Research On PGPR For Biological Control Against Soybean Cyst Nematode

PGPR induced soybean system resistance for biological control against soybean cyst nematode was screened and obtained.Taxonomy of PGPR,breeding of high-production strains and their fermentation conditions,effects of biological control,colonization of PGPR in soybean,action mechanism were studied systematically.The multifunctional preparation which increased soybean yield,optimized soybean qualty,induced soybean system resistance was manufactured.Results showed as follows:1.Soybean seeds coated by 1069 bacteria strains were grown on farmland which Heterodera glycines occurred seriously in Liaoning and Heilongjiang province.After 35 days, 14 strains showed efficiency to control soybean cyst nematodes.System resistance induced by antagonistic rhizobacteria was validated by the retrial in the second year.Five PGPR induced soybean system resistance were screened from farm and greenhouse experiments.They were Sneb207,Sneb353,Sneb364,Sneb382,and Sneb482.Sneb207 and Sneb482 showed strong and stable resistance between them.2.PGPR were classified and identified by the methods of classical morphological, biochemical and molecular biological taxonomy.The sequences of 16SrDNA gene were sequenced and analyzed.Results showed strains Sneb207,Sneb353,Sneb364,Sneb382,and Sneb482 belonged to Bacillus megaterium,Bacillus subtilis,Enterobacter cloacae, Enterobacter agglomerans and Bacillus megaterium,respectively.3.The multifunctional preparation was manufactured.Soybean seeds coated by sterilizing fermentation filtrates 207 and 482 were grown on farmland which Heterodera glycines occurred seriously in Liaoning and Heilongjiang province.The results showed both prepatations promoted soybean seedlings growth significantly,and induced soybean system resistance efficiently.And the inhibition rate against soybean cyst of soybean which treated by preparation was between 38.12%~82.13%.In different district,soybean which treated by preparation showed stable resistance to SCN.As SCN occurred more seriously,the resistance became more efficient.Also the multifunctional preparation could make soybean prematurity, increase soybean yield,optimize soybean quality.Such as pods and seeds per plant increased 100～300%,weight of seeds per plant increased 200～380%,weight of 100-seeds increased 14～40%and plant flesh weight increased compering with blank from.4.Breeding of high-production strains and their fermentation conditions were optimized. The fermentation conditions were investigated by single factor and designs of orthogonal experiments.And the results were as follows:the liquid medium of fermentation of strain Sneb207 constituded by sucrose 1.57%,beef extract 0.897%,yeast extract 0.842%.The fermentation conditions included the optimum initial pH8.0,2%of the inoculation amount, the volume of medium in shaking flasks about 40ml/100ml flask,rotate speed about 150r/min, all light cultivated at 28℃.And the liquid medium of fermentation of strain Sneb482 constituded by sucrose 1.51%,beef extract 0.836%,yeast extract 0.68%.The fermentation conditions included the optimum initial pH8.0,0.5%of the inoculation amount,the volume of medium in shaking flasks about 30ml/100ml flask,rotate speed about 150r/min,all light cultivated at 28℃.5.Marked PGPR Sneb207,resistant to erythromycin at 300μg/ml by continuously screening on series concentration of erythromycin media was obtained.The marked strain would be re-isolated from rhizosphere soil and soybean root when it was inoculated in the root.The result showed that Sneb207 could colonize,survive and transfer in soil and soybean root.The population peaks of marked 207 strains in rhizosphere soil,corm and pseudostem of soybean were at 15d after inoculation.The strain population showed the trend"increased at the beginning and decreased afterward"after inoculation.The result of the environment adaptability of Sneb207 on soybean rhizosphere showed that a new ecological equilibrium was set up by Sneb207,soybean,environment and rhizosphere microorganism.They composed an integrated system to improve the biological effect and stability of soybean resistance.And PGPR 207 could be used together with mostly germicides and fertilizer.So it could eradicate soybean root diseases by biological and chemical control.6.The mechanism how Sneb207 promoted soybean growth was studied.Sneb207 had the ability which fixed nitrogen and increased available P and K contents in rhizo-spheric soil. Sneb 207 as inner bacteria of soybean root could promote the root nodule forming,augment and enlargement.Sneb207 dissolved minerals,increased nutritious contents in rhizo-spheric soil.Sneb promoted soybean root growth,increased biomass,increased H~+-ATPase and decreased pH value in soybean root.So it adjusted soybean crucial physiological function and promoted soybean growth.7.The root split system test proved soybean system resistance was induced by Sneb207. The mechanism of soybean system resistance was studied by section using a cryostat.The micro-biology of root inoculated by sneb207 was changed.It manifested pericycle cells thickening and the structure tightening.So it held nematodes back effictively,confining them in phellem layer or exodermis.And the activities of defence enzymes of soybean root were enhanced after Sneb207 induced.