| In the present thesis, the mechanisms of resistance to Colletotrichum gloeosporioides of red varieties of oil tea plant were systematic studied on the basis of pathological experiment, physiological measurement and analysis of disease resistance.The result showed that there were substantial differences in resistance to C. gloeosporioides among varieties of oil tea plant in natural stands. Camellia yansienensis were almost immune to C. gloeosporioides. Red varieties were resistance ones, which disease incidence were less than 1%. The Green varieties were high susceptible individuals, which mean disease incidence were over 25%, even some reached 100%. The disease incidence of mottle varieties were among the red and green varieties.In the early and late growth periods of oil tea plant, there were low latent fungi in the healthy fruits. Percentage of latent infection was about 10%, and there were no significance discrepancy among the different varieties of oil tea plants. In August when the incidence of C. gloeosporioides was at its height, latent fungi increased highly, the green varieties increased by 600%, notable highly than the red and mottle types.From May to September, the changes of acidity and buffer capacities of the peel extract filtrates of various color of oil tea plants were minor, and there were little relation between the disease resistance level and acidity and buffer capacities .The acidity changes of resistance and susceptible individuals were all around 2.74 to 3.65,which were little difference among the varieties.In May, when was the early growth period of oil tea plant, the germination rate of C. gloeosporioides were low among varieties, the tube length were about 1 to 3 u m. At the late of August when the fruit turn to weight and oil growth period, the spore germination and tube lengths were evidently increased in peel extract filtrates of varieties. Spore germination of green types reached 96.3~ 100%, which equivalent to two-fold in red types. There only 1.8% spore germinated in Camellia yansienensis extracts. Before the mature period of fruits, except for Camellia yansienensis which was 11.5%, the germination reach over 50% in other six varieties, and the difference among the red and green and also mottle types were not significant. Tube length in extracts of green varieties was higher than the red and mottle types.With the growth of oil tea plant fruits, the reducing and soluble total sugar, anthocyanidin content in peel were all increasing. The content .of reducing sugar was small negatively correlated with the disease index. Among the varieties, reducing sugar content in the pericarp of Camellia yansienensis was 5.67%, that of five-fold higher than the others, and the various of the red, green and mottle types were little. Content of soluble total sugar were significance positively related with the disease resistance, the coefficient was 0.9293,and the content of Camellia yansienensis was 18.30% higher than the other six. Mean total sugar content in resistant red ones was 22.68% higher than in susceptible green ones. Extraction method and its physical -chemical properties of the peel pigments in Yansi red varieties of oil tea plant were studied, and HCl-methanol was recommended as the best extracting agent for the pigment. The properties of the pigment extracted from peel of oil tea plant was similar to that of anthocyanidin, so the writer considered that the content which controlled the coloration of the peel of oil tea plant was anthocyanidin preliminarily. Content of anthocyanidin in peel were notable positively related with the disease resistance in natural stand, and the content in red varieties were one time much more than in green varieties and 70.7% more than in mottle ones even at the early growing period of oil tea fruit. In the middle and last period of August, when the infection of C.gloeosporioides were in top level, the positive correlation between anthocyanidin content and disease resistance were more significance.Varieties of oil tea plant fruits were... |
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