| Summary: | 碩士 === 國立中興大學 === 土壤環境科學系 === 88 === Nitrogen form is one of the important factors that affect the occurrence of diseases, its management depend on crop and pathogen. Oxalic acid has been applied to induce crop resistance, but always appear necrosis in crop leaves, and decrease the economical value of flowers. There is no research about the effect of citric acid and malic acid on crop resistance. Three experiments of this thesis were designed to study the effect of nitrogen form on the occurrence of gray mold on gloxinia, and the effect of different concentrations of oxalic acid, citric acid and malic acid on the control of gray mold on gloxinia.
Sand medium was used to study the effect of various NH4+-N/NO3--N ratios in the nutrient solution on the growth of gloxinia. Results show that when the content of ammonium nitrogen increased the dry weight, the pH value of media, and the content of potassium, calcium, and magnesium in plant were increased. When treated with nitrate nitrogen as sole nitrogen source, the microelements in shoot were decreased. When the content of ammonium nitrogen in the nutrient solution was decreased, the foliar disease severity was increased relatively. And the optimum content of ammonium nitrogen was 23-32%. The flower disease severity had significantly different between the treatment at 3rd day after inoculation, but up to 100% at 6th day.
The foliar spraying of different concentrations of citric acid, oxalic acid and malic acid to study the effect on gray mold. Results show the treatment of organic acids sprayed when on leaves didn’t decrease dry weight, but affect the nutrient content in shoot and tuber. The foliar disease severity of oxalic acid in 35 mM was significantly higher than other treatments in each surveyed date, as a result of foliar injury. The citric acid and oxalic acid in 5 mM and malic acid in 20 mM induce low disease severity.
Liquid medium supplied with different concentrations of organic acids to study the effect on mycelial growth of Botrytis cinerea. The citric acid in both 5 mM and 20 mM of citric acid could enhance mycelial growth of T-3393a isolate of Botrytis cinerea. However, the other treatment has similar trend that when the concentration of organic acids increased the mycelial dry weight decreased, the results indicate that high concentration of organic acids inhibit mycelial growth of Botrytis cinerea.
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