Sunflower and Plant Biology Research Unit, Edward T. Schafer Agricultural Research Center, USDA-ARS, Fargo, ND 58102.
Plant Dis. 2024 Jun;108(6):1740-1749. doi: 10.1094/PDIS-03-23-0610-RE. Epub 2024 May 22.
Phomopsis stem canker of cultivated sunflower ( L.) can be caused by multiple necrotrophic fungi in the genus , with and being the most common causal agents in the United States. Infection begins at the leaf margins and proceeds primarily through the vasculature, progressing from the leaf through the petiole to the stem, resulting in formation of brown stem lesions centered around the petiole. Sunflower resistance to Phomopsis stem canker is quantitative and genetically complex. Due to the intricate disease process, resistance is possible at different stages of infection, and multiple forms of defense may contribute to the overall level of quantitative resistance. In this study, sunflower lines exhibiting field resistance to Phomopsis stem canker were evaluated for stem and leaf resistance to multiple isolates of and in greenhouse experiments, and responses to the two species were compared. Additionally, selected resistant and susceptible lines were evaluated for petiole transmission resistance to . Lines with distinct forms of resistance were identified, and results indicated that responses to stem inoculation were strongly correlated (Spearman's coefficient 0.598, < 0.001) for the two fungal species, while leaf responses were not (Spearman's coefficient 0.396, = 0.076). These results provide a basis for genetic dissection of distinct forms of sunflower resistance to Phomopsis stem canker and will facilitate combining different forms of resistance to potentially achieve durable control of this disease in sunflower hybrids.
栽培向日葵的拟茎点溃疡病可由 属中的多种坏死型真菌引起，其中 和 是美国最常见的致病因子。感染始于叶片边缘，主要通过维管束进行，从叶片经叶柄扩展到茎，导致叶柄周围形成棕色的茎部病斑。向日葵对拟茎点溃疡病的抗性是数量性状的，遗传复杂。由于疾病过程复杂，在感染的不同阶段可能具有抗性，并且多种形式的防御可能有助于整体的数量抗性水平。在这项研究中，对表现田间抗性的向日葵品系进行了温室试验，评估了它们对 和 多种分离株的茎和叶抗性，并比较了这两个物种的反应。此外，还对选定的抗性和敏感品系进行了叶柄对 的传病抗性评估。鉴定出具有不同抗性形式的品系，结果表明，对两种真菌的茎接种反应呈强相关性（Spearman 系数 0.598， < 0.001），而叶片反应则没有相关性（Spearman 系数 0.396， = 0.076）。这些结果为向日葵对拟茎点溃疡病的不同抗性形式的遗传解析提供了基础，并将有助于结合不同形式的抗性，以实现向日葵杂种中对该病害的持久控制。
