Department of Plant Pathology, University of Wisconsin-Madison, 1630 Linden Dr., Madison 53706.
Phytopathology. 2019 Mar;109(3):436-445. doi: 10.1094/PHYTO-06-18-0181-R. Epub 2019 Jan 11.
Early blight, caused by Alternaria solani, along with brown spot, caused by A. alternata, have the potential to reduce quality and yield in potato production globally. Prior to this study, the incidence, disease impact, and fungicide resistance attributes of A. alternata in Wisconsin were poorly understood. Potato pathogens were isolated from foliar lesions at three commercial locations in Wisconsin in 2012 and 2017 and were initially morphologically identified as A. solani (n = 33) and A. alternata (n = 40). Identifications were further corroborated with the phylogenetic analysis of the internal transcribed spacer (ITS), translation elongation factor 1 (TEF1), gapdh, Alt a 1, and OPA10-2. A multigene phylogeny of ITS, TEF1, gapdh, and Alt a 1 showed five genotypes of A. alternata and one single genotype of A. solani. We demonstrated that the A. alternata isolates were virulent on potato cultivars Russet Burbank (P < 0.013) and Atlantic (P < 0.0073), though they caused less disease than A. solani (P < 0.0001 and P < 0.0001, respectively). A. alternata caused little disease on the breeding line 24-24-12 (P = 0.9929), and A. solani caused fewer disease symptoms on 24-24-12 than on Russet Burbank (P < 0.0001) or Atlantic (P < 0.0001). Breeding line 24-24-12 may be a promising source of potential resistance for the two diseases. There was no significant difference in virulence of different A. alternata genotypes, and no significant difference in virulence or genotype clustering among isolates from the three locations. Isolates of A. alternata that induced chlorosis caused larger lesion areas than isolates that did not in Russet Burbank (P < 0.0001), Atlantic (P < 0.0001), and 24-24-12 (P = 0.0365). There was no significant difference in virulence between quinone outside inhibitor (QoI)-sensitive and QoI-resistant isolates of A. alternata. This study enhanced our understanding of potato early blight and brown spot in Wisconsin, and suggested that A. alternata in addition to A. solani should be carefully monitored and possibly uniquely managed in order to achieve overall disease control.
早疫病由茄链格孢（Alternaria solani）引起，而褐斑病由交链格孢（A. alternata）引起，它们有可能降低全球马铃薯生产的质量和产量。在这项研究之前，威斯康星州的 A. alternata 的发病率、疾病影响和抗药性特征了解甚少。2012 年和 2017 年，在威斯康星州的三个商业地点从叶片病斑中分离出马铃薯病原菌，最初形态学鉴定为茄链格孢（n = 33）和交链格孢（n = 40）。通过对内部转录间隔区（ITS）、翻译延伸因子 1（TEF1）、gapdh、Alt a 1 和 OPA10-2 的系统发育分析进一步证实了这些鉴定。ITS、TEF1、gapdh 和 Alt a 1 的多基因系统发育表明，有 5 种 A. alternata 基因型和 1 种 A. solani 基因型。我们证明，A. alternata 分离株对马铃薯品种 Russet Burbank（P < 0.013）和 Atlantic（P < 0.0073）具有毒力，但它们引起的疾病比 A. solani 少（P < 0.0001 和 P < 0.0001，分别）。A. alternata 对育种系 24-24-12 的病害影响较小（P = 0.9929），而 A. solani 对 24-24-12 的病害症状比 Russet Burbank（P < 0.0001）或 Atlantic（P < 0.0001）少。24-24-12 可能是这两种疾病潜在抗性的有希望的来源。不同 A. alternata 基因型的毒力没有显著差异，三个地点分离株的毒力或基因型聚类也没有显著差异。在 Russet Burbank（P < 0.0001）、Atlantic（P < 0.0001）和 24-24-12（P = 0.0365）中，引起黄化的 A. alternata 分离株比不引起黄化的分离株引起的病斑面积更大。A. alternata 的敏感和抗性醌外抑制剂（QoI）分离株之间的毒力没有显著差异。这项研究增强了我们对威斯康星州马铃薯早疫病和褐斑病的认识，并表明除了 A. solani 之外，还应仔细监测 A. alternata，并可能需要单独管理，以实现总体疾病控制。
