Screening, Identification Of A Plant Growth-Promoting Rhizobacteria Of Peanut And Its Application In Red Soil

In our country, the red soil extends about1/5of the national overall earth area, due to the acid, clay, hardened and infertile characters, it was unfavorable for the microorganism growing in the red soil region, moreover, the ecological and environment system, the degradation of soil had been extremely serious there. Therefore, the red soil and its environment problem become the research hot spots of earth and environmental science in the world. This study started from the biological remediation and took sample of red soil in Jiangxi Province to grow the peanut, aimed at isolating and selecting high-efficient PGPR which suited to the acid red soil and fabricating bio-organic fertilizer for the infertile land to form the mutual-benefit system and improved the red soil environment. The study results were as follows:This study was mainly for the utilizable phosphorous release in the red soil and stimulating the plant growth; seven IAA-producing strains were isolated from peanut rhizosphere in red soil through the primary selection. Among the seven strains, the strain L-4and strain L-21had the phosphate-solubilizing ability and could secrete IAA abundantly and stably, the IAA quantities even reach135.67μ·g-ml-1and36.47μg·ml-1respectively within24hours. Because it was difficult to ensure the temperature, moisture, pH and nutrition in the soil so the bacterial strains can not survive easily. By means of Pot-promoting colonization compound screening test, it was proved that strain L-4distinctly improves the peanut growth and quantities of available phosphorus and IAA. In this case, the strain L-4can be taken as the available material for next experiment.Based on morphological, part of the physiological and biochemical characteristics and16S rDNA sequences analysis, the strain L-4was identified as Arthrobacter chlorophenolicus (GenBank Accession No. JQ277449). 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 differs from that for excretion. The optimal culturing conditions for both growth and IAA secretion were pH5-6, filling volume50ml/250ml flask, incubation at30℃for24h. The best carbon and nitrogen sources for growth were maltose and yeast extract, while xylose and KNO3for IAA production respectively. These results provided the experimental basis about the strains for the development of bio-organic fertilizer in the future.According to the percentage of20%(V/W), the fermentation medium of L-4strain was inoculated with the pig manure for4days to produce a bio-organic fertilizer (BOF) and the potted growth experiment will be implemented by using the microorganism organic fertilizer, the result proved that the secondary microorganism organic fertilizer of the strain L-4distinctly promoted the peanut growth and root development. In the five measuring indexes such as the stem length, the raw and dry weights of above-ground part, the raw and dry weights of underground part, the BOF treatment was1.5to3times of CK treatment; the total root length, dimension, volume and tip numbers are2to4times of CK respectively; at the same time, the quantity of IAA in the earth was increased as well about2.5times of that of CK; the quantities of peanut root bacteria and actinomycete vary greatly after the BOF treatment and increased about4.01and3.13times of that of CK treatment respectively as well. In contrast, the quantity of fungus decreased52.5%in comparison of CK treatment.In general,the strain L-4selected in this study was characterized by phosphate-solubilizing ability, high-productivity, high-activity and easy reproductive ability. In combination with the application of organic fertilizer, the output of peanut and soil fertility can be efficiently improved; therefore, the strain L-4could be widely used in the infertile red soil region.