Root-Knot Nematode Disease Investigation In Jiangsu Province And Its Antagonistic Microbical Screening

Plant parasitic nematodes are soil pathogens that endanger crops and vegetables,and cause serious economic losses.Due to rapid economic development and globalization of trade,plant nematode disease has been widely distributed around the world.Nematodes live in the soil,which is difficult to control and frequently associated with bacterial or fungal disease.Plant parasitic nematodes could be rapidly and effectively controlled through chemical control method.Environmental problems produced by chemicals stimulated the research for alternative control strategies.In the present study,a total of 76 fields from Xuzhou,Suqian,Huai'an,Yancheng,Yangzhou and Nanjing in Jiangsu provice were investigated on the occurrence of root-knot nematode diseases.The disease rate was 59%.Except cotton,vegetables,peppers,peanuts and eleusine indica,root-knot nematode diseases happened on cowpea,cucumber,cabbage,amaranth,watermelon,eggplant,tomato,catalpa tree and catalpa.We collected root-knot nematode from the diseased tissue,and purified the root-knot nematode from eggplant,amaranth and cucumber,which was identified as Meloidogyne incognita.We collected the rhizosphere soil from the investigated fields,to investigate the control effect of soil suspension on the M.incognita.The results showed that the soil suspension of healthy eggplant collected from Liuhe,Nanjing,could significantly reduce the galls of tomato plants caused by M.incognita.The average root galls decreased by 55%;the galls was also reduced by 48%when the microbes of the rhizosphere of eggplant soil were filtered.We further isolated the bacteria and actinomycetes of the eggplant rhizosphere soil,and tested the protease,cellulase,chitinase activity and siderophore-containing of these isolates.5 stains of bacteria and 10 stains of actinomycetes were selected for antagonistic test in vitro and greenhouse assay.We found that the mortality of J2 reached 100%at 12 h,after exporure to the supertatant of bacteria Jdnl and actinomycetes A22,respectively.In tomato plant pre-treated with strain Jdnl,the galls of treated plants were significantly reduced by 26%when comparing to the H2O-treated plants.However,the galls of A22 filtration treated plants did not show any significant differences when comparing to the control.The results showed that Jdnl cell culture and its supernatant could significantly reduce the number of M.incognita when compared with that of the control,which reduced by 33%and 87%,respectively.The reproductive ability of M.incognita was remarkable reduced 38%by strain Jdnl.According to the colony morphology,physiological and biochemical characteristics,and 16S rRNA sequencing,Jdnl was identified as Pseudomonas sp..