Inhibition Of Plant Extracts And Their Effects On Soil Microbial Diversity In Tomato Continuous-Cropping Fields

Tomato is one of the most popular vegetables. Many production bases have been built in Guangxi, such as in Tianyang and Wuming country. However, with the long-term continuous cropping, soil-born diseases, such as tomato bacterial wilt and wilt are getting seriously in Guangxi. According to the heavy losses in yields and quality of tomato, chemical pesticides are frequently used in tomato production recently. In addition, chemical pesticides are threatening to our human beings. The growth of plant pathogens could be inhibited by plant extracts.This experiment is not only focused on the inhibitive function of plant extracts on tomato bacterial wilt and wilt, but also for their effects on soil biological property and microbial diversity. We hope that plant extacts can protect the ago-ecological environment and enhance the sustainable agriculture. The results are shown as follows:(1)The extracts, which extracted from Common Cnidium Fruit, Rhubarb, Mint and Knotweed had high inhibitive effects on the pathogens associated with tomato bacterial wilt and wilt diseases. Among them, the most effective concentrations of plant extracts were lOg/L and 15g/L. In addition, plant extracts by boiling way commonly had the better effectivity than the dipping way.(2) The numbers of culturable microorganisms, which including bacterial, fungi and actinomycetes were all decreased by the Carbendazim treatment. By contrast, soil culturable microorganisms were increased by Rhubarb treatments. And the effects of plant extracts on the numbers of culturable microorganisms were better than Carbendazim. It indicated that the effects of most plant extracts treatments on culturable microorganisms were hihger than Carbendazim, and Rhubarb was the best one.(3) The activities of β-glucosidase, phosphatase and aminopetidase were all significantly decreased by Carbendazim treatment. However, they were increased by most of plant extracts, such as Rhubarb, Mint and Knotweed. The result suggested that the effects of plant extracts on soil fertilities and health were better than Carbendazim. In addition, the most effective concentration of plant extracts was 15g/L.(4) Soil microbical biomass carbon was decreased by Carbendazim treatment. By contrast, soil microbical biomass carbon (MBC) and soil microbical biomass nitrogen (MBN) were all increased by some of the plant extracts, such as Rhubarb and Knotweed. The result also indicated that the effects of plant extracts on soil quality were better than Carbendazim. And the most effective concentration of plant extracts on MBC and MBN was 15g/L, except for Mint extract.(5) The bacterial diversity evenness and richness indices were all decreased in tomato continuous-cropping field. Though the above indices were all increased by plant extracts and Carbendazim treatments, but the effects of plant extracts were better than Carbendazim. In particularly, the most effective concentration of plant extracts was 100g/L, which was extracted from Rhubarb. In addition, sequence analysis showed that the uncultured bacterium occupied a dominant position in the soil of continuous-cropping, Carbendazim and plant extracts treatments. However, except for the uncultured bacterium, Flavobacterium sp., Chitinophagaceae bacteria、Pseudomonas sp.and Phingomonas sp. were also found in the soil with the plant extracts treatments. Among them, Pseudomonas sp. and Phingomonas sp. are considered as the benificial microbes in soil.