Mavrodi Dmitri V, Mavrodi Olga V, Elbourne Liam D H, Tetu Sasha, Bonsall Robert F, Parejko James, Yang Mingming, Paulsen Ian T, Weller David M, Thomashow Linda S
Department of Biological Sciences, University of Southern Mississippi, Hattiesburg, MS, United States.
Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, NSW, Australia.
Front Plant Sci. 2018 Mar 21;9:345. doi: 10.3389/fpls.2018.00345. eCollection 2018.
The Inland Pacific Northwest (IPNW) encompasses 1. 6 million cropland hectares and is a major wheat-producing area in the western United States. The climate throughout the region is semi-arid, making the availability of water a significant challenge for IPNW agriculture. Much attention has been given to uncovering the effects of water stress on the physiology of wheat and the dynamics of its soilborne diseases. In contrast, the impact of soil moisture on the establishment and activity of microbial communities in the rhizosphere of dryland wheat remains poorly understood. We addressed this gap by conducting a three-year field study involving wheat grown in adjacent irrigated and dryland (rainfed) plots established in Lind, Washington State. We used deep amplicon sequencing of the V4 region of the 16S rRNA to characterize the responses of the wheat rhizosphere microbiome to overhead irrigation. We also characterized the population dynamics and activity of indigenous Phz rhizobacteria that produce the antibiotic phenazine-1-carboxylic acid (PCA) and contribute to the natural suppression of soilborne pathogens of wheat. Results of the study revealed that irrigation affected the Phz rhizobacteria adversely, which was evident from the significantly reduced plant colonization frequency, population size and levels of PCA in the field. The observed differences between irrigated and dryland plots were reproducible and amplified over the course of the study, thus identifying soil moisture as a critical abiotic factor that influences the dynamics, and activity of indigenous Phz communities. The three seasons of irrigation had a slight effect on the overall diversity within the rhizosphere microbiome but led to significant differences in the relative abundances of specific OTUs. In particular, irrigation differentially affected multiple groups of and , including taxa with known plant growth-promoting activity. Analysis of environmental variables revealed that the separation between irrigated and dryland treatments was due to changes in the water potential (Ψ) and pH. In contrast, the temporal changes in the composition of the rhizosphere microbiome correlated with temperature and precipitation. In summary, our long-term study provides insights into how the availability of water in a semi-arid agroecosystem shapes the belowground wheat microbiome.
内陆太平洋西北地区（IPNW）涵盖160万公顷农田，是美国西部的一个主要小麦产区。该地区气候半干旱，水资源的可利用性对IPNW农业构成重大挑战。人们对揭示水分胁迫对小麦生理和土传病害动态的影响给予了很多关注。相比之下，土壤湿度对旱地小麦根际微生物群落的建立和活性的影响仍知之甚少。我们通过在华盛顿州林德建立的相邻灌溉田和旱地（雨养）地块上种植小麦，进行了为期三年的田间研究，以填补这一空白。我们使用16S rRNA V4区域的深度扩增子测序来表征小麦根际微生物群对地面灌溉的反应。我们还表征了产生抗生素吩嗪-1-羧酸（PCA）并有助于自然抑制小麦土传病原体的本地Phz根际细菌的种群动态和活性。研究结果表明，灌溉对Phz根际细菌产生了不利影响，这从田间植物定殖频率、种群大小和PCA水平的显著降低中可以明显看出。灌溉田和旱地之间观察到的差异是可重复的，并且在研究过程中有所放大，从而确定土壤湿度是影响本地Phz群落动态和活性的关键非生物因素。三个季节的灌溉对根际微生物群的整体多样性影响较小，但导致特定OTU的相对丰度存在显著差异。特别是，灌溉对多个 和 组有不同影响，包括具有已知促植物生长活性的分类群。环境变量分析表明，灌溉处理和旱地处理之间的分离是由于水势（Ψ）和pH值的变化。相比之下，根际微生物群组成的时间变化与温度和降水相关。总之，我们的长期研究深入了解了半干旱农业生态系统中的水资源可利用性如何塑造地下小麦微生物群。
