Biocontrol Of Root-knot Nematodes, Meloidogyne Spp.on Vegetables By PGPR Strains

Root-knot nematodes (Meloidogyne spp.) are a major group of pathogens of agricultural crops worldwide and have been listed as quarantine pests in many countries. These root parasites pose a crop losses due to root-knot nematodes have been increasing make great threat to the production of vegetables and fruits in China.Because of the fast development of greenhouse vegetable production. Chemical control of root knot nematodes are harmful to human beings, domestic animals and environmental ecology, which limited the use of these products for disease control. Using plant growth promotion rizhobacteria (PGPR) for plant disease control is becoming an effective and available choice.Two bacteria strains NJ08 and NJ218, isolated from soils infected with root knot nematodes, were analysed by biological, physiological methods, and 16S rDNA sequences. NJ08 was identified as Bacillus cereus and NJ218 was similar with Bacillus pumilus in biological, physiological and biochemical characters. The ribosomal 16s rDNA of these two strains were amplified and the PCR products were sequenced. Sequence comparison, NJ08 is 100% identical to Bacillus cereus and NJ218 99% identical to with Bacillus pumilus.A biocontrol preparation (GJ23) composing mixtures of NJ08 and NJ218 was assayed in vitro for effect on M. incognita. The GJ23, NJ08 and NJ218 were evaluated for their ability to control root-knot nematode M. incognita in greenhouse pot tests and small field tests.Bacteria suspension and supernatants of fermented GJ23 were used for treatments of M. incognita eggs and second stage juveniles (J2) in vitro assayes. Different diluted concentrations of GJ23 inhibited the movement of J2, but increased the hatching of eggs.Greenhouse pot tests showed that treatments with GJ23,NJ08 and NJ28 have greatly inhibited gall formation on tomato roots. Compare to control treatments, double-diluted bacteria suspension treatments decreased average gall numbers 51.4%, 62.5% and 54.5%, respectively , increased plant crown weight...