影響臺灣玫瑰疫病發生之生物與環境因子

Biological and environmental factors that affect disease development of rose Phytophthora blight in Taiwan

在臺灣玫瑰疫病是玫瑰受疫病菌Phytophthora nagaii或P. bishii感染所造成的，罹病植株呈現葉片黃化或失水，莖基部褐化，嚴重可造成植株死亡。P. nagaii與P. bishii在蔬菜汁瓊脂培養基上菌絲生長溫度範圍分別為8-34℃與12-34℃，最適生長溫度皆為28-32℃；將此兩種疫病菌的游走子懸浮液分別接種於盆栽玫瑰植株莖基部（“萬年紅”與“埔里之星”品種），在24-34℃皆可造成供試植株出現萎凋及死亡的病徵，而P. nagaii與P. bishii最適致病溫度分別為28-32℃與32-34℃。將前述2種疫病菌分別接種於前述2種玫瑰品種，各處理對根部浸水時間長短的病害發生情況皆相似，接種後的玫瑰盆栽根部不浸水，僅會出現輕微病徵甚至不發病，浸水4天以上會造成病害發生，浸水天數越久則病害越嚴重。分別將P. nagaii與P. bishii接種在2-6個月苗齡的“萬年紅”與“埔里之星”的莖基部，在1個月後皆會造成玫瑰發病，發病指數皆隨著苗齡之增加而降低；而接種苗齡12個月的“萬年紅”，需於接種後2.5-3個月才會開始出現病徵。田間調查結果顯示，一年生以上的“萬年紅”玫瑰在涼爽的秋季（9－10月）才開始出現病害，而非高溫多雨的夏季（6－8月），可能與成株感染後延遲發病有關。

Rose blight in Taiwan was attributed to infections from Phytophthora nagaii and P. bishii. Symptoms of infected plants included leaf yellowing, wilting, basal stem browning, and even plant death. When cultured on agar media, P. nagaii grew optimally at 28-32°C within a range of 8-34°C, while P. bishii thrived at 28-32°C, within a 12-34°C range. Artificial inoculation tests on potted rose plants (cultivars ''Wannianhong'' and ''Puli Star'') revealed that these pathogens induced wilting and death at 24-34°C. Optimal temperatures for disease development were 28-32°C for P. nagaii and 32-34°C for P. bishii. Additional tests showed that rose seedlings exhibited no or only mild symptoms without waterlogging. However, waterlogging for more than 4 days led to disease occurrence, with severity increasing with prolonged waterlogging. Inoculation of P. nagaii and P. bishii on 2-6-month-old roses (cultivars ''Wannianhong'' and ''Puli Star'') resulted in disease symptom appearance 1 month later, with severity diminishing as plant age increased. Furthermore, inoculating 12-month-old ''Wannianhong'' plants resulted in symptoms appearing after 2.5-3 months. Field survey revealed that ''Wannianhong'' roses older than a year developed the disease in cool autumn (September-October), rather than in the hot, rainy summer (June-August). This may be linked to a delayed symptom onset following infection in mature plants.