Effect Of Irradiation On Keeping Chestnuts Fresh And Composition Of Pathogenic Fungi Of Chestnuts

Chestnuts are very difficult for postharvest storage because it is not heat-resisting, not dry-resisting, not cold-resisting and not wet-resisting. The effect of irradiation on keeping chestnut fresh and composition of pathogenic fungi of chestnuts were investigated and results was as the following:Average healthy chestnut rates of irradiation treatments respectively were 83.6%, 85.3%,92.1%,90.3%,86.7%,85.6%,82.2% and 80.6% after that chestnuts were irradiated respectively with 0.3 kGy,0.4 kGy,0.5 kGy,0.6 kGy,0.7 kGy,0.8 kGy,0.9 kGy and 1.0 kGy irradiation dose and stored 20d at room temperature, and average healthy chestnut rate of contrast (no irradiation) was only 64.3% at the same condition. Average chestnut rot rate (Shuangji variety) of irradiation treatments was 5% after that chestnuts were irradiated with 0.5 kGy irradiation dose and stored 180d at 4℃, average chestnutrot rate (Shuangji variety) of comparison (no irradiation) was 35%. Average mouldy rate of chestnut hull was 3% after that chestnuts were irradiated with 0.5 kGy irradiation dose and stored 180d at 4℃, average mouldy rate of chestnut hull of comparison (no irradiation) was 86%. The best irradiation dose to fruits of three chestnut varieties was tested, the best irradiation dose to Shuangji variety in Longan County was 0.5 kGy and to Chushuhong variety in Longan County and Maoli in Donglan County were 0.4-0.5 kGy. After the effect of irradiation and being stored 35d at room temperature on restraining chestnut germination was observed, it showed that chestnut germination rates of irradiation with 0.1 kGy irradiation dose and comparison (no irradiation) all were 50%, chestnut germination rate of irradiation with 0.2 kGy irradiation dose was 20%, chestnut germination rates of irradiation with 0.3-0.5kGy irradiation dose all were 0. It meant that irradiation with 0.3-0.5kGy irradiation dose was effective irradiation dose on restraining chestnut germination. There were not significantly different effects of irradiation on water content of chestnut between 0.2-0.5 kGy irradiation dose treatment. Based on comprehensive effect of irradiation,0.5 kGy irradiation dose was the best irradiation dose to keeping chestnut fresh.Fourteen kinds of pathogenic fungi were isolated from chestnut fruits collected in Longan County and Donglan County of Guangxi and they were Lasiodiplodia theobromae, Botryosphaeria dothidea, Colletotrichum gloeosporioides, Fusarium proliferatum,Penicillium sp. Pestalotiopsis cocculi, Phomopsis sp., Trichothecium roseum, an unidentified fungus, Verticillum sp., Alternaria sp., Acrospeira sp., Fusicoccum sp., Cryphonectria parasitical, and the isolation rates of these 14 kinds were 76.38%,72.25%,56.38%,48.25,44.00%,38.88%,25.38%,24.75%,19.00%, 17.63%,12.25%,10.13%,8.75% and 3.87%, respectively following the sequence above, in which Lasiodiplodia theobromae and Botryosphaeria dothidea were dominant pathogens of chestnut rot in storage, Lasiodiplodia theobromae and Acrospeira sp. were first recorded as pathogens of chestnut rot in storage. Seven species of fungi including Lasiodiplodia theobromae, Colletotrichum gloeosporioides, Fusarium proliferatum, Penicillium sp. Pestalotiopsis cocculi, Phomopsis sp.and an unidentified fungus (the same as above) invaded chestnut before harvest. All 14 kinds of pathogenic fungi were isolated respectively from chestnut after irridiation with 0.2 kGy,0.3 kGy,0.4 kGy,0.5 kGy irradiation dose and contrast (no irradiation) and storage at room temperature. Seven species of pathogenic fungi were isolated from chestnuts irradiated with 0.5 kGy irradiation dose and stored at 4℃, and six species of pathogenic fungi were isolated from chestnuts of contrast (no irradiation). It meant that there was no significant difference on fungal composition between 0.2-0.5kGy doses irridiation.