Plant Pathology & Plant-Microbe Biology Section, School of Integrative Plant Science, Cornell University, Geneva, NY 14456, U.S.A.
Departamento de Fitopatologia, Universidade Federal de Viçosa, 36570-900, Viçosa, MG, Brazil.
Plant Dis. 2022 Feb;106(2):360-363. doi: 10.1094/PDIS-06-21-1234-SC. Epub 2022 Feb 9.
The infection of the floral tissues of snap bean and other crops by , the causative agent of white mold, is by ascospores. Irrespective of the fungicide mode of action being evaluated, in vitro fungicide sensitivity tests are conducted almost exclusively using mycelial growth assays. This is likely because of difficulties and time involved in sclerotial conditioning required to produce apothecia and ascospores. The objective of this research was to compare estimates of fungicide sensitivity between mycelial growth and ascospore germination assays for . Sensitivity assays were conducted using serial doses of three fungicides commonly used to control white mold: boscalid, fluazinam, and thiophanate-methyl. A total of 27 isolates were evaluated in replicated trials conducted for each fungicide and assay type. The effective concentration to reduce mycelial growth or ascospore germination by 50% (EC) was estimated for each isolate, fungicide, and assay type. The median EC values obtained from ascospore germination assays were 52.7, 10.0, and 2.7 times higher than those estimated from the mycelial growth for boscalid, fluazinam, and thiophanate-methyl, respectively. No significant correlation was found between EC values estimated by the two methods. These findings highlight differences that may be important in evaluating the sensitivity of given the fungicide mode of action and how they will be used in the field.
菜豆和其他作物的花朵组织被引起白霉病的侵染，是通过子囊孢子。无论评估的杀菌剂作用模式如何，体外杀菌剂敏感性测试几乎都仅使用菌丝生长测定法进行。这可能是因为产生子囊壳和子囊孢子所需的菌核条件处理既困难又耗时。本研究的目的是比较子囊孢子萌发测定法和菌丝生长测定法对的杀菌剂敏感性估计值。使用三种常用于防治白霉病的杀菌剂：肟菌酯、咯菌腈和甲基硫菌灵的连续剂量进行了敏感性测定。在每个杀菌剂和测定类型的重复试验中评估了总共 27 个分离物。对于每个分离物、杀菌剂和测定类型，都估计了抑制菌丝生长或子囊孢子萌发 50%的有效浓度 (EC)。从子囊孢子萌发测定法获得的中位 EC 值分别比肟菌酯、咯菌腈和甲基硫菌灵的菌丝生长法估计值高 52.7、10.0 和 2.7 倍。这两种方法估计的 EC 值之间没有发现显著相关性。这些发现强调了在评估给定杀菌剂作用模式和它们将如何在田间使用时，敏感性可能存在的差异，这一点很重要。
