(13(4):28-35)STUDIES ON DAMPING-OFF DISEASE OF FIBER CROPS I. Ecological Studies on Pellicularia filamentosa (Pat.) Rogers Causing Damping-off of Fiber Crops (2)

1. 本研究之目的為探求P. filamentossa在黃麻引起子苗立枯型腰折病所需之土壤溫度，濕度。並於土壤內增用植物添加物及不同氮素源，觀測是否可抑制病害之發生。 2. 黃麻幼苗在土壤溫度10~35℃均可發生腰折病，23~27℃最適宜於發病，而以25℃發病最激烈。 3. 土壤濕度以10~45%含水量均可使黃麻幼苗發生腰折病。在此範圍內，含水量愈少發病愈烈、20%含水量發病最多。土壤過濕或過份乾燥，則可使麻株生理異常增加死亡。 4. 土壤中加入植物有機質可使黃麻種子減少P. filamentosa侵害，其結果尤以太陽麻稈添加物時最顯著。兩種不同氮素源，NH4NO3及Uramite各以l00ppm加入各添加物處理內，可明顯減少種子被感染及幼苗死亡，罹病程度等。若僅二種化學氮素源相比較，則速效性NH4NO3顯然比遲效性 Uramite更見效。 5. P. filamentosa菌株對黃麻精洗麻纖維素破壞能力互不相同，菌株 K2 , T 及 B2 等3菌株對纖維素破壞能力最強，次為 K3 , J , B1，及R等4菌株。菌株U則完全不具破壞能力。 1. The purpose of this study is to determine the soil temperature and moisture which are favorable to Pellicularia filamentosa causing seedling damping-off of jute. Five Kinds of mature plant materials and 2 forms of supplemental nitrogen were added in the sick soil to test the effect in reducing the disease. 2. Jute seedlings infected by P. filamentosa were found at the range of soil temperatures from 10 to 35°C. The optimum soil temperature was at 23-25-27°C. 3. Damping-off of jute seedlings generally occurred at 10-45% soil moisture, the disease becomes more severe when soil moisture was maintained at low level, parti-cularly at 20%. However, jute seedlings become dead when soil moisture was higher than 45% or lower than 10%. 4. All kinds of plant materials added in the soil were effective to prevent seed rot and pre-emergence rot, especially with the addition of crotalaria in sick soil. soluble NH4NO3 and the slowly available Uramite were also offective in reducing disease severity when they were added to provide 100 ppm of in each treatient. 5. Each isolate of P. filameitosa showed different degree of destructiveness on fiber cellulose of retted fiber of jute. Among the 12 isolates, K2, T and B2 were found to be most destructive, K3, J, B1 and R the next, and the ioslate U no harm to fiber cellulose was observed