Chemotaxis Of Two Kinds Of Nematodes Induced By Rhizosphere Bacteria

The study showed that the rhizosphere bacteria had chemotaxis effects on the nematodes. Rhizosphere bacteria can produce volatile substances, as signal factors to attract or repel nematodes. In this paper,391 strains of rhizosphere bacteria were screened for the chemotaxis of Caenorhabditis elegans. Twenty one strains were selected to test the chemotaxis of Meloidogyne incongnita and C. elegans, and six of them were identified. Volatile compounds of these strains were identified by gas chromatography/mass spectrometry technology. Some compounds were selected for verification. The main results are as follows:Three hundreds and ninety-one rhizosphere bacteria were selected to test the chemotaxis of the C. elegans. Twenty one strains showed high activity, relatively.The chemotaxis of the M. incognita and the C. elegans of the active 21 strains were determined. The chemotaxis index of 9 strains were negative, the other nine strains were between 0 and 0.2, and index of two strains is greater than 0.2. Index of strain 5-14 was the highest, up to 0.41. All chemotaxis index of M. incognitais is positive. There are 4 strains above 0.2. The highest is strain 2-35, reaching 0.36. Six selected strains, which chemotaxis index of M. incognita or C. elegans were greater than 0.2 were identified. They were Bacillus sp., B. amyloliquefaciens, Brevibacillus brevis. B. cereus. B. megaierium and Chiyseobacterium indologens.The volatile compounds produced by six selected strains were identified by GC-MS, and 67 kinds of volatile compounds were detected, including 10 kinds of alkane,5 kinds of alkene,13 kinds of ketones,3 kinds of aldehydes,9 kinds of nitrogenous,5 kinds of acids,9 kinds of esters,4 kinds of alcohols,4 kinds of benzene ring,1 ethers,2 phenols,1 containing sulfur and 1 containing bromine.Pure products tested results show that:Benzeneacetaldehyde(105 ppm、104 ppm), 2-Nonanone(103 ppm), Hexanal(105 ppm、104 ppm、103 ppm), Furfural(106 ppm、105 ppm、104 ppm), Benzaldehyde(104 ppm), Beta-butyl ester(106 ppm),Pyrazine, 2,5-dimethyl-(105 ppm) and lndole(105 ppm) have attractive effect on C. elegans. Decanal(103 ppm),2-Nonanone(106 ppm、105 ppm、104 ppm) and Pyrazine, 2.6-dimethyl-(105 ppm) have strong repellence to C. elegans. Decanal(103 ppm) and trans-2-Hexenal(104ppm) have attractive effect on M. incognita.Highlight of this research:1. Bacillus cereus and B. megaterium were proved to be attractive to the M. incognita. Bacillus sp., B. amyloliquefaciens, Brevibacillus brevis and Chryseobacterium indologens were proved to be attractive to the C. elegans.2. The effect of volatile products of the rhizosphere bacteria on the chemotaxis of nematodes were confirmed, and several related compounds were identified.