Bacillus aryabhattai MN1 作為微生物除草劑之潛力研究

Abstract

生物型除草劑的優點為兼顧環境友善、使用者安全以及消費者健康，更具有減少使用人工合成化學藥劑的優勢。本研究利用自水稻植物中篩選出之內生細菌 Bacillus aryabhattai MN1 具有可以產生高量吲哚-3-乙酸 (Indole-3-acetic Acid, IAA) 的特性，探討其於生物型除草的應用潛力。研究結果顯示 B. aryabhattai MN1 菌液上清液具有抑制雜草生長的能力，以高效液相層析儀分析以及生物鑑定法說明 B. aryabhattai MN1 所生產的上清液含有 IAA 且為影響植物之有效成分。另透過優化 B. aryabhattai MN1 的培養條件，使其能產生高量的IAA，產量最高可達 97.1 mg L-1。由萌前除草的藥效試驗中，以 IAA 基準濃度 10 mg L-1 施用量施用 MN1 上清液，即可抑制綠豆根長度的增長，並在施用 5 mL 60 mg L -1 (IAA) MN1 上清液後，阿拉伯芥和綠豆的發芽率相較於對照組分別下降了 33.3 和 60.0%；於萌後水耕除草藥效試驗中，發現施用上清液會對於阿拉伯芥並無顯著影響。而在添加展著劑之後，MN1 對於三週大小之大花咸豐草 (Bidens pilosa) 的殺草效果明顯上升，噴施 5 mL 40 mg L-1 (IAA) MN1 上清液會使葉片發生損傷、壞死、捲曲或掉落；此外，MN1上清液能選擇性地抑制大花咸豐草鮮重和乾重，對於水稻 (Oryza sativa L.) 則影響有限；而施用高濃度的 IAA MN1 上清液後，會使雜草發生細胞滲漏、葉綠素下降、丙二醛和抗壞血酸過氧化物酶濃度上升的生理現象。本研究結果顯示 B. aryabhattai MN1 具有可作為萌前和萌後雙子葉雜草生物型除草劑的潛力，達到控制田間雜草及環境友善的目的並減少化學合成藥劑的使用。

All environmental friendly, user safe, do health to consumers and synthetic chemical pesticide usage reduced are advantages of biological herbicides. In this study, we attempt to exploit endophytic bacteria Bacillus aryabhattai MN1, selected from rice plants, as a potential bio-herbicide due to its feature of high production of indole-3-acetic acid (IAA). Results indicate that supernatant produced by B. aryabhattai MN1 owns the ability to inhibit weeds growth. With high-performance liquid chromatography analysis and bioassay practice, supernatant produced by B. aryabhattai MN1 appears to contain IAA and act as active ingredients that affect plants growth. In addition, a maximum yield of 97.1 mg L-1 IAA production will be observed after optimizing the culture conditions of B. aryabhattai MN1. In the pre-emergence weeding efficacy test, MN1 supernatant is diluted based on IAA concentration as 10 mg L-1 of (IAA) MN1 treatment is capable of inhibiting green bean root length. Also, 5 mL of 60 mg L -1 (IAA) MN1 supernatant application may cause germination rates drop in Arabidopsis and green bean by 33.3 and 60.0%, in comparison to the control group, respectively. During the post-emergence hydroponic weeding efficacy test, it was found that the application of supernatant ends up no significant effect on Arabidopsis decline. However, with the spreading agent added, the effect of MN1 controlling three-weeks-old Bidens pilosa significantly increased. Spraying 5 mL of 40 mg L-1 (IAA) MN1 supernatant leads to different extent of leaf damage, necrosis, leaf curl or fall. Thus, MN1 supernatant can selectively inhibit fresh weight and dry weight of B. pilosa instead of rice (Oryza sativa L.). Besides, by applying high concentration of IAA MN1 supernatant, B. pilosa experience cell leakage, chlorophyll decline, increasing malondialdehyde and ascorbate peroxidase concentration. This study shows that B. aryabhattai MN1 possesses the potential to become a bio-herbicide on pre- and post- emergence dicotyledonous weeds control. With the development of bio-herbicide, we can achieve the goal of controlling weeds in the field and reduce the use of chemical synthetic herbicides.