(56(4):253-260)Use of Rice Blast Diseased Leaves for Preservation of Pyricularia oryzae

本研究評估以罹稻熱病之水稻病葉保存稻熱病菌之可行性。取保存於4℃下經0、2、4及5年之稻熱病罹病葉，分別測定以病葉作為接種源之有效性、罹病葉之總產孢量以及病葉上單病斑之產孢能力。結果顯示以保存達5年之病葉供做接種源時仍具致病力，保存2年之罹病葉對稻苗具強感染力與剛採集之罹病葉間差異不顯著。保存5年之罹病葉經浸水濕潤後隔日之連續2天，仍均能持續產孢，保存2年和4年罹病葉之產孢量，則與剛採集者不具顯著性差異。保存5年之罹病葉上的病斑仍具產孢能力，且保存2年和4年之病斑產孢率仍甚高，與剛採集者差異不顯著。綜合本研究試驗結果，顯示以低溫保存之罹病葉確可供作水稻稻熱病菌之接種源，經2年保存之罹病葉仍具良好之致病和產孢能力，與新鮮採集之罹病葉間無顯著性差異。The objective of this study was to evaluate the potential for using rice blast diseased leaves to preserve Pyricularia oryzae. Fresh detached blast diseased leaves and leaves stored at 4℃ for 2, 4 and 5 years were used as the inoculum sources to infect rice seedlings. They were also used to determine the amount of pathogen spores produced on diseased leaves, and the sporulated percentage of the observed lesions. The results showed that after 5-year storage the diseased leaves were still capable of initiating rice blast on rice seedlings. The diseased leaves stored for 2-year had a higher infectivity than those stored for 4 or 5 year, but had no significant difference in infectivity with those on fresh leaves. After soaking in water for 4 hours, the diseased leaves stored for 5 years sporulated continuously for 2 days. The amounts of pathogen spores produced on fresh diseased leaves and leaves stored for 2 or 4 years were not significantly different. The lesions from diseased leaves stored for 5 years were still able to sporulate. The lesions on diseased leaves stored for 2 or 4 years had higher percentage of sporulation than those stored for 5 years, and this ability to sporulate was not significantly different from those on fresh leaves. Our result showed that it is feasible to use diseased leaves stored at 4℃ for more than 2 years as the source of inoculum of P. oryzae