(13(2):46-54)STUDIES ON DAMPING-OFF DISEASE OF FIBRE CROPS I. Ecological Studies on Pellicuaria filamentosa (Pat.) Rogers Causing Damping-off of Fibre Crops

一、Pellicularia filamentosa之8菌株分離自一般纖維作物，6菌株分離自其他作物，其寄主範圍均相一致，惟因菌株之不同對各類作物可呈現強弱不一之病原性。 二、分離自纖維作物病株之Pellicularia filameutose 8 菌株以側定棉及黃麻不同生育狀況之感病程度差異性，結果於不同菌株間，病原性可發生差別之事實，固不待言，然棉與黃麻因生育狀態不同而感染之易否亦可發生差異。棉以苗齡愈小，罹病愈容易。黃麻則以發芽後5~15日之間罹病指數最高，過此時期，雖亦可發病，但其程度急劇降低。 三、分離自纖維作物病株之Pellicularia filameutosa 8 菌株用以測定菌絲之癒合現象（Fu-sion of hyphae）結果，各菌株之菌絲癒合之程度不盡一致。其中以菌株 K l 與 C , T 與 F K3與 K 2與 T , K 3 與 U , C 與 T , U 與 F 及 T 與 F 均可進行完全癒合現象。 四、供試Pellicularia filamentosa各菌株對纖維素之破壞能力，因不同菌株而發生差異。菌株 K 2 破壞能力最強，次為菌株 T , U P，最弱都為菌株F，僅可發生極輕微破壞現象。 1. Among 14 isolates of Pellicitlaria filamcntosa, 8 isolates were isolated from the fibre crops and 6 from other plants. They had the same host range, but the pathogenicities of these isolates were quite different on various crops. 2. 8 isolates of Pellicularia filamentosa isolated from fibre crops were inoculated to different growth stages of cotton and jute, they showed different pathogeni-cites from one another. On cotton, small seedlings stage easily infected. On jute plants, high disease index was found on seedings 5 to 15 days after germination, and degree of infection was greatly reduced after this period. 3. The degrees of fusion of hyphae were different among 8 isolates obtained from the disease plant of fibre crops. However, isolates K1 and C, T and F, K2 and K3, K2 and T, K3 and U, C and T, U and F could Progress perfect fusion with each other. 4. Each isolate of Pellicularia filamntosa showed different destructive power to fiber cellulose, isolate K2 was the strongest one, isolate T, U and P the next, F and R were the weakest, the other were lower than 20% as shown in table 6