禾谷镰刀菌对苯基吡咯类杀菌剂咯菌腈的抗性机制

由禾谷镰刀菌引起的小麦赤霉病是世界小麦生产上的重要真菌病害。为了进一步明确禾谷镰刀菌对苯基吡咯类杀菌剂咯菌腈产生抗性的机制，本文以前期室内通过药剂驯化方式得到的4株禾谷镰刀菌对咯菌腈的高水平抗性突变体 (其抗性倍数在318.2~782.9之间) 为主要研究材料，采用生物测定及分子生物学等方法开展了禾谷镰刀菌对咯菌腈的抗性机制研究。结果表明:供试禾谷镰刀菌抗咯菌腈突变体对小麦幼穗的致病力降低了约50%，部分菌株 (2XZ-4R) 甚至完全丧失了对小麦的致病能力；抗性突变体对渗透胁迫 (0.5 mol/L NaCl, 1.0 mol/L MgCl₂, 1.0 mol/L葡萄糖或1.0 mol/L甘露醇) 高度敏感，且菌丝生长抑制率较敏感菌株降低约50%以上，表明其环境适合度显著下降。同时，抗性突变体中苯丙氨酸解氨酶 (PAL)、过氧化物酶 (POD) 和多酚氧化酶 (PPO) 活性较敏感菌株均升高2倍以上。分子生物学分析发现，供试抗性突变体中候选靶标基因 (FgOs1和FgOs5) 的表达量显著下调 (P<0.05)，推测FgOs1和FgOs5可能参与了禾谷镰刀菌对咯菌腈抗性的形成过程。总之，该研究探究了禾谷镰刀菌抗咯菌腈突变体的生物学特性，并为深入揭示禾谷镰刀菌对咯菌腈的抗性分子机制提供了新的思路。

Mechanism of Fusarium graminearum resistant to the phenylpyrrole fungicide fludioxonil

The Fusarium head blight (FHB) caused by Fusarium graminearum, is one of the most notorious diseases during wheat production throughout the world. In this paper, four fludioxonil-resistant mutants (the resistance rate ranged from 318.2 to 782.9) generated by exposure to fludioxonil under laboratory conditions were used as the main research materials to uncover the resistant mechanism of F. graminearum to fludioxonil by biological and molecular biology approaches. All of the resistant mutants were found to have reduced pathogenicity to wheat by about 50% compared to sensitive isolates, especially 2XZ-4R, exhibiting a complete loss of pathogenicity on wheat ears. Meanwhile, all of the mutants were highly sensitive to osmotic stress (0.5 mol/L NaCl, 1.0 mol/L MgCl₂, 1.0 mol/L glucose, or 1.0 mol/L mannitol), and the inhibition rates of mycelial growth were reduced by more than 50% compared to sensitive isolates, indicating that its fitness cost associated with fludioxonil resistance. Furthermore, PAL, POD, and PPO activities of the resistant mutants were increased more than two-fold compared to that of the sensitive isolates. Molecular biology analysis found the expression of the proposed fludioxonil target genes (FgOs1 and FgOs5) were significantly reduced (P＜0.05) in the resistant mutants, indicating that FgOs1 and FgOs5 may be involved in the formation of F. graminearum resistant to fludioxonill. In conclusion, this study explored the biological characteristics of F. graminearum resistant to fludioxonil, and provide new insight into the molecular resistant mechanism of F. graminearum to fludioxonil.