Study On Fermentation Conditions Of Photorhabdus NJ And Effect On Soybean Cyst Nematode

Symbiotic bacteria Photorhabdus sp.NJ was found to show high nematicidal activities to Hetero- dera glycines which was isolated from Heterorhabditis. In order to develop the strain further, in this paper, the strain was identified and the fermentation conditions,the virulence in the lab and the pot efficacy to the soybean cyst nematode were researched.The primary results are as follows:1. In laborary virulence tests, The effect of NJ metabolites on eggs hatching and juveniles of Hete- rodera glycines were investigated.The results indicated that the hatching rates of eggs were strongly inhibited by original and 5×diluted solution .The effect of fermentation to J2 was obvious than the eggs. The mortality of J2 increased over time. After 72hours, the corrected mortality rate of J2 were100% treated with original,5×and 10×, even the teatetment dealed with 50×reach to 63.82% .2. The effect of some fermentation factors on the production of antibiotic substances was analyzed. The production of antibiotic substances was consistent with the bacterial growth.The medium of TSY and YSG are best for the growth of NJ and the production of metabolites. pH of medium from 6.0~8.4 has no influence to the strain. The seed culture of 24h was benefit to the production of antibiotic. There was no siganificant difference on it when the inoculum size varied from 1%~10% (V/V).3. The strain of NJ was identified by moleculer biology method to amplified the sequence of 16S rDNA and abtained a fragment with 466bp in the end . The homology was analyed with DNAstar, The phylogenetic tree obtained by the neighbour joining method.The result showed that strain NJ clustered together with those of Photorhabdus temperata. On the basis of the 16S rDNA sequence analysis, strain NJ may belong to the species of P. temperata.4. Pot experiments were carried out to study the effect of biocontrol strain NJ on the growth of soybean and controlling efficacy to soybean cyst nematode. The results showed that the adequate NJ fermentation can stimulate the growth of soybean and inhibit the occurence of Heterodera glycines effectively. But the efficacy was related to the treated methods,the amount of inoculum,the inoculum period and the concentration.