| Replant disease was a serious problem for the sustainable production of strawberry. The expression, mechanism, and control of replant disease of strawberry were studied under different conditions such as pot trial and greenhouse trial. The results were summarized as follows:After being planted year after year in the same field, the growth and development of strawberry were depressed, development period was delayed, root diseases became serious, and yield was reduced. Diseased samples of strawberry were collected from seven plots in major strawberry-growing areas in Hebei province. Then the main pathogens causing root disease were separated from them and identified. Results showed that Fusarium oxysporum Schl.f.sp.fragariae Wiinks et Willams, Rhizoctonia solani K U hn, and Verticillium dahJiaevere the main pathogens which could infect roots solely or jointly. F. oxysporum and R. solani were more popular in Hebei province.The population of microbes in soil, rhizosphere, and root surface were affected by strawberry replanting. According to pot trial, replanting soil was beneficial for fungi. In the replanting treatment of greenhouse trial, the gross amount of fungi in rhizosphere and root surface were more than first-planting treatment. On the contrary, the gross amounts of bacterium and actinomycetes in replanting treatment were less than first-planting treatment. At the end of growing period, the proportion of bacterium to fungus in rhizosphere and root surface decreased by 57.3% and 47.5% respectively in first-planting treatment, while the numbers were 93.2% and 63.1% in replanting treatment. The proportion of anctinomycete to fungus in rhizosphere and root surface increased by 4.75 and 8.25 times respectively in first-planting treatment, while the numbers were 42.6% and 1.26 times in replanting treatment.Allelopathy of strawberry root exudation and decomposed liquid was oneof important reasons for replant disease. Allelopathy not only inhibited to the physiological activity of strawberry root system, but also promoted to growth, germination and infection of strawberry root pathogens. P -hydrobenzoic acid, pathalic acid, syringic acid, vanllic acid, frulic acid, and Benzoic acid were determined in strawberry root decomposed liquid by using HLPC, while only -hydrobenzoic acid was detected in root exudation. -hydrobenzoic acid showed the strongest inhibition effect to growth of strawberry tissue culture seedings among all of six phenolic acids.Six kinds of amino acids were determined by using ACCQ. Tag method. Arginine, proline, serine, and threonine could promote the hypha growth of F. oxysporumand R. solani. Glutamic acid, Arginine, proline, and threonine could promote spore germination of F. oxysporum and V. dahliae. Glucide was abundant in strawberry root exudation and decomposed liquid according to determination using Authrone colorimetric method. The different concentrations of glucose and sugar had different effect on strawberry root pathogens. The pathogens of strawberry root disease showed priorities to different kinds of glucide and amino acid in root exudation and decomposed liquid.Eighty-five species of medicinal plant materials were tested for the inhibition to strawberry root pathogens. Results showed that five materials had better inhibitory effects on those pathogens. After treating replanted soil by these five materials, replant disease could be controlled to some extent. Medicinal plant materials Ts-62, Ts-68 and Ts-91 were better than Ts-5 and Ts-60. Results in greenhouse trial showed that strawberry seeding in medicinal plant treatments were stronger and with lower disease index and death rate. The yield increased 32.6% ~ 33.8% compare to replanting treatment. |
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