Promoting Effects Of Bacterial-Feeding Nematode On Plant Growth-Promoting Bacteria In Soil

This study was mainly for the utilizable phosphorous release in the fluvo-aquic soil and stimulating the plant growth; IAA-producing strains were isolated from fluvo-aquic soil, out of which the strain JX15showed the highest and most stable IAA excreting ability (22.55μg/ml in20h cultivation), combining additional phosphate-dissolving capability as well. Based on morphological, part of the physiological and biochemical characteristics and16S rRNA sequences analysis, it was identified as Bacillus megaterium (GenBank Accession No. JX424613). Single factor tests were designed for preliminary study of the optimized conditions for the strain growth and fermentation. Results showed that the optimum condition for growth was consistent with that for excretion. The optimal culturing conditions for both growth and IAA secretion were pH7-8, filling volume50ml/250ml flask, incubation at30℃for24h, the best carbon and nitrogen sources were mannit and yeast extract. These results provided the experimental basis about the strains for the development of bio-organic fertilizer in the future.In gnotobiotic microcosm experiment, the results showed that:Grazing on bacteria stimulate the growth of the bacteria; however, grazing on bacteria stimulated bacteria activity and the ability of producing IAA significantly. They were influenced by nematodes species and sampling time; the presence of nematodes increased the activity of JX15bacteria after21days, the nematodes increased soil IAA cntent after21days for JX15bacteria. Meanwhile, the numbers of nematodes was influenced by their species. The number of Mesorhabditis sp. was higher than Cephalobus sp..The effect of bacterial-feeding nematodes on JX15and the growth of peanut:Grazing on bacteria stimulate the growth of the bacteria; however, grazing on bacteria stimulated bacteria activity and the ability of producing IAA significantly. They were influenced by nematodes species and sampling time. The bacterial-feeding nematodes and JX15promoted the peanut growth and root development. In the five measuring indexes such as the stem length, the dry weights of peanut, the BN2treatment was much more better than another treatments; the total root length, dimension, volume and tip numbers are2to3times of B respectively; at the same time, the quantity of IAA in the earth was increased; the quantities of peanut root bacteria and actinomycete vary greatly after the BN2treatmentIn general, the strain JX15selected in this study was characterized by phosphate-solubilizing ability, high-productivity, high-activity and easy reproductive ability. In combination with the bacterial-feeding nematodes, the output of peanut and soil fertility can be efficiently improved; therefore, the strain JX15could be widely used in the fluvo-aquic soil.