利用真菌防治尖瓣花（Sphenoclea zeylanica）之探討

Host specific Alternaria.- a potential biocontrol agent for gooseweed (Sphenoclea zeylanica Gaertn.)

尖瓣花（Sphenoclea zeylanica Gaertn.）是台灣稻田中常見之闊葉雜草，近年來在部分地區，尖瓣花族群明顯增多，已成為稻田中優勢雜草，嚴重影響稻作生產。本研由台中縣霧峰地區，自然罹病尖瓣花分離得到真菌Alternaria sp.，進行生物防治應用潛力研究。在實驗室及溫室完成病原菌培養及病原性測定，Alternaria sp. SPHZE 60菌株，在25-30℃之溫度條件下生長最快速；以1×10^3、1×10^4、1×10^5 spores/ml，噴施於溫室盆栽種植之尖瓣花植株，1×10^5 spores/ml的處理組呈現高度的發病病徵，尖瓣花株高受抑制達80.1%、生物量減少89.7%。另外將此菌接種於CDA、CMA、FCA、FGA、MPA、OMA、PDA、HPA、SCA及V8A等人工培養基，在25℃、持續日光燈照射下培養15天，以SCA及V8A兩種培養基的產孢量最高，每個培養皿可產生2.9-4.5×10^6個分生孢子。SPHZE 60菌株對寄主具高度之選擇性，只感染尖瓣花，對其他受測試之17科25種植物則無病原性。在溫室中將尖瓣花與水稻栽種於同一個植盆內，再接種SPHZE 60（2×10^5 spores/ml）；接種後，尖瓣花之生長受到抑制，嚴重者可在接種後第三週死亡；SPHZE 60對尖瓣花株高之抑制效果，從第一週36.7%到第四週77.4%，最後達第八週88.9%。接種後12週，收割水稻進行產量影響調查，接種病原菌之處理組，稻株平均重179.0g、榖粒平均重35.5g，而未接種病原菌之對照組稻株平均重68.0g、榖粒平均重8.8g；相較於僅種植水稻而沒有尖瓣花之正常水稻對照組，接種病原菌組之產量與其無顯著差異。測試之結果顯示，此對尖瓣花有強致病性之Alternaria真菌，具有進一步開為發生物除草劑之潛力。

"Gooseweed (Sphenoclea zeylanica Gaertn.) is a common, annual herbaceous weed of paddy rice (Oryza sativa L.) fields in Taiwan, and it has gradually become a dominant weed in recent years. To develop a non-chemical strategy for the control of gooseweed, research was conducted to look for suitable fungi to control the weed. Diseased tissues of gooseweed were collected from local paddy fields, and pathogenic microbes were isolated from them. Pathogenicity of the fungal isolate SPHZE60 to gooseweed was confirmed. Inoculum at a strength of 1 × 10^5 spores/ml provided effective control of gooseweed with an 80.1% decrease in its height and an 89.7% decrease in its biomass. Ten different artificial media were tested for the sporulation of SPHZE60. Results of the study showed that SCA and V8A media produced the most conidia at (2.9 - 4.5) × 10^6 spores/dish. The host range of SPHZE60 was determined by inoculating 1 × 10^6 spores/ml onto 25 plant species in 17 families. No plant species showed symptoms except for gooseweed. Greenhouse studies were conducted to compare the pathogenicity of SPHZE60 to potted rice and gooseweed plants. Pots inoculated with a spore suspension at 2 × 10^5 spores/ml were compared weekly with those without inoculum. The height of the gooseweed dramatically differed between treated and untreated pots. Those inoculated with SPHZE60 showed 88.9% inhibition in height in the eighth week after inoculation. The height of rice in the 2 treatments exhibited no significant difference, but the tiller number was apparently lower in the control. Rice was harvested at 12 wk after inoculation to determine its biomass and yield. Rice treated with SPHZE60 grew normally and produced regular yields. The SPHZE60 fungal isolate was proven to be a potentially promising biological control agent for gooseweed."