilution of symbiotic bacteria.The 10 x,20x and 50 x dilutions of EPN symbiotic bacteria had no impact on the M.hapla egg hatching and J2 mortality and M.incognita J2 mortality.The metabolic products of EPN symbiotic bacteria could inhibit both nematode egg hatching.The relative inhibition rate of 2x and 5x dilutions of metabolic products of EPN symbiotic bacteria reached up to 70% on both M.inconita and M.hapla egg hatching.Yet ther was no lethal effect on the larva of root knot nematode.The effective bacteria against RKN were identified through the amplification of 16 S rDNA sequences and the phylogenetic tree was constructed.The preliminary result indicated that Sf-IGA symbiotic bacteria was Xenorhabdus genus,symbiotic bacteria Hb-IGA was Photorhabdus genus,all 7 soil bacteria belonged to bacillus genus. |
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