藉由Bacillus amyloliquefaciens啟動西瓜內源之免疫反應於果 斑病之防治

Bacillus amyloliquefaciens primes PAMP-triggered immunity to control bacterial fruit blotch of watermelon

張俊傑(Jun Jie Chang)

指導教授 ： 林宜賢

國立屏東科技大學/農學院/植物醫學系所/碩士(2016年)

摘要

由Acidovorax citrulli所引起之西瓜細菌性果斑病，為西瓜生產之重要限制因子。此病害主要以帶菌之種子為主要初次感染源，於種子發芽時入侵子葉，再藉雨水或噴灌使病原菌散播至鄰近之植株。隨病害之發展使果實造成大面積汙斑，嚴重影響商品價值。因此，解決種子帶菌之問題為防治細菌性果斑病發生之重要策略。目前解決種子帶菌問題大多以化學藥劑處理為主，而化學藥劑處理並無法有效解決種子帶菌問題，發展微生物於此病害之防治或許為可考量的方向。本篇報告中，首先篩選由土壤分離之Bacillus spp.菌株，結果顯示Bacillus spp. PMB04、PMB05與DR81三個菌株對 Acidovorax citrulli具拮抗能力，其中DR81具有最強之拮抗能力。接著利用16S rDNA 進行菌株定序與比對，結果顯示PMB04與PMB05菌株為B. amyloliquefaciens，DR81則為B. thuringiensis。進一步評估具拮抗特性之PMB04、PMB05與DR81菌株在防治細菌性果斑病之能力，分別進行葉片接種與種子處理。在葉片的接種上，相較於對照組僅PMB04與PMB05可明顯抑制病害之發生。在種子的處理中，亦僅有PMB04與PMB05可有效降低幼苗之罹病率，且以PMB05之防治效果最佳，防治率達96.6 %。由前述之結果推測，拮抗作用非為防治西瓜果斑病之唯一因子。因此，進一步分析在拮抗菌與病原菌共同存在下之H2O2快速產生、癒傷葡聚糖累積及防禦相關酵素活性變化來探討此些拮抗菌株是否具有強化植物免疫能力。結果顯示PMB04與PMB05均能增加果斑病菌於葉片中所誘導之H2O2與callose累積，及提升多酚氧化酶活性，其中又以PMB05較為顯著。說明此二菌株可強化植物免疫之防禦訊號與誘導抗病性來降低果斑病之發生。綜合上述，PMB04與PMB05在防治細菌性果斑病上具有優異之效果，且其防治機制可能與拮抗微生物所提升之植物免疫有關。

關鍵字

細菌性果斑病菌 ； 生物防治 ； Bacillus屬 ； 植物免疫

並列摘要

Bacterial fruit blotch (BFB) caused by Acidovorax citrulli is an important limiting factor on watermelon production. Since the infested seeds can be the primary inoculum to cuase epidemics in field, reducing the development of pathogen on seedlings becomes a possible strategy to control BFB. To explore a environmental friendly strategy, the application of plant growth promoting rhizobacteria (PGPR) is available. In this study, Bacillus spp. isolated from soil were screened based on the antagonistic activity firstly. Three antagonistic strains, PMB04, PMB05 and DR81 were selected and identified by the sequences of 16S rDNA. Results exhibited that PMB04 and PMB05 were identified as B. amyloliquefaciens, and DR81 was identified as B. thuringiensis. These antagonistic strains were further applied on A. citrulli-infested seeds, and the disease incidence and disease severity were significant reduced. Among them, weak antagonistic PMB04 and PMB05 exhibited strong control efficacy against BFB of watermelon rather than strong antagonistic strain, DR81. Moreover, leaf infiltration revealed the symptoms and populations of BFB were strong reduced by PMB04 and PMB05. To realize the interaction between antagonistic strains and innate immunity of watermelon, signals of PAMP-triggered immunity intensified by antagonistic strains were assayed. Results revealed that the rapid ROS generation and callose deposition were significant intensified by PMB04 and PMB05 upon the inoculation of A. citrulli, especially PMB05. In addition, growth of watermelon seedlings were significant improved by PMB04 and PMB05. Therefore, we concluded that plant immunity primed by plant growth promoting rhizobacteria, such as PMB05, was a novel efficient strategy to control BFB of watermelon.

並列關鍵字

Acidovorax citrulli ； biocontrol ； Bacillus spp. ； plant immunity

參考文獻

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