A Bioassay for Asparagus (Asparagus officinalis L.) Resistance to Stemphylium vesicarium

Purple spot, caused by Stemphylium vesicarium (Wallr.) E. Simmons, is one of the most important diseases facing asparagus producers in Ontario. Four cultivars, Jersey Giant, Guelph Millennium, Guelph Eclipse, and Gijnlim were examined in the field and in detached-spear controlled environment assays for reaction to S. vesicarium infection. Consistent results were achieved in the controlled environment assays and cultivar, location on the spear, isolate, wounding, and lighting were each found to affect lesion formation. In the field, an interaction was identified between cultivar resistance and acute weather, especially heavy rainfall, before and during a critical infection period. In controlled environment studies there was an interaction between cultivar and location of inoculation on the spear, whether near the top or base. The bioassay was useful for assessing some mechanisms of resistance, but inoculating attached spears in the field, while accounting for weather, is recommended for determining realistic field results.

由梨形匍柄霉（Stemphylium vesicarium (Wallr.) E. Simmons）引发的紫斑病（Purple spot），是安大略省芦笋种植者面临的最具危害性的病害之一。本研究选取4个芦笋栽培品种——泽西巨人（Jersey Giant）、圭尔夫千禧（Guelph Millennium）、圭尔夫日食（Guelph Eclipse）与吉恩利姆（Gijnlim），分别通过田间试验与离体嫩茎受控环境试验，评估其对梨形匍柄霉侵染的抗病反应。受控环境试验获得了一致性结果，研究发现栽培品种、嫩茎上的接种位点、病原菌菌株、伤口处理以及光照条件，均会对病斑形成产生显著影响。田间试验则显示，在关键侵染期前后，栽培品种的抗病性与极端天气（尤其是强降雨）之间存在显著交互作用。受控环境研究还证实，栽培品种与嫩茎接种位点（即嫩茎顶端或基部）之间存在交互效应。本研究采用的生物测定法可用于评估部分抗病机制，但为获取更贴合实际生产的田间试验结果，建议在田间对接附于植株的嫩茎进行接种，并结合天气条件开展相关试验。