Characterization of fludioxonil-resistant and pyrimethanil-resistant phenotypes of Penicillium expansum from apple
Characterization of fludioxonil-resistant and pyrimethanil-resistant phenotypes of Penicillium expansum from apple
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DOI：
10.1094/phyto-98-4-0427
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发表时间：
2008-04-01
期刊：
影响因子：
3.2
通讯作者：
Xiao, C. L.
中科院分区：
文献类型：
--
作者：
Li, H. X.;Xiao, C. L.
苹果采后主要病害之一是青霉病，其主要病原是扩展青霉。咯菌腈和嘧霉胺是美国新注册的梨果采后杀菌剂。为了评估扩展青霉对新的采后杀菌剂的抗性发展的潜在风险，将抗噻菌灵（TBZ-R）和对噻菌灵敏感（TBZ-S）的扩展青霉各一个分离物暴露于UV辐射以产生杀菌剂抗性突变体。测定了4株咯菌腈高抗突变体（EC_（50）> 1,000 μ g/ml）和4株嘧霉胺抗性突变体（EC_（50）> 10 μ g/ml）对噻菌灵、咯菌腈和嘧霉胺的敏感性，以及菌丝生长、PDA产孢、渗透胁迫敏感性、致病性和产孢等适合度参数。在PDA和苹果果实上测定了突变体的抗性稳定性。用3种杀菌剂对苹果蓝霉病的防治效果进行了评价。在亲本野生型菌株及其突变体中，根据其抗性水平鉴定出6种杀菌剂抗性表型。所有4个咯菌腈高抗突变体对嘧霉胺敏感，并保留了与亲本菌株相同的对TBZ的抗性表型。所有4个嘧菌胺抗性突变体对咯菌腈的抗性水平较低，抗性因子> 15。从TBZ-S分离物中分离出的两株嘧霉胺抗性突变株对TBZ的抗性为5 pg/ml。在PDA上连续20代和在苹果果实上连续4代后，突变体保持了与原始世代相同的表型。所有的突变体在0和20摄氏度的苹果果实上都是致病的，但咯菌腈高抗性突变体的毒力较低，产生的分生孢子比嘧霉胺抗性突变体和它们的亲本野生型菌株在苹果果实上。与亲本菌株相比，4株咯菌腈高抗突变体对PDA + NaCl的渗透胁迫敏感性均有所提高，而嘧菌胺抗性突变体对PDA + NaCl的渗透胁迫敏感性无明显变化。嘧霉胺在0 ℃和20 ℃下对咯菌腈抗性突变体引起的蓝霉菌都有效。嘧霉胺和咯菌腈在0 ℃下储存12周期间减少了由嘧霉胺抗性突变体引发的蓝霉菌，但在20 ℃下无效。TBZ在室温下对来自TBZ-S野生型分离物的嘧霉胺抗性突变体无效，但在0 ℃下提供了一些控制。结果表明：（1）适度成本与适生期和致病期的咯菌腈高抗性突变体有关，而与嘧霉胺抗性突变体无关;（2）嘧霉胺在产生抗性的过程中具有比咯菌腈高的风险;和（iii）对三个苹果的三重抗性-如果扩展青霉种群对嘧霉胺产生抗性，则可能出现采后杀菌剂并成为一个实际问题。
Penicillium expansum is the primary cause of blue mold, a major postharvest disease of apple. Fludioxonil and pyrimethanil are two newly registered postharvest fungicides for pome fruit in the United States. To evaluate the potential risk of resistance development in P. expansum to the new postharvest fungicides, one isolate of each of thiabendazole-resistant (TBZ-R) and -sensitive (TBZ-S) P expanstan was exposed to UV radiation to generate fungicide-resistant mutants. Four fludioxonil highly-resistant mutants (EC50 > 1,000 mu g/ml) and four pyrimethanil-resistant mutants (EC50 > 10 mu g/ml) were tested for sensitivities to thiabendazole, fludioxonil, and pyrimethanil, and fitness parameters including mycelial growth, sporulation on potato dextrose agar (PDA), sensitivity to osmotic stress, and pathogenicity and sporulation on apple fruit. The stability of resistance of the mutants was tested on PDA and apple fruit. Efficacy of the three fungicides to control blue mold incited by the mutants wits evaluated on apple fruit. Six fungicide-resistant phenotypes were identified among the parental wild-type isolates and their mutants based upon their resistance levels. All four fludioxonil highly-resistant mutants were sensitive to pyrimethanil and retained the same phenotypes of resistance to TBZ as the parental isolates. All four pyrimethanil-resistant mutants had a low level of resistance to fludioxonil with a resistance factor > 15. The two pyrimethanil-resistant mutants derived from a TBZ-S isolate be-came resistant to TBZ at 5 pg/ml. After 20 successive generations on PDA and four generations on apple fruit, the mutants retained the same phenotypes as the original generations. All mutants were pathogenic on apple fruit at both 0 and 20 degrees C, but fludioxonil highly-resistant mutants were less virulent and produced fewer conidia on apple fruit than pyrimethanil-resistant mutants and their parental wild-type isolates. Compared with the parental isolates, all four fludioxonil highly-resistant mutants had an increased sensitivity to osmotic stress on PDA amended with NaCl, while the pyrimethanil-resistant mutants did not. Pyrimethanil was effective against blue mold caused by fludioxonil-resistant mutants at both 0 and 20 degrees C. Pyrimethanil and fludioxonil reduced blue mold incited by pyrimethanil-resistant mutants during 12-week storage at 0 degrees C but were not effective at 20 degrees C. TBZ was not effective against pyrimethanil-resistant mutants derived from TBZ-S wild-type isolates at room temperature but provided some control at 0 degrees C. The results indicate that: (i) a fitness cost was associated with fludioxonil highly resistant mutants of R expanstan in both saprophytic and pathogenic phases of the pathogen but not pyrimethanil-resistant mutants; (ii) pyrimethanil possessed a higher risk than fludioxonil in the development of resistance in P. expansion; and (iii) triple resistance to the three apple-postharvest fungicides could emerge and become a practical problem if resistance to pyrimethanil develops in P. expansum populations.