花生网斑点(PWB)引起的花生网斑点,是花生最严重的叶面病害之一。虽然丙草胺是一种具有广泛抗真菌谱的活性杀菌剂,它尚未在中国注册控制PWB。目前尚不清楚丙草胺对花生四球菌的活性和对丙草胺的抗性的风险。在目前的研究中,测定丙草胺对96株花生双孢菌的抑制活性,平均EC50值为1.2700±0.7786μg/mL。丙草胺对花生离体叶片具有良好的保护和疗效,效果明显优于相同浓度的多菌灵和苯醚环唑。经丙氯胺处理后,扭曲的花生病菌菌丝,收缩和破裂,随着细胞壁和细胞膜的收缩,增强细胞膜通透性,麦角甾醇含量降低。通过对杀菌剂的适应,共获得了80个抗丙草胺的突变体,频率为6.7×10-3。在PDA平板上转移10次后,所有选择的12种抗丙草胺突变体都失去了对丙草胺的抗性。这些突变体在菌丝生长和致病性方面表现出降低的生物学适应性。此外,丙草胺和其他去甲基化抑制剂(demethylationinhibitoration,简称dmi)杀菌剂之间存在正的交叉抗性,如戊唑醇,曲氟咪唑和苯醚甲环唑,但是在丙草胺和其他类型的杀菌剂之间没有发现交叉抗性,比如多菌灵,吡二氟丁芬或氟敌松。在抗性突变体中检测到PaCYP51和PaAtrB基因的过表达。所有上述结果表明,丙草胺在PWB的管理中具有巨大的潜力。花生双歧杆菌对丙草胺产生抗性的风险相对较低至中等。PaCYP51和PaAtrB的过表达可能与花生四球菌中的丙草胺抗性有关。
Peanut web blotch (PWB) caused by Phoma arachidicola, is one of the most serious foliar diseases of peanut. Although
prochloraz is an active fungicide with broad anti-fungal spectrum, it has not been registered for the control of PWB in China. The activity of
prochloraz against P. arachidicola and the risk of resistance to
prochloraz in P. arachidicola are still unclear. In current study, the inhibitory activity of prochloraz against 96 P. arachidicola strains was determined with the average EC50 value of 1.2700 ± 0.7786 μg/mL. Prochloraz exhibited excellent protective and curative effect on detached peanut leaves, and the effect was obviously better than that of carbendazim and difenoconazole at the same concentration. After prochloraz treatment, the mycelium of P. arachidicola contorted, shrunk and ruptured, with shrinking of cell wall and membrane, enhanced cell membrane permeability, and reduced ergosterol content. Totally 80 prochloraz-resistant mutants were obtained by fungicide adaptation with the frequency of 6.7 × 10-3. All the selected 12
prochloraz-resistant mutants lost their resistance to
prochloraz after 10 transfers on PDA plates. And these mutants exhibited decreased biological fitness in mycelial growth and pathogenicity. Moreover, there was positive cross-resistance between prochloraz and other demethylation inhibitor (DMI) fungicides, such as tebuconazole, triflumizole and difenoconazole, but no cross-resistance was found between prochloraz and other classes of fungicides, such as carbendazim, pydiflumetofen or fludioxonil. Overexpression of PaCYP51 and PaAtrB genes were detected in the resistant mutants. All the above results demonstrated that
prochloraz has a great potential in management of PWB. The risk of P. arachidicola developing resistance to
prochloraz is relatively low-to-medium. Overexpressing of PaCYP51 and PaAtrB might be linked to prochloraz resistance in P. arachidicola.