| Apple anthracnose caused by Colletotrichum gloeosporioides has been an important disease of postharvest apple, which caused fruit tot during storage. In this paper, research on the pathogenesis and the resistance of apple varieties to Colletotrichum gloeosporioides on the basis of physiology and biochemistry were studied. Also the effects of physical, chemical and biological factors to control this disease were studied. The experimental results were summarized as follows: 1. Identification of the Resistance of Apple Varieties to Apple Anthracnose Caused by Colletotrichum gloeosporioides Resistance of five apple varities to Colletotrichum gloeosporioides were identified by means of disease index. The results through Duncan's multiple range test showed that the difference of the resistance of varieties were significant(P=0.01). Hongfushi was susceptible. Gala and Qiaonajin were mid-susceptible. Liaofu was mid-resistant. Huangjinshuai was resistant. 2. Study on the Pathogenesis of Colletotrichum gloeosporioides Activities of the cell wall degrading enzymes (CWDEs) produced by Colletotrichum gloeosporioides both in vitro and in vivo were studied. The results primarily demonstrated that PMG and Cx played pathogenic roles during the infection. In vitro, PMG activity showed an increase trend during culture days, and Cx activity increased then decreased, while PMG activity was always higher than Cx acticity. In vivo, the peak of PMG activity appeared formerly and the peak of Cx activity appeared later whether in resistant variety or in susceptible ones after inoculation. The enzyme activities of CWDEs in resistant variety were lower than those in mid-susceptible one and in susceptible one, but the peak in resistant variety showed earlier. In addition, CWDEs could also be detected in healthy apple fruits without inoculation, however the activities were lower. 3. Effects of the Extraction Juice from Apple Fruits to the Spore Germinating Percentage of Colletotrichum gloeosporioides The spore of Colletotrichum gloeosporioides were cultured in extraction juice from different apple fruits. The results showed that the germinating percentages of spore were high in susceptible varieties, which were close to the ones in CK. While the germinating percentages of spore were low in resistant varieties, which were below 50 percentage. In different periods after inoculation, the germinating percentages of spore were varied. 4. Study on the Resistance Mechanism of Different Apple Varieties to Colletotrichum gloeosporioides 4.1 Fungi Cell Wall Degrading Enzymes The activities of β-1,3-glucanase and Chitinase in apple fruits were both induced after inoculating Colletotrichum gloeosporioides, and the activities of Chitinase were increased in larger scope than those of β-1,3-glucanase. The activities in susceptible varieties were a little higher than those in resistant one, but the difference was not apparent. The activities in susceptible varieties always maintained increased during all time of infection, while the activities in resistant variety dropped gradually in later period of infection. There was no obvious change in activities in apple fruits of CK. 4.2 Major Defence Enzymes of Host By means of mensuration the enzyme activity, postharvest fruits of three apple varieties with different resistance to apple anthracnose were inoculated with Colletotrichum gloeosporioides, the changes of activities of peroxidase (POD) ,polyphenoloxidase (PPO) and phenylalanine ammonia-lyase (PAL) were studied. Results showed that the activities of POD in different varieties were all induced after inoculation, and were higher than those of CK, but the activities in resistant variety increased in a large scope, the maximum appeared early and maintained on the high level; the activities in mid-susceptible and susceptible varieties increased slowly, the maximum appeared late, then decreased rapidly. We also found that the activities on the infected spot (1cm) were highest, the activities on the infected spot were obviously higher than that... |
PDF Full Text Request