利用促進植物生長細菌提升水稻生長及抵抗褐飛蝨的侵害

Abstract

促進植物生長細菌 (plant growth promoting bacteria；PGPB) 為有益植物生長的細菌，有些還能增強植物對逆境的耐受性。細菌的揮發性有機化合物 (volatile organic compounds；VOCs) 已被證實可引發植物荷爾蒙之生合成，也可能參與植物根系結構的重塑；然而，PGPB協助植物抵禦刺吸式昆蟲之機制尚未明瞭。本研究檢測具有促進植物生長潛力之細菌分離株對水稻生長和抗蟲能力的效益，試驗選用易感品種—台中在來1號 (TN1) 作為材料，發現接種分離株NO.11、NO.13和NO.16皆能提升水稻生物量累積，也發現NO.16所釋放之VOC可刺激根部IAA累積，促進幼苗根系發展；在抗蟲能力分析上，選擇水稻嚴重害蟲之一—褐飛蝨 (Nilaparvata lugens Stål) 進行測試，以褐飛蝨抗性秧苗期檢定法 (Standard Seedbox Screening Test；SSST) 發現接種NO.16的水稻能延緩蟲害，選擇試驗 (choice test) 結果顯示褐飛蝨成蟲較偏好以未接種分離株的對照組為食，推測接種NO.16會減少植株對褐飛蝨的吸引力；此外，與對照組相比，吸食接種處理組的褐飛蝨較少分泌因吸食韌皮部而產生的蜜露，也有較多未成功孵化的卵，顯示NO.16分離株具緩解水稻受褐飛蝨侵害之潛力，與改變褐飛蝨之生理表現；進一步測試葉與葉鞘抗氧化酵素活性，發現在褐飛蝨侵咬後，接種NO.16能維持水稻葉鞘中的過氧化物酶與葉片的膜穩定性，可能延緩褐飛蝨所造成的脅迫，植物荷爾蒙含量分析顯示，接種分離株能使水稻提前降低吲哚乙酸 (indole-3-acetic acid；IAA)、茉莉酸 (jasmonic acid；JA) 與茉莉酸-異亮氨酸 (jasmonoyl isoleucine；JA-Ile) 濃度，並維持水楊酸 (salicylic acid；SA) 濃度，因此推測接種分離株能使水稻提前應對褐飛蝨所造成的逆境。未來將從分子層次了解PGPB對水稻減緩褐飛蝨侵害的生理機制，探勘其對抵禦刺吸式昆蟲之調控，以提升生物農藥之應用潛力。

Plant growth promoting bacteria (PGPB) are beneficial bacteria that enhance plant growth and stress tolerance. Volatile organic compounds (VOCs) released by PGPB have potential to influence plant hormone responses and root architecture. However, the underlying mechanisms of PGPB-mediated plant tolerance to insect infection are still not clear. In this study, we tested the effects of bacterial isolates which exhibit PGP features on the growth and tolerance to brown planthopper (BPH) infestation in a susceptible rice cultivar, Taichung Native 1. The results showed that inoculation with isolate NO.11, NO.13, and NO.16 increased rice biomass. In addition, VOCs released by isolate NO.16 promoted root development, probably via the enhancement of IAA accumulation. Standard Seedbox Screening Test (SSST) was performed to evaluate the effects of isolates on rice tolerance to BPH. Inoculation of NO.16 delayed damage by BPH. In the choice test, adult BPH exhibited a preference for the mock-treated plants over the inoculated ones, indicating that the presence of NO.16 made the plants less attractive to BPH. Moreover, BPH feeding on inoculated plants secreted less honeydew derived from the phloem and had more unhatched eggs, implying the potential of NO.16 to alleviate the impacts of BPH infestation. In addition, inoculation with NO.16 maintained the membrane integrity and peroxidase activity after BPH feeding. The results of hormone analysis showed that the changes of IAA, JA, and JA-Ile accumulation in response to BPH infestation were earlier in inoculated- than mock-treated plants, suggesting that inoculation with NO.16 induced hormone responses to BPH infestation earlier in rice plants. Future research will be performed to elucidate the underlying molecular mechanisms of PGPB-mediated defense responses.