(51(4):49-56)Development of Leaf-Disk Method for Screening Melon Varieties Resistant to Sphaerotheca fuliginea Race

本研究利用接種白粉病菌於甜瓜葉片圓盤上，來快速檢測甜瓜品系對白粉病菌之抗感病性。其檢測方法如下：取苗齡3或4星期無病原菌感染之甜瓜植株上半部之新葉，經1％次氯酸鈉溶液表面消毒2～3分鐘，無菌水漂洗三次後，以打孔器取下直徑1.5公分之葉片圓盤，正面朝上，置於盛有二層滅菌瀘紙之容器中，添加適量之M-solution養液使瀘紙完全濕潤並有游離水產生，以維持葉片圓盤之活力，以吹落分生孢子方式接種每平方公分50～100個孢子濃度之白粉病菌 (Sphaerotheca fuliginea race 1)，容器加蓋密封置於24℃ / 18℃ (Day / night) 光照12小時之定溫箱中，培養10天後記錄發病指數。在室內採用葉片圓盤法測試不同甜瓜品種對白粉病之抗感病性，並對照生長箱中幼苗接種及田間植株自然感染之結果，經分析顯示其兩者之相關性高（相關係數分另 r2 = 0.9709及 r2 = 0.7924，p=0.05）。因此葉片圓盤接種法可應用於測定甜瓜品系對白粉病菌之抗感病性。A leaf-disk method was developed for disease assessment of melon powdery mildew caused by Sphaerotheca fuliginea race 1. Melon seedlings grown in growth chamber for 4 to 5 weeks were used to prepare leaf disks. The new spread leaves of melon seedling were surface-sterilized by dipping in 1% sodium hypochlorite solution for 2-3 minutes, and rinsed in sterile distilled water three times. The surface-sterilized leaves were individually cut into 15-mm diameter leaf disks with a sterile cork border. The abaxial-up leaf disks were then placed in container with 2 pieces of sterilized filter papers. Suitable volume of M-solution was added to the filter papers to maintain vitality of the leaf disks. The leaf disks were inoculated with conidia (50～100 spores/cm2) of the pathogen, and then were incubated at 24℃/18℃ (day/night) with a 12 hrs photoperiod for 10 days. For disease severity evaluation, results showed that there be a positive correlation among leaf-disk assay, seedling inoculation in growth chamber, and melon plants infected naturally in field. The relative coefficients (r2) between leaf-disks assay and seedling inoculation, and naturally infected plants were 0.9709 and 0.7924, respectively (p=0.05)