| Summary: | 博士 === 國立臺灣大學 === 園藝學研究所 === 101 === Of all the problems in the mango industry, anthracnose is the most difficult one to solve. To improve mango anthracnose management in Taiwan, it is an important issue to understand the critical timing when anthracnose pathogen invades mango panicles. Also, the anthracnose pathogenesis affected by ethylene may be a clue to solve this problem. In this study, panicles and fruitlets of ‘Irwin’ mango were inoculated with conidial suspensions at different developmental stages and treated with ethylene or the reaction inhibitor, 1-MCP.
The concentration of anthracnose conidial suspension used in the experiment was 105 conidia/mL and fruitlets whether detached from trees or not were always infected. Fruits in 100% RH for more than 10 minutes, with wounds or latex contamination on the peel all favored the infection of anthracnose.
Invaded panicles at the full blooming stage resulted in 67.2 % of panicles without setting any fruit and 61.1 % of the fruitlets dropped in the remaining. The highest latent infection rate in the unripe fruits while the highest infection rate and largest infected area presented in the ripe fruits during the postharvest stage. The results were indicated that full blooming stage was the critical stage for C. gloeosporioides management, and suggest that controlling the pathogens population of field before full blooming stage should be emphasized in routine practice.
Fruitlets at different developmental stage inoculated by conidial suspensions, the infection was promoted by ethylene treatment but inhibited by 1-MCP treatment. The observation of mango tissue slices indicated that ethylene but not 1-MCP induces the attachment of anthracnose spores and the formation of appressoria and penetration peg. Ethylene was suggested to be the inducement in anthracnose pathogenesis and the infection would be ceased by 1-MCP. Fruits inoculated at fruitlet stage, harvested at later different developmental stages and treated with ethylene had higher infection rate, larger infected area and faster ripening rate, and the fruits treated with 1-MCP had lower infection rate but similar infected area to ethylene treatment. Lesions began to develop on the fruits harvested at fruitlet stage was prior to fruits ripening but developed later than ripening on the fruits harvested at mature stage. No significant difference was observed on the respiration rate of mango fruits treated or untreated with ethylene,1-MCP after inoculation, neither after fruit ripening. The results showed ethylene did play an important role in latent infection, but some phenomena such as ingredients changes, flesh softening and respiration rate rising, the character of mango fruits physiology induced by ethylene, shall be involved. Since the more fruits ripened, the more infection symptom developed on the mango fruits’s peel. The following conclusion can be drawn from this study that ethylene promote the mango anthracnose infect directly, and then induces the fruit ripen that made anthracnose infected more easily. Another experiment was undertaken on mature Irwin mango by both 1-MCP and hotwater treatment in simulated shipping condition, and it was not effective to free from the threat of anthracnose.
Due to the complex reaction in Irwin mango to defend the invasion of anthracnose, it is suggested that the better timing to control the disease is on preharvest stage, especially before full blooming stage, rather than on postharvest stage.
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