Department of Plant Pathology, Federal University of Lavras, Lavras, Brazil.
Department of Crop Protection, Agricultural Engineering and Soils São Paulo State University, São Paulo, Brazil.
Pest Manag Sci. 2022 Dec;78(12):5251-5258. doi: 10.1002/ps.7144. Epub 2022 Sep 12.
Quinone outside inhibitor (QoI) fungicides have not been effective in controlling the wheat blast disease [Pyricularia oryzae Triticum lineage (PoTl)] in Brazil. The first report of resistance of PoTl to QoIs in this country occurred in 2015. This study aimed to test hypotheses about the changes in fitness parameters and competitive advantage of the QoI-resistant (R) PoTl isolate group compared to the sensitive (S) isolate group. Mycelial growth on PDA medium and in vivo conidial production, incubation period and disease severity were analyzed as fitness parameters. The competitive ability was measured on wheat leaves and heads inoculated with mixtures of R:S isolates at the following proportions: 0S:100R, 20S:80R, 50S:50R, 80S:20R, 100S:0R, and 0S:0R.
The QoI-R isolate group had significantly higher fitness than the sensitive isolate group, considering both in vitro and in vivo parameters. The highest in vivo conidial production on wheat leaves and the highest leaf and head disease severity were detected when resistant strains were predominant in the isolate's mixtures (20S:80R or 0S:100R proportions), in the absence of fungicide pressure. Conidia harvested from wheat blast lesions on leaves inoculated with 20S:80R and 0S:100R mixtures were resistant to QoIs in vitro assays based on discriminatory doses of the fungicide.
Therefore, QoI resistance facilitated a higher fitness and a competitive advantage in PoTl, which contrasts with the evolutionary theory that associates a fitness cost to fungicide resistance. We discuss the evolutionary and ecological implications of the higher fitness as found in the fungicide-resistant adapted populations of the wheat blast pathogen. © 2022 Society of Chemical Industry.
醌外抑制剂（QoI）杀菌剂在巴西未能有效控制小麦叶枯病[Pyricularia oryzae Triticum 谱系（PoTl）]。该国首次报道 PoTl 对 QoI 的抗药性是在 2015 年。本研究旨在检验关于 QoI 抗性（R）PoTl 分离株组与敏感（S）分离株组相比，适应过程中适应性参数和竞争优势变化的假设。在 PDA 培养基上和体内产分生孢子、潜伏期和疾病严重程度等方面进行了分析。在小麦叶片和头部接种 R:S 分离株混合物（0S:100R、20S:80R、50S:50R、80S:20R、100S:0R 和 0S:0R）时，测量了竞争能力。
考虑到体外和体内参数，QoI-R 分离株组的适应性明显高于敏感分离株组。在分离株混合物中（20S:80R 或 0S:100R 比例）抗性菌株占优势时，在没有杀菌剂压力的情况下，体内产分生孢子量最高，小麦叶片上的产分生孢子量最高，叶片和头部病害严重程度最高。接种 20S:80R 和 0S:100R 混合物的叶片上小麦叶枯病病斑上收获的分生孢子对 QoI 具有抗药性，这是基于杀菌剂的区分剂量进行的体外测定。
因此，QoI 抗性使 PoTl 的适应性和竞争力提高，这与将杀菌剂抗性与适应成本相关联的进化理论相反。我们讨论了在小麦叶枯病病原体的适应种群中发现的更高适应性所带来的进化和生态影响。© 2022 化学工业协会。
