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The Improvement of Some Key Techniques for Commercialization of Disancu As A Bioherbicide

Author: LuYuXia
Tutor: QiangSheng;DaiWeiMin
School: Nanjing Agricultural College
Course: Botany
Keywords: Bioherbicide Strain QZ-2000 Digitaria sanguinalis Normal pressuresterilization Organic acid Microcapsule
CLC: S482.4
Type: Master's thesis
Year: 2013
Downloads: 3
Quote: 0
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Abstract


DISACU is a bioherbicide that was developed from conidia of the fungal plant pathogen Curvularia eragrostidis strain QZ-2000, isolated from naturally infected large crabgrass (Digitaria sanguinalis), which is virulent against large crabgrass in Weed Research Laboratory, Nanjing Agriculture University. The previous studies showed that the fungus conidia were easily mass-produced and can be safely applied to corn and soybean fields for a biocontrol of large crabgrass and other main gramineous weeds such as Chinese leptochloa, barnyard grass and so on. Hence, DISANCU has a great potential to be commercialized for a bioherbicide, which has been patented. The objectives of the study are to improve some key techniques for large production of conidia, the formula, formulation of DISANCU based on the previous studies in order to provide technique support and theoretical basis with commercialization and practical application.The cultivation and mass-production of QZ-2000conidia requires to an autoclave to create sterile conditions. If the normal pressure sterilization replaces an autoclave under high pressure to produce conidia of QZ-2000, it will cut the cost of mass-production of bioherbicide by reducing the requirements of production equipments. Different gradient treatments from25min to65min in every10min were designed to test sterilization effects. The results showed that the colony growth size and growth, sporulation, spore germination rate, spore pathogenicity of QZ-2000were promoted significantly with the prolongation of sterilization time. This effect tended to be the maximum after45min. Considering the cost and effect, the normal pressure sterilization time was determined at45min ultimately. That could be put into the practical use.DISANCU demonstrated a good weed control effect only when combining with herbicide. Organic acids could replace herbicide for a synergistic agent. In that case, it could make DISANCU to be entirely organic. The compatibility of oxalic acid and acetic acid with spores was tested. The results showed that the spore germination rate was72.86%or higher when the concentration of oxalic acid was under8750ppm. The spore germination rate was50%or higher when the concentration of acetic acid was under8000ppm. Then the mixture bioactivity with the bioherbicidal was bioassayed through the small cup and the pot plants under green house. The results showed that the stem control effect was less than80%and70%respectively when the concentration of oxalic acid was from1000ppm to4000ppm with spores. But the stem control effect was more than90%and70%respectively combining8000ppm oxalic acid with spores. When the concentration of acetic acid was from1000ppm to4000ppm with spores, the stem control effect is less than72%and70%. But the stem control effect was more than70%and60%respectively combining8000ppm acetic acid with spores. In conclusion, the appropriate concentration of organic acids could enhance the control efficacy with conidia of C. eragrostidis.After that the plot and the field experiments of organic acids combined with DISANCU were conducted in2012. The results showed that the stem control effect was less than60%and71%respectively when the concentration of oxalic acid was from1000ppm to4000ppm with spores after4weeks. But the stem control effect was more than70%and80%respectively mixing8000ppm oxalic acid with spores. When the concentration of acetic acid was from1000ppm to4000ppm with spores the stem control effect was less than60%and65%. But the stem control effect was more than65%and70%respectively mixng8000ppm acetic acid with spores. Taking into consideration of cost, effect and some other factors, the preferable control of organic acid dosage was8000ppm.The formulation of water-oil-water was not convenient and its effect was not stable in practical application. But the formulation of microcapsule using complex coacervation could overcome those problems. The experiment was conducted to develop the method of the preparation of QZ-2000microcapsule. A procedure was established in additives added-mixing-acidification-freeze-drying. The optimum menu was fixed that the water oil ratio was1:1.67, and gelatin and arabic gum concentration was2%, and lecithin concentration in oil was10%. The mixing and acidification time also influenced the microcapsule forming. Furthermore, the rate of germination, pathogenic microcapsule also showed that the furmulation was beneficial to maintain strong pathogenicity. The results showed that disease rate was more than93%when the conidia concentration was more than6×105/ml. The stem control effect was82.3%when the conidia concentration was1×106/ml in small cup experiment. In the pot experiment, the stem control effect and fresh weight effect was less than70%and85%respectively when the concentration of oxalic acid was from1000ppm to4000ppm with microcapsulated spores after4weeks. But the stem control effect and fresh weight effect was higher than80%and90%respectively when the concentration of oxalic acid was from6000ppm to8000ppm. The stem control effect and fresh weight effect was both less than60%when the concentration of acetic acid was from1000ppm to4000ppm.In summary, a suitable formulation can make the bioherbicide overcome the dependence on the humidity on a certain extent. The organic acid and bioherbicide combination can improve the bioherbicides for weed control. The formulation of microcapsule can improve control efficacy, the stability of bioherbicide, and prolong the period of the residual effect.

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CLC: > Agricultural Sciences > Plant Protection > Pesticide ( chemical control ) > Various pesticides > Herbicides ( herbicide )
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