Gattoni Kaitlin M, Park Sang Wook, Lawrence Kathy S
Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, United States.
Front Plant Sci. 2023 Jan 20;13:1079109. doi: 10.3389/fpls.2022.1079109. eCollection 2022.
The goal of this research is to determine the mechanism of action of two spp. that can manage population density in cotton. The overall objectives are 1) determine the efficacy and direct antagonistic capabilities of the spp. and 2) determine the systemic capabilities of the spp. The greenhouse assay indicated QST713 and I-1582 could manage similarly to the chemical standard fluopyram. An assay determined that I-1582 and its extracted metabolites were able to directly manage second stage juveniles by increasing mortality rate above 75%. A split root assay, used to determine systemic capabilities of the bacteria, indicated QST713 and I-1582 could indirectly decrease the nematode population density. Another species, strain 2, also demonstrated systemic capabilities but was not a successful biological control agent because it supported a high population density in greenhouse assay and in the split root assay. A RT-qPCR assay was used to confirm any systemic activity observed in the split root assay. At 24 hours both QST713 and I-1582 upregulated one gene involved in the initial stages of JA synthesis pathway but not another gene involved in the later stages of JA synthesis. These results point to a JA intermediate molecule, most likely OPDA, stimulated by the bacteria rather than JA in a short-term systemic response. After 1 week, the spp. stimulated a SA-responsive defense related gene. The long-term systemic response to the spp. indicates salicylic acid also plays a role in defense conferred by these bacteria. The final assay was a qPCR to determine the concentration of the bacteria on the cotton roots after 24 days. QST713 and I-43 1582 were able to colonize the root successfully, with the concentration after 24 days not significantly differing from the concentration at inoculation. This study identifies two bacteria that work systemic resistance and will help aid in implementing these species in an integrated management system.
本研究的目的是确定两种能够控制棉花种群密度的菌株的作用机制。总体目标是：1）确定这些菌株的功效和直接拮抗能力；2）确定这些菌株的系统作用能力。温室试验表明，QST713和I-1582在控制棉苗黄萎病菌方面与化学标准药剂氟吡菌酰胺效果相当。一项试验确定，I-1582及其提取的代谢产物能够通过将死亡率提高到75%以上来直接控制棉苗黄萎病菌的第二阶段幼虫。一项用于确定细菌系统作用能力的分根试验表明，QST713和I-1582能够间接降低线虫种群密度。另一个菌株，菌株2，也表现出系统作用能力，但不是一种成功的生物防治剂，因为它在温室试验和分根试验中支持较高的种群密度。一项逆转录定量聚合酶链反应（RT-qPCR）试验用于确认在分根试验中观察到的任何系统活性。在24小时时，QST713和I-1582都上调了一个参与茉莉酸（JA）合成途径初始阶段的基因，但没有上调另一个参与JA合成后期阶段的基因。这些结果表明，在短期系统反应中，是一种JA中间分子，很可能是OPDA，受到细菌刺激，而不是JA。1周后，这些菌株刺激了一个与水杨酸（SA）反应相关的防御基因。对这些菌株的长期系统反应表明，水杨酸在这些细菌赋予的防御中也发挥了作用。最后的试验是一项定量聚合酶链反应（qPCR），以确定24天后棉花根上细菌的浓度。QST713和I-1582能够成功定殖在根上，24天后的浓度与接种时的浓度没有显著差异。本研究确定了两种具有系统抗性作用的细菌，将有助于在综合管理系统中应用这些菌种。
