Rui Yan

The vegetation restoration project, named the Grain to Green Program, has been operating for more than ten years in the upper reaches of the Beiluo River basin, located in the Loess Plateau of China. It is significant to be able to estimate the success of preventing soil erosion. In this study, the Revised Universal Soil Loss Equation (RUSLE) and the Sediment Distributed Delivery (SEDD) model were used to assess the annual soil loss derived from water erosion. The results showed that the study area suffered from primary land use changes, with increasing grassland and forest and decreasing farmland from 1990 to 2010. Based on that, the average soil erosion modulus decreased from 18,189.72 t/(km2 a) in 1990–7408.93 t/(km2 a) in 2000 and 2857.76 t/(km2 a) in 2010. Compared with 1990, the average soil erosion modulus decreased by 59.0% and 84.3% for 2000 and 2010, respectively. Benefiting from the increased vegetation coverage and improved ecological environment, the soil erosion in this study area clearly declined. This research also found that the distribution of the three years of soil erosion was similarly based on topographic factors. The soil erosion modulus varied with different land use types and decreased in the order of residential area>farmland>grassland>forest. The average soil erosion modulus gradually increased with the increase of the slope gradient, and 76.08% of the total soil erosion was concentrated in the region with a gradient more than 15 degrees. The soil erosion modulus also varied with slope aspects in the order of sunny slope>half-sunny slope>half-shady slope>shady slope. This research provides useful reference for soil and water conservation and utilization in this area and offers a technical basis for using the RUSLE to estimate soil erosion in the Loess Plateau of China.

Diseases caused by Sclerotinia sclerotiorum have caused severe losses of many economically important crops worldwide. Due to the long term persistence of sclerotia in the soil and the production of air-borne ascospores, the synthetic fungicides play limited role to control the diseases. The application of antagonistic microorganisms can effectively reduce the number of sclerotia and eventually eradicate S. sclerotiorum from soil, therefore considerable interest has been focused on biological control. Streptomyces sp. NEAU-S7GS2 was isolated from the root of Glycine max and its rhizosphere soil. It showed significantly inhibitory activity against the mycelial growth of S. sclerotiorum with an inhitory ratio of 99.1% and completely inhibited the sclerotia germination. In the pot experiment, compared to the control, the application of NEAU-S7GS2 not only demonstrated excellent potential to control sclerotinia stem rot of soybean with 77% and 38% decrease in disease incidence and disease index, respectively, but could promote the growth of soybean. The light microscope and scanning electron microscopy showed that co-culture of NEAU-S7GS2 with S. sclerotiorum on potato dextrose agar could lead to contorted and fragmented mycelia of S. sclerotiorum, which was associated with the secretion of hydrolytic glucanse and cellulase and the production of active secondary metabolites by NEAU-S7GS2. The plant growth promoting activity of NEAU-S7GS2 was related to the solubilization of inorganic phosphate, and production of 1-aminocyclopropane-1-carboxylate (ACC) deaminase and indole acetic acid (IAA). To further explore the plant growth promoting and antifungal mechanisms, the complete genome of strain NEAU-S7GS2 was sequenced. Several genes associated with ammonia assimilation, phosphate solubilization and IAA synthesis together with genes encoding ACC deaminase, glucanase and α-amylase were identified. AntiSMASH analysis led to identification of four gene clusters responsible for the biosynthesis of siderophores including desferrioxamine B and enterobactin. Moreover, the biosynthetic gene clusters of lydicamycins, phenazines and a glycosylated polyol macrolide showing 88% gene similarity to PM100117/PM100118 were identified. These results suggested that strain NEAU-S7GS2 may be a potential biocontrol agent and biofertilizer used in agriculture.