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Soybean, as a major oil crop, is one of the most widely planted crops in the world. Fusarium oxysporum causes soybean root rot, leading to great economic losses to soybean planting every year globally. Chemical fungicide for controlling soybean F. oxysporum diseases may cause environmental problems and have human health risks. Biological control methods avoid these shortcomings, however, few studies have focused on biocontrol of soybean diseases caused by F. oxysporum. Aiming at this problem, we obtained biocontrol bacteria against soybean F. oxysporum by plate confrontation method. The type of the strain with the highest biocontrol activity was identified by molecular biological methods, and then verified it biocontrol effects through greenhouse experiments. One of our isolated strain named BS06 strain had the highest activity, which was identified as Bacillus subtilis. Our study showed that BS06 strain could effectively control soybean F. oxysporum disease and significantly reduce F. oxysporum to infect soybean roots. Compared with control and carbendazim treatments, BS06 treatment had higher root biomass, plant height, leaf chlorophyll content, stem base diameter and control efficiency. Our results indicated that BS06 could effectively protect soybean root, that might BS06 strain produce substances to inhibit F. oxysporum, which was potentially useful for soybean planting.

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Background: Soil heavy metal pollution is widespread around the world. Heavy metal pollutants are easily absorbed by plants and enriched in food chain, which may harm human health, cause the loss of plant, animal and microbial diversity. Plants can generally absorb soil heavy metal pollutants. Compared with hyperaccumulation plants, non-hyperaccumulator plant communities have many advantages in the remediation of heavy metals pollution in soil. However, the amount of heavy metals absorbed could be less, and the biomass would be reduced under heavy metal pollution. The application of nitrogen (N) and phosphorus (P) is inexpensive and convenient, which can increase the resistance of plants to adversity and promote the growth of plants of heavy metal polluted soils.Methods: We designed a comparative greenhouse experiment with heavy metal contaminated soils, and set up four treatments: CK treatment (soil without fertilizer), N treatment (soil with N addition), P treatment (soil with P addition), and N+P treatment (soil with N and P addition).Results: Our results showed that plant aboveground biomass were 231.17%, 14.84%, 269.86% greater than CK treatment, respectively. N and P fertilizer stimulated plants to allocate more biomass to the aboveground parts. In addition, N treatments significantly reduced the content of Cd in aboveground and belowground biomass of plants (P < 0.05); P fertilizer significantly decreased the content of Cu in aboveground biomass (P < 0.05). N+P treatments significantly reduced the content of Cd, Cu in aboveground and belowground biomass of plants (P < 0.05). Meanwhile, N and N+P significantly increased the accumulation (mg/m2) of Cd, Cu, and Pb in plant aboveground biomass (P < 0.05). N and N+P fertilizer increased aboveground-belowground heavy metals accumulation ratio (P < 0.05), promoting plants to uptake more heavy metal pollution out of soil.Conclusions: N and P fertilizer increased the accumulation of heavy metals in aboveground of the natural plant community and accelerated the absorption of heavy metals by plants, and N fertilizer had a better effect. Our results provide an inexpensive method for remediation of heavy metal pollution in low economic value soils, such as contaminated farmland, abandoned land and mine tailings, etc.