Table_7_Intensified Pulse Rotations Buildup Pea Rhizosphere Pathogens in Cereal and Pulse Based Cropping Systems.DOCX

The association of plants and microbial communities is crucial for crop production, and host plants influence the composition of rhizosphere microbiomes. Pulse crops play an important role in the development of sustainable cropping systems, and producers in the Canadian prairies often increase the frequency of pulses in their cropping systems. In this study, we determined the shifts in the fungal community of pea (Pisum sativum L.) rhizosphere, as influenced by the frequency of pulses in rotation, using high throughput sequencing. Six cropping systems containing pea (P), lentil (Lens culinaris Medik., L), hybrid canola (Brassica napus L., C), wheat (Triticum aestivum L., W), and oat (Avena sativa L., O) in different intensities were tested. The fungal communities were assessed at the flowering stage in the fourth and fifth year of the 4-year rotations. Cropping system had a significant impact on the composition of the rhizosphere fungal community, and the effect of crop rotation sequence was greater and explained more of the variation than the effect of previous crops. The rotation with consecutive pulses (WPLP) decreased fungal evenness and increased the proportion of pathotrophs. Fusarium was a dominant and ubiquitous pathotrophic genus. Olpidium virulentus, Botrytis cinerea, Fusarium solani, F. graminearum, and Alternaria eichhorniae were generally more abundant in pulse intensive rotations (WPLP, WLOP, and WPOP), the exception being F. solani which was not promoted by lentil. Reads of O. virulentus and B. cinerea were most abundant in pea preceded by lentil followed by the reads of Mortierella elongata in pea preceded by wheat. Pea consistently had higher grain yield when grown in diversified rotations including wheat, canola/lentil, and oat than rotations with two repeated crops (canola or pea). Cropping system affected the soil physicochemical properties, and soil pH was the main driver of fungal community shift. No evidence of beneficial microorganisms involvement in plant productivity was observed, but the high abundance of pathotrophs in pulse intensified rotations suggests the possibility of pathogen buildup in the soil with increasing pulse frequency. Diversifying rotation sequences minimized disease risk and increased pea production, in this study. Careful selection of plant species appears as a strategy for the management of rhizosphere fungal communities and the maintenance of crop production system’s health.

植物与微生物群落的互作对于作物生产至关重要，宿主植物可影响根际微生物组（rhizosphere microbiomes）的组成结构。豆科作物（Pulse crops）在可持续种植体系的构建中发挥关键作用，加拿大草原地区的种植者常提升其种植体系中豆科作物的种植频率。本研究采用高通量测序（High Throughput Sequencing）技术，解析了轮作豆科作物种植频率对豌豆（*Pisum sativum* L.）根际真菌群落动态的调控效应。本试验共设置6种不同种植强度的轮作体系，包含豌豆（P）、小扁豆（*Lens culinaris* Medik.，L）、杂交油菜（*Brassica napus* L.，C）、普通小麦（*Triticum aestivum* L.，W）与燕麦（*Avena sativa* L.，O）5种供试作物，对各体系展开分析。在4年轮作周期的第4年及第5年的开花期，对各体系的根际真菌群落进行采样评估。轮作体系对根际真菌群落组成具有显著影响，且轮作序列的调控效应显著强于前茬作物的影响，可解释更多的群落变异来源。连作豆科作物的轮作模式（WPLP）会降低真菌群落的均匀度，并提升致病营养型真菌（pathotrophs）的占比。镰孢菌属（Fusarium）是优势且广布的致病营养型真菌类群。高豆科作物种植频率的轮作体系（WPLP、WLOP及WPOP）中，毒性油壶菌（*Olpidium virulentus*）、灰葡萄孢（*Botrytis cinerea*）、茄镰孢（*Fusarium solani*）、禾谷镰孢（*F. graminearum*）及凤眼莲链格孢（*Alternaria eichhorniae*）的相对丰度普遍更高，仅茄镰孢例外——小扁豆种植并不会提升其相对丰度。以小扁豆为前茬的豌豆种植体系中，毒性油壶菌与灰葡萄孢的测序读段（Reads）丰度最高；而以小麦为前茬的豌豆体系中，长孢被孢霉（*Mortierella elongata*）的测序读段丰度紧随其后。与仅连作两种作物（油菜或豌豆）的轮作体系相比，涵盖小麦、油菜/小扁豆及燕麦的多样化轮作体系中，豌豆的籽粒产量始终更高。轮作体系对土壤理化性质具有显著调控作用，其中土壤pH是驱动根际真菌群落变化的核心因子。本研究未观测到有益微生物对作物产量存在正向调控作用，但高豆科作物种植频率的轮作体系中致病营养型真菌丰度较高，这表明随着豆科作物种植频率提升，土壤中病原物累积的风险可能增加。本研究证实，优化轮作序列的多样性可降低病害风险并提升豌豆生产效益。合理筛选作物种类，可作为调控根际真菌群落结构、维持作物生产体系健康的有效策略。