| Soil microflora deterioration, peanut pathogen proliferation and soil autotoxic substances accumulation are three important factors of peanut continuous cropping obstacle. We studied the optimization mechanism of applying broad-spectrum plant endophytic fungus on peanut continuous cropping soil environment to provide more theoretical basis on inoculating endophytic fungi to alleviate peanut continuous cropping obstacle.The pot study was conducted to investigate the effect of endophytic fungi Phomopsis sp. NJ4.1, Phomopsis liquidambari B3and Ceratobasidum stevensii B6on biological characteristics of peanut continuous cropping soil. The results showed that:three treatments NJ4.1, B3and B6increased bacteria and actinomycete population; Microbial carbon (SMBC) level of treatments B3and B6were greater at seed and seeding stage, lower at flowering stage, and no significance difference at podding and maturity stage, compared to CK; NJ4.1and CK had the same trend in microbial carbon level; all treatments showed the same trend in microbial nitrogen (SMBN) level that it increased at the early growth stages, but decreased at the late growth stages; When data were averaged over the entire growth stages, NJ4.1, B3and B6had higher invertase activity and hydrogen peroxidase activity than CK, but no significance difference in urease activity. The Shannon’s diversity index from DGGE of soil bacteria and fungi were both highest in B3treatment at flowering stage. Three treatments NJ4.1, B3and B6improved peanut yield, plant height, stalk weight and number of branches, and B3had the highest yield, increasing12.4%compared to that of CK.In view of the B3treatment had the best optimization effect, we select B3to further study its effect on dynamic changes of peanut soil-borne pathogen Ralstonia solanacearum and Fusarium spp. population. We also developed a real-time polymerase chain reaction(PCR) assay to detect and quantify Phomopsis liquidambari B3. B3treatment had no obvious inhabiton effect on two pathogens. In comparison with CK, the population of Ralstonia solanacearum in the treatment with B3inoculations was higher during the4weeks after inoculation, but was no significance in the later several weeks in the pot experiment. The treatment B3did not reduce the population of Fusarium spp. significantly compared to CK. Amplification of Phomopsis liquidambari B3DNA using Bf1/Br1primer pair yielded a single PCR product320bp long, and this primer pair did not amplify the320bp band from any of the other9species. When Phomopsis liquidambari B3was inoculated into soil, the content of genomic DNA reached to the highest4.2log (pg/g dry soil) immediately, but it decreased below the detection limit after4weeks.B3was also selected to study its effects on the degradation of peanut potential autotoxic substance flavone luteolin. When concentration of luteolin reached to10mg·L-1, it significantly reduced peanut seed germination index, peanut seedling root length and fresh weight. In liquid culture,98.1%luteolin was removed at B3treatmented group, lower than the minimum inhibitory concentration to the peanut. In soil condition, luteolin removal rate got98.7%(<peanut minimum inhibitory concentration), and it only reached78.8%in that of CK.In conclusion, the broad-spectrum plant endophytic fungi had obvious improvement effects on yield reduction and plant growth restriction of peanut caused by continuous cropping. We consider that the optimization mechanism of applying endophytic fungi to alleviate continuous cropping soil environment is mainly on soil microbial flora balance as well as on soil peanut autotoxic substance degradation.
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