Abstract

Root rot is an important disease of field pea (Pisum sativum L.) on the Canadian Prairies. The composition and alternative crop hosts of fungal and oomycete communities colonizing pea residues from Alberta and Manitoba were studied in field trials over two years. Standing pea residues were sampled from diseased and asymptomatic patches of 17 commercial fields in 2013 and 2014 after harvest and again in early spring the following year prior to seeding. The pea residue was ground to a powder and mixed with sterile Cornell potting mix. Plants of pea, wheat, and canola were grown in this mixture under controlled conditions. The root rot severity on each plant was evaluated and sections from diseased roots were plated on agar medium. Fungal and oomycete communities isolated from symptomatic roots were identified based on culture morphology and PCR analysis. About 3000 fungal isolates, belonging to some 50 species, were identified. Canola was less susceptible to infection than pea or wheat. Fusarium avenaceum (Fr.) Sacc. was the most abundant species infecting the three hosts; F. culmorum (Wm.G.Sm.) Sacc. and Bipolaris sorokiana (Sacc.) Shoemaker were more frequently isolated from wheat, and F. solani (Mart.) Sacc., F. oxysporum Schlecht. and Aphanomyces euteiches Drechsler were more frequently isolated from pea. Pathogen communities from asymptomatic and diseased patches of fields were similar. Overall, composition of the fungal community changed over winter, but the most abundant species did not change. The results show that multiple pathogens, and particularly Fusarium spp., can survive overwinter on pea residue.

摘要

根腐病是豌豆（Pisum sativum）的重要病害L.）在加拿大大草原上。在两年多的田间试验中，研究了定居在艾伯塔省和马尼托巴省豌豆残留物的真菌和卵菌群落的组成和替代作物宿主。2013 年和 2014 年收获后和第二年早春播种前再次从 17 个商业田地的患病和无症状斑块中对立豌豆残留物进行采样。将豌豆残渣研磨成粉末并与无菌康奈尔盆栽混合物混合。在受控条件下，豌豆、小麦和油菜植物在这种混合物中生长。评估每株植物的根腐病严重程度，并将患病根的切片铺在琼脂培养基上。从有症状的根中分离出的真菌和卵菌群落基于培养形态学和 PCR 分析进行鉴定。大约 3000 个真菌分离株，约 50 种，已被鉴定。与豌豆或小麦相比，双低油菜籽不易受感染。Fusarium avenaceum (Fr.) Sacc。是感染三种宿主的最丰富的物种；F. culmorum (Wm.G.Sm.) Sacc。和Bipolaris sorokiana (Sacc.) Shoemaker 更频繁地从小麦中分离出来，而F. solani (Mart.) Sacc., F. oxysporum Schlecht。和Aphanomyces euteiches Drechsler 更频繁地从豌豆中分离出来。来自无症状和患病田地的病原体群落是相似的。总体而言，真菌群落的组成在冬季发生了变化，但最丰富的物种没有变化。结果表明，多种病原体，尤其是镰刀菌属，可以在豌豆残渣上越冬。