Department of Plant Pathology, University of Georgia, Griffin, GA 30223.
Department of Plant Pathology, University of Georgia, Tifton, GA 31793.
Plant Dis. 2021 Oct;105(10):2946-2954. doi: 10.1094/PDIS-02-21-0236-RE. Epub 2021 Oct 26.
Frogeye leaf spot (FLS), caused by the fungal pathogen K. Hara, is a foliar disease of soybean ( L. [Merr.]) responsible for yield reductions throughout the major soybean-producing regions of the world. In the United States, management of FLS relies heavily on the use of resistant cultivars and in-season fungicide applications, specifically within the class of quinone outside inhibitors (QoIs), which has resulted in the development of fungicide resistance in many states. In 2018 and 2019, 80 isolates of were collected from six counties in Georgia and screened for QoI fungicide resistance using molecular and in vitro assays, with resistant isolates being confirmed from three counties. Additionally, 50 isolates, including a "baseline isolate" with no prior fungicide exposure, were used to determine the percent reduction of mycelial growth to two fungicides, azoxystrobin and pyraclostrobin, at six concentrations: 0.0001, 0.001, 0.01, 0.1, 1, and 10 μg ml. Mycelial growth observed for resistant isolates varied significantly from both sensitive isolates and baseline isolate for azoxystrobin concentrations of 10, 1, 0.1, and 0.01 μg ml and for pyraclostrobin concentrations of 10, 1, 0.1, 0.01, and 0.001 μg ml. Moreover, 40 isolates were used to evaluate pathogen race on six soybean differential cultivars by assessing susceptible or resistant reactions. Isolate reactions suggested 12 races of present in Georgia, 4 of which have not been previously described. Species richness indicators (rarefaction and abundance-based coverage estimators) indicated that within-county race numbers were undersampled in this study, suggesting the potential for the presence of either additional undescribed races or known but unaccounted for races in Georgia. However, no isolates were pathogenic on 'Davis', a differential cultivar carrying the resistance allele, suggesting that the gene is still an effective source of resistance in Georgia.
蛙眼病叶斑病（FLS）由真菌病原体 K. Hara 引起，是一种大豆叶片病害，可导致世界主要大豆产区的产量下降。在美国，FLS 的管理主要依赖于使用抗性品种和季节性杀菌剂应用，特别是在醌外抑制剂（QoI）类中，这导致许多州的杀菌剂抗性发展。2018 年和 2019 年，从佐治亚州的六个县采集了 80 个 K. 的分离株，并使用分子和体外测定法对 QoI 杀菌剂抗性进行了筛选，从三个县确认了抗性分离株。此外，使用 50 个分离株，包括一个没有先前接触过杀菌剂的“基线分离株”，来确定两种杀菌剂，肟菌酯和吡唑醚菌酯，在六个浓度下对菌丝生长的抑制率：0.0001、0.001、0.01、0.1、1 和 10μg ml。对于肟菌酯浓度为 10、1、0.1 和 0.01μg ml 以及吡唑醚菌酯浓度为 10、1、0.1、0.01 和 0.001μg ml 的抗性分离株，观察到的菌丝生长与敏感分离株和基线分离株有显著差异。此外，使用 40 个分离株评估了在六种大豆差异品种上病原菌的毒力，方法是评估敏感或抗性反应。分离株的反应表明，佐治亚州存在 12 种 K. ，其中 4 种以前没有描述过。物种丰富度指标（稀疏和基于丰度的覆盖估计）表明，在本研究中，各县内的 毒力数量抽样不足，这表明佐治亚州可能存在其他未描述的毒力或已知但未被记录的毒力。然而，没有分离株对携带 抗性等位基因的差异品种 '戴维斯'致病，这表明该基因在佐治亚州仍然是一种有效的抗性来源。
