防治馬鈴薯瘡痂病之化學藥劑及生物防治菌之應用

馬鈴薯瘡痂病主要由馬鈴薯瘡痂病菌 (Streptomyces scabies) 造成，侵染馬鈴薯表皮組織形成凸起或凹陷之木質化壞疽病斑，破壞馬鈴薯之外觀，並進而影響其經濟價值，是田間一重要病害，台灣目前尚未有推薦之化學藥劑或微生物製劑防治此病害。本實驗室先前研究發現，液化澱粉芽孢桿菌 (Bacillus amyloliquefaciens) Ba01以及馬鈴薯晚疫病之推薦藥劑：免得爛與四氯異苯腈，對於S. scabies PS07均具有抑制效果。由於單獨施用生物防治菌於田間之效率易受到環境之影響，故本研究欲結合化學藥劑與生物製劑共同防治馬鈴薯瘡痂病，期許能提升個別防治的效率，並探討藥劑對B. amyloliquefaciens Ba01重要基因表現之影響。研究首先以濾紙片擴散試驗與搖瓶培養測試出B. amyloliquefaciens Ba01對於免得爛和四氯異苯腈耐受性較S. scabies PS07高，推測可能與B. amyloliquefaciens Ba01產生內生孢子的特性有關。利用濾紙片擴散及馬鈴薯薯片試驗，發現免得爛250、125 ppm或四氯異苯腈200、100 ppm與B. amyloliquefaciens Ba01具有共同施用之潛力，且於S. scabies PS07接種1天前、後施用處理，均有好的抑制效果。而透過盆栽試驗觀察到B. amyloliquefaciens Ba01與免得爛125 ppm (罹病度為1.1 ± 1.5%)、四氯異苯腈200 ppm (罹病度為1.1 ± 1.5%) 或100 ppm (罹病度為2.9 ± 2.0%) 稀釋下混合處理相較於只接種 S.scabies PS07之正對照組罹病度較低，然在統計上沒有顯著差異。而兩藥劑並不顯著影響B. amyloliquefaciens Ba01重要二次代謝物表面素 (surfactin) 基因 srfAD以及部分參與在氮代謝相關基因 (tnrA、glnR、codY) 的表現。後續在盆栽試驗仍要調整，使S. scabies PS07有穩定之活性與毒力及族群量，並額外測試與脫氮作用相關基因的表現，以完整藥劑對於B. amyloliquefaciens Ba01氮循環相關基因的影響。研究期望能有更完整之盆栽及田間試驗進行，以期能提供農民防治馬鈴薯瘡痂病之參考。

關鍵字

馬鈴薯瘡痂病；免得爛；四氯異苯腈；液化澱粉芽孢桿菌；表面素；氮代謝

並列摘要

Potato common scab mainly caused by Streptomyces scabies leads to the symptoms of raised and pitted corky lesions on the surface of potato tubers, damaging the potato appearance and affects the economic value of potatoes. Since it is an important disease in the field, there have been no recommended chemicals or biocontrol agents to manage the disease. In the previous study of our lab, both Bacillus amyloliquefaciens Ba01 and two chemicals recommended controlling potato late blight: metiram and chlorothalonil are effective in inhibiting Streptomyces scabies PS07. Because of the unstable control efficiency of biocontrol agents in the field, the main purpose of the research is to combine chemicals with the biocontrol agent B. amyloliquefaciens Ba01 to control potato common scab and improve both control effects. Also, the influence of important gene expression in B. amyloliquefaciens Ba01 by chemicals is investigated. The disk diffusion test and shake flask assay were used at first, and the results revealed that B. amyloliquefaciens Ba01 was more tolerant to metiram and chlorothalonil than S. scabies PS07 which might be due to the presence of endospores in B. amyloliquefaciens Ba01. By adopting the disk diffusion and potato tuber slice assay, metiram 250, 125 ppm or chlorothalonil 200, 100 ppm possessed the potential in combination with B. amyloliquefaciens Ba01 which conducting 1 day before or after S. scabies PS07 inoculation retained better inhibitory effects on S. scabies PS07. By operating the pot assay, B. amyloliquefaciens Ba01 in combination with metiram 125 ppm (with disease severity 1.1 ± 1.5%), chlorothalonil 200 ppm (with disease severity 1.1 ± 1.5%) or 100 ppm (with disease severity 2.9 ± 2.0%) had lower disease severity than the positive group (with S. scabies PS07 inoculation only), while no significant difference observed. Neither metiram nor chlorothalonil significantly affected the expression of surfactin (srfAD) and partial genes involved in nitrogen metabolism (tnrA、glnR、codY) in B. amyloliquefaciens Ba01. The pot assay needs to be adjusted with stabilized activity, virulence, and population of S. scabies PS07 afterward. The expression of denitrification-related genes would be tested to complete the influence of metiram and chlorothalonil on B. amyloliquefaciens Ba01. We anticipate completing pot assay and field trial in the future and providing farmers an appropriate combination method in managing potato common scab.