Phytopathology. 2014 Apr;104(4):347-56. doi: 10.1094/PHYTO-07-13-0208-R.
Respiration inhibitors such as the succinate dehydrogenase inhibitors (SDHIs) and the quinone outside inhibitors (QoIs) are fungicide classes with increasing relevance in gray mold control. However, recent studies have shown that dual resistance to both fungicide classes is a common trait in Botrytis cinerea populations from several hosts throughout the world. Resistance of B. cinerea to SDHIs is associated with several mutations in the sdhB, sdhC, and sdhD genes, while resistance to QoIs, in most cases, is associated with the G143A mutation in the cytb gene. The objective of the current study was to investigate the fitness and the competitive ability of B. cinerea field strains possessing one of the H272Y/R/L, N230I, or P225F sdhB substitutions and the G143A mutation of cytb. Fitness parameters measured were (i) mycelial growth and conidia germination in vitro, (ii) aggressiveness and sporulation capacity in vivo, (iii) sclerotia production in vitro and sclerotia viability under different storage conditions, and (iv) sensitivity to oxidative stress imposed by diquat treatments. The competitive ability of the resistant isolates was measured in the absence and presence of the SDHI fungicides boscalid and fluopyram selection pressure. The measurements of individual fitness components showed that the H272R/G143A isolates had the lower differences compared with the sensitive isolates. In contrast, the groups of H272Y/L/G143A, N230I/G143A, and P225F/G143A isolates showed reduced fitness values compared with the sensitive isolates. Isolates possessing only the cytb G143A substitution did not show any fitness cost. The competition experiments showed that, in the absence of fungicide selection pressure, after four disease cycles on apple fruit, the sensitive isolates dominated in the population in all the mixtures tested. In contrast, when the competition experiment was conducted under the selection pressure of boscalid, a gradual decrease in the frequency of sensitive isolates was observed, whereas the frequency of H272L and P225F isolates was increased. When the competition experiment was conducted in the presence of fluopyram, the sensitive isolates were eliminated even after the first disease cycle and the P225F mutants dominated in the population. Such results suggest that the sdhB mutations may have adverse effects on the mutants. The observed dominance of sensitive isolates in the competition experiments conducted in the absence of fungicides suggest that the application of SDHIs in alternation schemes may delay the selection or reduce the frequency of SDHI-resistant mutants.
呼吸抑制剂，如琥珀酸脱氢酶抑制剂（SDHIs）和醌外抑制剂（QoIs），是在灰霉病防治中越来越重要的杀菌剂类别。然而，最近的研究表明，对这两类杀菌剂的双重抗性是来自世界各地多种宿主的 Botrytis cinerea 种群的共同特征。B. cinerea 对 SDHIs 的抗性与 sdhB、sdhC 和 sdhD 基因中的几个突变有关，而对 QoIs 的抗性，在大多数情况下，与 cytb 基因中的 G143A 突变有关。本研究的目的是研究具有 H272Y/R/L、N230I 或 P225F sdhB 取代和 cytb G143A 突变之一的 B. cinerea 田间菌株的适应性和竞争能力。测量的适应性参数为：（i）体外菌丝生长和孢子萌发，（ii）体内侵袭性和产孢能力，（iii）体外产菌核和不同储存条件下菌核活力，以及（iv）二氯喹啉处理引起的氧化应激敏感性。在没有和存在 SDHI 杀菌剂 boscalid 和 fluopyram 选择压力的情况下，测量了抗性分离株的竞争能力。单个适应性成分的测量表明，与敏感分离株相比，H272R/G143A 分离株的差异较小。相比之下，H272Y/L/G143A、N230I/G143A 和 P225F/G143A 分离株组与敏感分离株相比，适应性值较低。仅具有 cytb G143A 取代的分离株没有表现出任何适应性成本。竞争实验表明，在没有杀菌剂选择压力的情况下，在苹果果实上进行四个疾病周期后，在所有测试的混合物中，敏感分离株在种群中占主导地位。相比之下，当在 boscalid 的选择压力下进行竞争实验时，观察到敏感分离株的频率逐渐降低，而 H272L 和 P225F 分离株的频率增加。当在 fluopyram 存在的情况下进行竞争实验时，即使在第一个疾病周期后，敏感分离株也被消除，而 P225F 突变体在种群中占主导地位。这些结果表明，sdhB 突变可能对突变体有不利影响。在没有杀菌剂的竞争实验中观察到敏感分离株的优势表明，SDHI 在交替方案中的应用可能会延迟选择或降低 SDHI 抗性突变体的频率。
