鏈黴菌Streptomyces plicatus對Phytophthora capsici引起青椒冠腐病之生物防治效用探討

Evaluating the biocontrol efficacy of Streptomyces plicatus on Phytophthora crown rot of pepper caused by Phytophthora capsici

疫病菌Phytophthora capsici對台灣和全球的蔬果生產都構成重大威脅。放線菌Streptomyces plicatus strain B4-7為具有抑制疫病菌的生物防治微生物，將B4-7燕麥培養液經過C18固相萃取管分離不同極性的濾液，並與P. capsici isolate 28089進行拮抗試驗。拮抗試驗數據顯示，極性較低的SPE濾液對疫病菌絲生長具有強烈的抑制作用，並造成疫病菌絲與孢囊的型態變異。為了讓B4-7能運用到作物病害綜合防治策略中，我們透過圓盤濾紙試驗，評估五種疫病常用的殺菌劑對B4-7菌落生長影響。結果顯示，除了四氯異苯腈和氫氧化銅之外，達滅芬、依得利和滅達樂皆對B4-7的生長不具有抑制作用。進一步將B4-7燕麥培養液與殺菌劑分別、或混合施用於盆缽試驗，觀察對青椒冠腐病的防治效果。實驗數據顯示，單獨施用B4-7發酵液時，對青椒冠腐病的抑制率為100%。在單獨施用氫氧化銅，或依得利的處理組亦是100%的抑制率。在B4-7+依得利混合處理組（皆濃度減半）的疾病嚴重度為0%，感染率0%，與對照組（93.8%、100%）有顯著抑制病害發展。在B4-7+氫氧化銅（皆濃度減半）處理組的疾病嚴重度則為12.5%，感染率12.5%，同樣具有顯著抑制效果。綜合上述結果，本研究所評估之S. plicatus B4-7具有非農藥防治青椒疫病、降低作物損失、降低用藥劑量的潛力，可作為青椒疫病管理策略的選項之一。

Phytophthora capsici is a significant threat to vegetable production in Taiwan and globally. Streptomyces plicatus strain B4-7 has emerged as a promising biocontrol agent against Phytophthora blight. Analysis using C18 solid-phase extraction (SPE) fractions of B4-7 in anti-fungal assays against P. capsici demonstrated that lower polarity SPE fractions exhibited robust inhibition of mycelial growth and induced abnormal sporangium formation. To use the biological agent B4-7 together with fungicides in crop disease control, we tested the inhibitory effect of five recommended fungicides on B4-7's mycelium growth through paper disc assays. The results showed that, except for chlorothalonil and copper hydroxide, dimethomorph, etriazole, and metalaxyl, exhibited no inhibitory effects on B4-7. When the B4-7 culture broth was applied to Phytophthora-infested peppers, it resulted in 100% inhibition. Similarly, applying copper hydroxide or etriazole alone to the infested plants yielded the same results. Co-application of halfdosages of B4-7 culture broth and copper hydroxide, or etridiazole, significantly reduced the disease severities (12.5%, 0%) and infection rates (12.5%, 0%) of Phytophthora crown rot disease compared to the control treatments (93.8% and 100%) in peppers. These results suggest the potential of combining S. plicatus B4-7 with fungicides in an integrated approach for Phytophthora blight management.