|Title:||鶯歌桃果實疫病||Other Titles:||Phytophthora fruit rot of peach in Taiwan||Authors:||安寶貞
|Keywords:||桃;果實疫病;Phytophthora meadii;P. citrophthora;Peach;Phytophthora fruit rot;Phytophthora meadii;P. citrophthora||Issue Date:||Sep-2003||Publisher:||中華民國植物病理學會||Journal Volume:||12||Journal Issue:||3||Start page/Pages:||181-190||Source:||植物病理學會刊||Abstract:||
一九九九年六月至七月間台中石岡一鶯歌桃果園的果實採收後，於儲運期問發生嚴重腐敗現象。罹病果實初現淡褐色水浸狀圓形斑點，病斑面積迅速擴大轉為暗褐色，並長出白色密緻的黴狀物。經組織分離，共獲得兩種疫病菌，分別為Phytophthora meadii與P. citrophthora，將兩種疫病菌的游走子接種於鶯歌桃果實，2-3天後均會造成果實腐敗，病徵與儲運期間發生者一致，證明此種桃果實腐敗係由疫病菌引起。此外，自罹病果園與鄰近碰柑園內的落果、根系與土壤中，均可以分離至到P. citrophthora。由於農民於果實採收後曾以水清洗所有果實，而果實於2-3天內嚴重發病，因此推測桃果實發病原因，為少數罹病果實上的胞囊於清洗過程中釋放人量游走子成為二次感染源，再侵染其他健康果實所致。採收時如將病果剔除，並在清洗水中加人10 ppm次氯酸鈉，可有效防治該病害。兩種疫病菌有部份特性相似，包括菌絲生長溫度為8-32℃，最適溫為20-28℃；胞囊具顯著乳突及脫落性，胞囊柄長中等，平均約為9 11 m，均不形成厚膜胞子。兩者的相異處為P. meadii的胞囊較長，長寬比值平均約為1.5-1.6，而P. citrophthora者較短，約為1.3；其中P. meadii均為A2配對型，本身會形成卵胞子(self-oospores)；而P. citrophthora為A1配對型，但本身不會形成卵胞子。當兩者直接配對時亦無卵胞子產生。此外，兩菌的菌絲蛋白質電泳圖譜相近，僅有些微差異。在台灣，疫病菌危害鶯歌桃果實為首度報導，而P. meadii危害桃樹為世界首度發現。
Peach (Prunus persica) fruit, harvested from an orchard located at Shigang, Taichung County, occurred a serious disease in 1999. Light brown water-soaking spots appeared on affected fruit at the early stage. The diseased areas turned brown and soft, and were covered with a thick layer of white mold subsequently under high moist condition. Phytophthora meadii and P. citrophthora were isolated from diseased fruit. Disease symptoms similar to those appeared in the field and market were reproduced on the fruit 2-3 days after inoculation with zoospore suspension of each Phytophthora isolate tested. The same fungi were reisolated from all of the inoculated diseased fruit. Since all harvested fruit were washed with the water collected from a ditch nearby and most disease symptoms appeared within 2-3 days in the market, the severe Phytophthora fruit rot of peach might be a result of zoospore infection during the washing process. P. citrophthora was frequently isolated from the fibrous roots and rhizosphere soil of peach plants as well as the dropped citrus fruits, roots and soil in an adjacent ponkan orchard. It was considered possible that the diseased fruit from the field produced large amount of zoospores in the wash water, severing as secondary inoculum to infect other health fruit. Removing diseased fruits combined with adding 10 ppm NaClO into the washing water was highly effective in controlling the Phytophthora brown rot disease. Some characteristics of the two Phytophthora species from peach were similar. Both species were able to grow on V-8 agar between 8-32 with the optimum growth temperature of 20-28 . Sporangia of both species had semi-spherical papilla and were deciduous with pedicel length about 9-11 m in average. Chlamydospores were absent. However, the colony patterns of the two species grown on V-8 agar and PDA were different. Sporangia of P. meadii isolates (L/B ratio of 1.5-1.6) were much longer than those of P. citrophthora isolates with L/B ratio of 1.3. All of the peach isolates of P. meadii belonged to A2 mating type, which formed self-oospores while paired with A1 type of P. parasitica and vice versa. All P. citrophthora isolates were A1 type, which stimulated A2 type of P. parasitica to form oospores but didn't form self-oospores themselves. Sex organs were not produced when these two species were paired directly. The mycelial soluble protein patterns of isolates of both species analyzed by SDS PAGE electrophoresis were similar but with some difference. This is the first report of peach Phytophthora fruit rot in Taiwan. To our best knowledge, this is also the first report of peach fruit disease caused by P. meadii in the world.
|Appears in Collections:||植物病理組|
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