Elucidation of the Characteristics of Soil Sickness Syndrome in Japanese Pear and Construction of Countermeasures Using the Rhizosphere Soil Assay Method

The continuous planting of Japanese pear leads to a soil sickness syndrome that eventually affects the growth and yield of the plant. In this study, we aimed to elucidate the characteristics of soil sickness syndrome in the Japanese pear and construct countermeasures using the rhizosphere soil assay method that can quantify the risk of soil sickness syndrome by inhibitory chemicals. Water flushing treatment, rainfall treatment, and the incorporation of test soils with different rates of activated carbon were evaluated on the risks of soil sickness. The water flushing treatment under laboratory conditions and exposure of the continuous cropping soil to rainfall in the open field decreased the inhibition rate of the soil. The decrease in soil inhibition rate was presumed to be the result of accumulated growth inhibitory substances in the soil being washed away by water. In addition, activated carbon with the potential to reduce the soil sickness syndrome was selected using the rhizosphere soil assay method. It was clarified that the mixing of the selected activated carbon with the continuous cropping soil reduced the inhibition rate and increased the growth of pear trees increased compared to the untreated soil from the continuous cropping field. The inhibition rate of the soil from the continuous cropping field was reduced to the level of soil with no history of Japanese pear cultivation. In the replanted field, these treatments can promote the growth of trees by reducing the influence of soil sickness syndrome.

Changxun Fang. Pioneers of Allelopathy: Wenxiong Lin

Wenxiong Lin did research for > 30 years in plant molecular ecology and agro-ecology, rice allelopathy and continuous monoculture problems/soil sickness of Chinese medicinal plants. His 20 Patents and most publications (about 100) have focussed on (i). Gene regulation of allelochemicals biosynthesis in allelopathic rice, (ii). allelopathic inhibitory effects on weeds, (iii). continuous monoculture problems/soil sickness in medicinal plants and (iv). the influence of allelochemicals and monoculture practice on the rhizospheric micro-environment. He helped in development of microbial fertilizer to alleviate the autotoxicity problem in continuous cropping of Radix pseudostellariae and Rehmannia glutinosa, etc. He had been the President of Asian Allelopathy Society, and got the outstanding achievement from the platform of International Allelopathy Foundation. His student, Dr. Changxun Fang got Rice Award and Grodzinsky Award respectively in the 6th and 8th World Congress of International Allelopathy Society. His elucidation of the molecular ecological mechanism of rice allelopathy was awarded the II Class Prize of Fujian Provincial Scientific and Technological Progress Award in 2007. His researches to find the mechanism of development of continuous cropping obstacle/soil sickness in R. pseudostellariae and its remedy was awarded the I Class Prize of Fujian Provincial Scientific and Technological Progress Award in 2020.

IMPLEMENTATION OF MODERN TECHNOLOGIES TO ALLEVIATE

Introduction. Urban perennial plantations are exposed to numerous anthropogenic pollutants, recreational load, etc. As a result, the physical and chemical properties of the soil deteriorate, the development of useful soil microflora is inhibited, the phytosanitary properties of soil ecosystems worsen, the intensity of mineralization processes and availability of macro- and micronutrients for plants drops down, and the concentration of toxic substances increases, which leads to soil sickness. Problem Statement. Today, in Ukraine, the causes and features of soil sickness manifestation in urban ecosystems have been virtually unexplored, and there has been no environmentally sound approach to overcoming negative consequences of this phenomenon. Purpose. To implement environmentally sound technology for overcoming soil sickness in urban green areas through the integrated use of the natural silicon containing mineral analcite and a synthetic analog of allelochemical (salicylic acid). Materials and Methods. The experimental sites have been established in the most polluted and anthropogenically disturbed green areas of the Obolon District in Kyiv. The content of micro- and macro-elements, the main ecological-trophic groups of microorganisms have been evaluated, the directions of microbiological processes have been assessed with the use of mineralization and immobilization coefficients. Plant vitality has been determined by the degree of foliar injury, crown defoliation, photosynthetic pigment content, and activity of enzymatic antioxidants in leaves. Soil allelopathic activity has been determined by the bioassay technique. Results. Physical, chemical, and biological processes related to soil-sickness in urban areas have been studied and approaches to control these processes have been determined. The innovative technology to alleviate soil sickness in urban green areas has been tested. Conclusions. The advantage of the proposed technology is a complex synecological approach that which provides optimization of agrophysical, agrochemical, and biological characteristics of soil (optimal pH level, balanced content of mineral nutrients, elimination of toxicity), enhances the adaptive potential of cultivated plants to negative biotic and abiotic factors including phytopathogens.

Allelopathic effects of ginsenoside on soil sickness, soil enzymes, soil disease index and plant growth of Ginseng

Soil sickness of ginseng (Panax ginseng C. A. Mey.) has become a major limiting factor in ginseng cultivation. We found that Total Ginsenoside in Ginseng Root (TSPG) significantly decreased the activities of soil urease, acid phosphatase and laccase. Its high concentration of TSPG (10.00 mg L-1) significantly reduced the activity of soil sucrose. Besides, the TSPG can inhibited the growth of ginseng and increased the incidence of disease. Therefore, allelopathic effects of TSPG may be one of the main causes of Soil Sickness in ginseng.

Dynamics of soil Trichoderma spp. communities in cucumber monocropping system

We monitored the dynamics of Trichoderma spp. communities in a cucumber monocropping system. Trichoderma spp. community structure and abundance were analyzed with PCR-denaturing gradient gel electrophoresis and quantitative PCR, respectively. Results showed that long-term monocropping did not affect the Trichoderma spp. community structure as indicated by the number of bands, Shannon-Wiener index and evenness index of the PCR-denaturing gradient gel electrophoresis profile. Trichoderma spp. community structure abundance was the highest in the first cropping of cucumber. Our results suggested that changes in Trichoderma spp. communities may not be the causal agent of soil sickness in cucumber monocropping.

Crop rotation alleviates replant failure in Panax notoginseng (Burkill) F. H. Chen by changing the composition but not the structure of the microbial community

Consecutive monocropping with sanqi (Panax notoginseng (Burkill) F. H. Chen) can increase the abundances of pathogens in soil, resulting in soil sickness. Crop rotation is one way to alleviate this problem. In the present study, there were no differences in microbial structure or bacterial alpha diversity among one-year monocropping soil, one-year rotation soil, and ten-year rotation soil. However, monocropping practices decreased fungal alpha diversity. The relative abundance of copiotrophic bacteria decreased after sanqi monocropping, while that of oligotrophic bacteria increased. Ten-year rotation significantly increased the abundance of potential beneficial bacterial genera. Moreover, the potential beneficial fungal genera were also enriched by rotation for ten years. Furthermore, the relative abundance of Cylindrocarpon spp. decreased dramatically after a ten-year rotation. The results of pot experiments showed that disease incidences after ten-year rotation were significantly decreased among the three treatments. Hence, we suggested that pausing sanqi cultivation for a long time can increase the abundance of potentially beneficial soil bacteria and fungi that are helpful for overcoming soil sickness in sanqi cultivation.

Long-term continuously monocropped peanut significantly changed the abundance and composition of soil bacterial communities

Soil sickness is the progressive loss of soil quality due to continuous monocropping. The bacterial populations are critical to sustaining agroecosystems, but their responses to long-term peanut monocropping have not been determined. In this study, based on a previously constructed gradient of continuous monocropped plots, we tracked the detailed feedback responses of soil bacteria to short- and long-term continuous monocropping of four different peanut varieties using high-throughput sequencing techniques. The analyses showed that soil samples from 1- and 2-year monocropped plots were grouped into one class, and samples from the 11- and 12-year plots were grouped into another. Long-term consecutive monocropping could lead to a general loss in bacterial diversity and remarkable changes in bacterial abundance and composition. At the genera level, the dominant genus Bacillus changed in average abundance from 1.49% in short-term monocropping libraries to 2.96% in the long-term libraries. The dominant species Bacillus aryabhattai and Bacillus funiculus and the relatively abundant species Bacillus luciferensis and Bacillus decolorationis all showed increased abundance with long-term monocropping. Additionally, several other taxa at the genus and species level also presented increased abundance with long-term peanut monocropping; however, several taxa showed decreased abundance. Comparing analyses of predicted bacterial community functions showed significant changes at different KEGG pathway levels with long-term peanut monocropping. Combined with our previous study, this study indicated that bacterial communities were obviously influenced by the monocropping period, but less influenced by peanut variety and growth stage. Some bacterial taxa with increased abundance have functions of promoting plant growth or degrading potential soil allelochemicals, and should be closely related with soil remediation and may have potential application to relieve peanut soil sickness. A decrease in diversity and abundance of bacterial communities, especially beneficial communities, and simplification of bacterial community function with long-term peanut monocropping could be the main cause of peanut soil sickness.