灰葡萄孢对氟啶胺的敏感性检测及敏感性降低菌株生物学性状研究

为评价灰霉病菌对氟啶胺的敏感性及抗药性风险，本试验于2020年-2021年在吉林、江西、湖北、山东、北京、湖南等地区的草莓、辣椒、四季豆、茄子和番茄上采集病叶、病茎、病花和病果，经单孢分离获得117个灰葡萄孢Botrytis cinerea菌株，采用菌丝生长速率法测定其对氟啶胺的敏感性。结果表明：有4株灰葡萄孢BJ14、BJ45、BJ46和BJ47对氟啶胺的敏感性显著降低，EC₅₀在0.113 7～0.394 6μg/mL,抗性倍数为4.7～16.3,MIC值>4μg/mL。其余113个菌株对氟啶胺的平均EC₅₀为0.025 1μg/mL。敏感性降低的4个菌株继代培养10代后，抗药性状稳定。交互抗性测定结果表明，对氟啶胺敏感性下降的菌株对腐霉利和咯菌腈2种杀菌剂表现为敏感，氟啶胺与腐霉利或咯菌腈没有交互抗性。生物学性状研究表明，4株敏感性下降菌株在PDA平板上的生长速率和在番茄果实上的致病力都显著低于敏感菌株，而菌丝生物量、产孢量和孢子萌发率与敏感菌株无显著差异。以上研究结果表明，田间已存在对氟啶胺敏感性降低的菌株，鉴于灰葡萄孢属于高风...     

拟轮枝镰孢对多菌灵的敏感性及抗性菌株生物学性状和交互抗性

为评价玉米穗腐病主要致病菌拟轮枝镰孢Fusarium verticillioides对多菌灵的敏感性，采用菌丝生长速率法测定了采自山东、河北、河南、四川、甘肃、辽宁及宁夏7省(自治区)的168株玉米穗腐病拟轮枝镰孢对多菌灵的敏感性，并对经药剂驯化获得的拟轮枝镰孢抗多菌灵菌株主要生物学性状和交互抗性进行了研究。结果表明:多菌灵抑制拟轮枝镰孢菌丝生长的EC₅₀值在0.013 2~0.774 0 mg/L之间，平均EC₅₀值为(0.220 8 ± 0.143 7) mg/L。敏感性频率分布显示，供试病原菌群体中已出现对多菌灵敏感性下降的亚群体，但其中仍有35.71%的菌株对多菌灵的敏感性频率呈正态分布，因此可将此部分菌株的平均EC₅₀值 (0.081 4 ± 0.028 9) mg/L作为拟轮枝镰孢对多菌灵的相对敏感基线。药剂驯化共获得6株抗性菌株，抗性倍数在5.05~12.22之间。抗性菌株的菌丝生长速率及菌丝干重均低于亲本菌株，表明其抗性菌株的生物适合度有所降低，同时发现其抗药性均不能稳定遗传。室内交互抗性测定结果表明，拟轮枝镰孢对多菌灵的抗性与咪鲜胺、戊唑醇、三唑酮及吡唑醚菌酯之间均不存在交互抗性关系。     

江西省番茄绵疫病菌对嘧菌酯的敏感性检测及抗性风险分析

为明确番茄绵疫病菌对嘧菌酯的敏感性，采用菌丝生长速率法测定了2018—2019年从江西省番茄主产区采集分离得到的58株绵疫病菌Phytophthora capsici对嘧菌酯的敏感性，并以敏感菌株YD5为亲本，通过紫外线诱导获得了4株抗性突变体，研究了突变体的生物学性状；进而采用菌丝生长速率法测定了敏感菌株YD5及其4个抗性突变体对烯酰吗啉和甲霜灵的EC₅₀值，分析嘧菌酯与烯酰吗啉和甲霜灵是否存在交互抗性。结果表明:嘧菌酯对绵疫病菌菌丝生长有较强的抑制作用，其对58个绵疫病菌的EC₅₀值介于0.1867~1.6239 μg/mL之间，平均EC₅₀值为 (0.8606±0.3318) μg/mL，58个菌株对嘧菌酯的敏感性频率分布呈正态分布，表明番茄绵疫病菌对嘧菌酯仍然较为敏感。通过紫外线诱导获得4个抗性突变体，突变体的抗药性能够稳定遗传，且在致病力与游动孢子萌发率方面与亲本菌株无显著差异，产孢量较亲本菌株显著下降。嘧菌酯与烯酰吗啉和甲霜灵之间均不存在交互抗药性。研究表明，番茄绵疫病菌对嘧菌酯具有中等抗性风险，一旦田间出现抗性菌株，应立即采取措施控制菌群的转移扩散。同时，需加强番茄绵疫病菌对嘧菌酯的田间抗性监测，在生产过程中轮用或混用不同作用机制的药剂，以避免或延缓抗药性的发展。     

山东省玉米纹枯病菌对噻呋酰胺的敏感性及其抗性突变体的生物学性状

为明确山东省玉米纹枯病菌对噻呋酰胺的敏感性及其抗药性风险,采用菌丝生长速率法分别测定了采自山东泰安、临沂、潍坊、莱芜、日照及青岛6个地区的102株玉米纹枯病菌对噻呋酰胺的敏感性。结果表明:其EC₅₀值分布范围为0.010～0.194 μg/mL,平均EC₅₀ 值为 (0.086 ± 0.004) μg/mL,且敏感性呈连续单峰曲线分布。通过紫外诱导与药剂驯化的方法各获得5株耐药性菌株 (TA3-X2、TA17-X6、LY8-3、QD14-Y7和WF6-A2) 和1株抗性突变体 (QD2-Y4),其抗性水平在6.46～20.08倍之间,突变频率分别为0.87%和0.52%。对抗性突变体生物学性状的研究表明,紫外诱导获得的5株耐药性菌株其耐药性不能稳定遗传,而经药剂驯化获得的1株抗性突变体QD2-Y4的抗药性可稳定遗传;耐药性菌株TA3-X2的菌丝生长速率高于亲本菌株,其余菌株与亲本菌株差异不明显;5株耐药性菌株和1株抗性突变体的菌丝干重和菌核干重均低于亲本菌株;TA3-X2、WF6-A2及QD2-Y4的致病力低于亲本菌株,TA17-X6、LY8-3及QD14-Y7的致病力与亲本菌株无明显差异。交互抗性测定表明,噻呋酰胺抗性突变体与戊唑醇、丙环唑、咯菌腈、井冈霉素、苯醚甲环唑和多菌灵之间均无交互抗性,与啶酰菌胺和氟唑菌苯胺之间则存在交互抗性。研究表明,山东省6个地区的玉米纹枯病菌对噻呋酰胺比较敏感,推测噻呋酰胺可作为防治玉米纹枯病的理想候选药剂。     

水稻稻瘟病菌对烯肟菌胺的抗性风险评估及抗性机制初探

 采用菌丝生长速率法测定了100株采自我国主要水稻产区的水稻稻瘟病菌对烯肟菌胺的敏感性, 结果表明, 其EC₅₀分布于0.011 1~0.295 6 μg·mL^-1, 平均EC₅₀=(0.078 6±0.056 1) μg·mL^-1。供试菌株对烯肟菌胺的敏感性分布呈单侧峰曲线, 未出现抗药性亚群体, 可将该曲线作为稻病瘟菌对烯肟菌胺的敏感性基线。通过室内药剂驯化获得了7株抗药突变体, 突变频率为1.11×10^-4, 其中2株高抗突变体NJ0811-I和A10的抗性水平大于1 000倍, 抗药性性状能稳定遗传, 致病力显著弱于其亲本菌株;5株低抗突变体抗性水平在2.05～4.55倍之间, 抗药稳定性差, 适合度与亲本无显著性差异。交互抗药性结果表明, 烯肟菌胺与嘧菌酯存在正交互抗药性, 与田间防治稻瘟病常用药剂稻瘟灵、异稻瘟净无交互抗药性。综合分析表明, 稻瘟病菌对烯肟菌胺可能存在低到中等抗性风险。进一步克隆了抗药突变体及其亲本的cytb基因, CYTB氨基酸序列比对结果表明, 2株高抗突变体均在143位由甘氨酸突变为丝氨酸(G143S), 建立了高抗菌株的AS-PCR分子检测方法;而5株低抗突变体cytb基因未发生点突变, 推测可能存在其他的抗性分子机制。     

嘧菌酯对河南省小麦茎基腐病菌的抑制活性及对病害的防治效果

主要由假禾谷镰孢Fusarium pseudograminearum引起的茎基腐病是小麦上的重要病害,对产量及质量都有严重影响,目前尚无登记应用在该病害防治上的化学药剂。本研究从河南省17个地市采集病害样本,分离纯化得到82株小麦茎基腐病菌菌株,包括76株假禾谷镰孢和6株禾谷镰孢。嘧菌酯抑制76株假禾谷镰孢孢子萌发的EC₅₀值为0.02~1.54 μg/mL,平均EC₅₀值为 (0.33 ± 0.29) μg/mL;经数据异常值检验,舍弃异常菌株LHWY-6及SQYC-6后,嘧菌酯对74株 (97.37%) 正常菌株的平均EC₅₀值(0.30 ± 0.24) μg/mL可作为假禾谷镰孢对嘧菌酯的敏感性基线;不同地市菌株间敏感性存在差异,同一地市菌株间对嘧菌酯的敏感性差异较大,许昌、焦作、洛阳和商丘4市的菌株间敏感性差异倍数均在20.00以上,南阳、三门峡和开封3地的菌株间差异倍数均在2.00以下,其他地市菌株间差异倍数在2.70~12.00之间;假禾谷镰孢孢子萌发对嘧菌酯与其对丙硫菌唑、多菌灵、咯菌腈、氰烯菌酯、吡唑醚菌酯和戊唑醇的敏感性相比,除吡唑醚菌酯外其余5种药剂的抑制作用均弱于嘧菌酯;嘧菌酯对6株禾谷镰孢的EC₅₀值在0.10~0.42 μg/mL之间,平均EC₅₀值为 (0.19 ± 0.12) μg/mL;嘧菌酯对两种镰孢菌丝生长的抑制活性均较弱,EC₅₀都在7 μg/mL以上。离体条件下,15%嘧菌酯悬浮种衣剂在260 g/(100 kg种子) 剂量下防效达63.64%;温室盆栽时,在220 g/(100 kg种子) 剂量下防效为55.24%。嘧菌酯对小麦茎基腐病菌孢子萌发有明显的抑制作用,且在离体和温室条件下对病害均有很好的防治效果,可作为备选药剂推广使用。     

江苏省葡萄炭疽病菌群体对4种杀菌剂的敏感性

为明确江苏省葡萄炭疽病菌Colletotrichum gloeosporioides群体对苯醚甲环唑、吡唑醚菌酯、咯菌腈和戊唑醇4种杀菌剂的敏感性和抗性水平,本研究采用菌丝生长速率法测定了来自江苏省7个地区的68株葡萄炭疽病菌对上述4种药剂的敏感性,建立敏感基线,并分析菌株抗性水平和抗性频率。结果表明：苯醚甲环唑、吡唑醚菌酯、咯菌腈和戊唑醇对供试68株葡萄炭疽病菌的EC₅₀范围分别为0.03～1.20、0.05～3.48、0.14～1.20 mg/L和0.50～12.30 mg/L;对苯醚甲环唑、吡唑醚菌酯和咯菌腈的敏感基线分别为(0.53±0.032)(1.00±0.15) mg/L和(0.38±0.024) mg/L。68株菌株对戊唑醇的EC₅₀平均值为3.61 mg/L,因敏感性频率分布不符合建立敏感性基线要求,故未建立敏感性基线。供试菌株对苯醚甲环唑均表现为敏感,对吡唑醚菌酯和咯菌腈呈现一定的低抗水平,抗性频率分别为4.41%和3.03%;对戊唑醇呈低抗和中抗水平,抗性频率分别为16.18%和5.88%。该研究为防控江苏省葡萄炭疽病提...     

河南省假禾谷镰刀菌对咯菌腈的敏感性

由假禾谷镰刀菌Fusarium pseudograminearum引起的小麦茎基腐病已成为重要的土传病害,并且影响小麦的品质和产量。为了明确中国河南省假禾谷镰刀菌对咯菌腈的敏感性,采用菌丝生长速率法测定了咯菌腈对2019年从河南省6个地市分离的105株假禾谷镰刀菌F. pseudograminearum 的敏感性,通过最小显著差异法(LSD)和SPSS聚类方法对测定结果进行了分析,并测定了假禾谷镰刀菌对多菌灵和戊唑醇的敏感性,分析了咯菌腈与这两种杀菌剂毒力的相关性。结果表明:咯菌腈对供试菌株的最低抑制浓度(MIC)为0.2400 μg/mL。敏感性频率分布图显示,EC₅₀值范围在0.0027~0.0470 μg/mL,敏感性差异达17.41倍;敏感性频率分布为连续单峰曲线,平均EC₅₀值为(0.0263 ± 0.0101) μg/mL,可作为假禾谷镰刀菌对咯菌腈的敏感性基线。方差分析结果显示,不同县市的小麦假禾谷镰刀菌对咯菌腈的敏感性差异较大,EC₅₀值变化范围为0.0150~0.0335 μg/mL,其中咯菌腈对郑州中牟的敏感性最低和最高菌株的EC₅₀值相差16.78倍。聚类分析结果显示,河南省小麦茎基腐病菌菌株对咯菌腈敏感性差异与菌株的地理来源无明显关联性。多菌灵和戊唑醇对病菌的平均EC₅₀值分别为 (0.7881 ± 0.3153) μg/mL和(0.0886 ± 0.1453) μg/mL。病菌对咯菌腈与其对多菌灵和戊唑醇的敏感性之间无明显相关性。温室防效结果显示,用咯菌腈悬浮种衣剂对小麦进行拌种处理,2020年 (咯菌腈有效成分为75.0 μg/g)对小麦茎基腐病的防治效果可达58.00%,2021年 (咯菌腈有效成分为50.0 μg/g)的防治效果可达到63.69%。本研究结果可为咯菌腈在小麦茎基腐病防治中的合理使用提供依据,为病原菌对药剂的敏感性监测提供参考。     

黄淮麦区假禾谷镰刀菌对3种杀菌剂敏感性测定

以假禾谷镰刀菌Fusarium pseudograminearum为主要病原菌引起的小麦茎基腐病已经成为黄淮麦区的主要小麦病害之一,对小麦生产安全带来严重威胁。为了解假禾谷镰刀菌对氰烯菌酯、戊唑醇和咯菌腈3种杀菌剂的敏感性,采用菌丝生长速率法对采自河南、河北、山东的108株假禾谷镰刀菌进行了室内毒力测定。试验结果表明：氰烯菌酯对假禾谷镰刀菌的EC₅₀为0.088～0.929μg/mL,EC₅₀均值为(0.471±0.181)μg/mL;敏感性分布为连续单峰曲线,经Shapiro-Wilk正态性检验符合正态分布(W=0.988,P=0.437>0.05),所以将所有菌株的EC₅₀平均值0.471μg/mL定为假禾谷镰刀菌对氰烯菌酯的敏感基线;戊唑醇对供试菌株的EC₅₀为0.015～0.961μg/mL,EC₅₀均值为(0.384±0.219)μg/mL,敏感性分布不符合连续单峰的正态分布;咯菌腈对供试菌株的EC₅₀为0.029～0.354μg/mL,E...     

禾谷镰孢菌对氰烯菌酯的敏感性基线及室内抗药性风险初步评估

 本文报道了禾谷镰孢菌(Fusarium graminearum)对氰烯菌酯(2-氰基-3-氨基-3-苯基丙烯酸乙酯,JS399-19)的敏感性基线及其抗药性风险。离体条件下氰烯菌酯对51个禾谷镰孢菌菌株的平均EC₅₀和MIC值分别为(0.153±0.050)μg/mL和小于4.0μg/mL;通过紫外线照射和药剂驯化的方法获得了14个禾谷镰孢菌对氰烯菌酯的抗药性突变体,紫外光诱变抗药性突变频率为1.67×10^-7。这些突变体的抗性水平可分为低、中、高3种类型,其EC₅₀分别为1.5~15.0μg/mL、15.1~75.0μg/mL和75.0μg/mL以上。与亲本菌株2021相比,抗药突变体间的菌丝生长量和产生子囊壳能力发生不同程度的增加或下降,而分生孢子繁殖量则显著下降。在无药培养基上菌丝体转代培养8次后,抗药水平保持不变,且与亲本菌株有相同的致病性。所测定的突变体在含1%葡萄糖的PDA上菌丝生长除UV-2021-4显著下降外,其余都表现生长速率比亲本显著增加。在含3%和4%葡萄糖的PDA上2021生长优于亲本菌株。氰烯菌酯与苯并咪唑类、麦角甾醇生物合成抑制剂类、甲氧基丙烯酸酯类、二硫代氨基甲酸盐类和取代芳烃类杀菌剂没有交互抗性。     

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。     

番茄灰霉病菌对咯菌腈的抗性诱变及抗药突变体的生物学特性

为评估番茄灰霉病菌Botrytis cinerea对咯菌腈的抗性风险,就室内经紫外照射获得抗药突变体的方法及抗性突变体的生物学性状进行了研究。结果表明:番茄灰霉病菌分生孢子的紫外照射亚致死时间为90~120 s;经亚致死时间紫外照射后,4个亲本菌株中有2个菌株共产生了6个抗咯菌腈的突变体,其EC50值是亲本菌株的310倍以上,抗性突变频率为3.13×10-7;经紫外照射诱变获得的所有抗性突变体在菌丝生长速率、产孢量、产菌核能力及其在番茄果实上的致病性方面均比其亲本菌株明显降低。相关分析显示,所得抗咯菌腈突变体对氟啶胺、啶菌唑、啶酰菌胺和嘧霉胺无交互抗性。表明番茄灰霉病菌对咯菌腈的抗药性风险较低。     

小麦纹枯病菌对噻呋酰胺的敏感性及抗药性突变体的主要生物学性状

采用菌丝生长速率法,分别测定了采自河北、山东和河南未使用过酰胺类药剂地区的166株小麦纹枯病菌Rhizotonia cerealis Van der Hoeven对噻呋酰胺的敏感性,并对小麦纹枯病菌抗噻呋酰胺突变体的诱导方法及突变体的主要生物学性状进行了研究。结果表明:噻呋酰胺对166株小麦纹枯病菌的平均EC50值为(0.072±0.022)μg/mL,菌株频率呈连续单峰曲线分布,未发现敏感性明显下降的亚群体,因此可将该EC50值作为小麦纹枯病菌对噻呋酰胺的敏感基线。通过紫外诱导加菌落角变的方法获得了5株抗噻呋酰胺突变体,其抗药性水平介于5.5~18.9倍之间;药剂驯化未能获得抗药性突变体。突变体在PSA平板上的生长速率与亲本菌株无显著性差异,但其菌丝干重、菌核形成数量和菌核干重均明显低于亲本菌株;除突变体HD7-7U对石新828的致病力未发生明显变化外,其他突变体对石新828和良星99的致病力均明显减弱;5株突变体的抗药性均不能稳定遗传;噻呋酰胺与戊唑醇、井冈霉素、咯菌腈、三唑酮、丙环唑和多菌灵之间无交互抗性关系。     

中国河南省小麦纹枯病菌对咯菌腈的敏感性

为明确河南省小麦纹枯病菌对咯菌腈的敏感性,采用菌丝生长速率法测定了咯菌腈对2013年从河南省15个地市分离的98株病菌的毒力。结果表明:咯菌腈对供试小麦纹枯病菌菌株的EC50值在0.009~0.079 μg/mL之间,平均EC50值为(0.025 ±0.012)μg/mL;98个菌株对咯菌腈的敏感性分布呈连续单峰曲线,未出现敏感性下降的亚群体,可将(0.025 ±0.012)μg/mL作为小麦纹枯病菌对咯菌腈的敏感性基线;方差分析(LSD法)及SPSS聚类结果均显示,同一地市内的菌株对咯菌腈的敏感性差异较大,EC50最大值和最小值之比在1.0~4.1之间,而不同地区菌株间对咯菌腈敏感性差异不明显,咯菌腈EC50平均值变化范围在0.015~0.060 μg/mL之间,后者是前者的4倍;小麦纹枯病菌对咯菌腈的敏感性与其对噻呋酰胺、苯醚甲环唑、井冈霉素、丙环唑及戊唑醇的敏感性之间无明显相关性。本研究结果可为河南省小麦纹枯病防控杀菌剂的合理使用提供理论依据。     

Characterization of genetic and biochemical mechanisms of fludioxonil and pyrimethanil resistance in field isolates of Penicillium digitatum

Genetic and biochemical mechanisms of fludioxonil and pyrimethanil resistance in isolates of Penicillium digitatum were evaluated and compared to those characterized in other fungi. Resistant isolates were naturally occurring in packinghouses and were not associated with crop losses. For the phenylpyrrole fludioxonil, EC50 values were 0.02 to 0.04 microg/ml for sensitive, 0.08 to 0.65 microg/ml for moderately resistant (MR), and > 40 microg/ml for highly resistant (HR) isolates. Two fludioxonil-sensitive isolates evaluated were also significantly more sensitive to the unrelated dicarboximide fungicide iprodione, that also disrupts osmotic regulation, than the MR and HR isolates. There was no consistent relationship, however, between the HR and MR isolates and their sensitivity to iprodione or osmotic stress. Although, two nucleotide substitutions were found in a sequence analysis of the N-terminal amino acid repeat region of the os-1-related histidine kinase gene among isolates of P. digitatum, these were not correlated with fludioxonil resistance. In mycelia not exposed to fludioxonil, the amount of phosphorylated OS-2-related protein (PdOS-2) was higher in fludioxonil-sensitive isolates and lowest in the HR isolate. An increase in PdOS-2 was observed for sensitive and resistant isolates after exposure to fludioxonil. In addition, glycerol content in untreated mycelia of the fludioxonil-sensitive isolate was significantly higher than in resistant isolates. After exposure to fludioxonil, glycerol concentrations significantly increased in the sensitive and MR isolates, but not in the HR isolate. Thus, our studies indicate that the mode of action of fludioxonil in P. digitatum is probably the mitogen-activated protein kinase pathway that stimulates glycerol synthesis in sensitive and MR isolates. The general suppression of this pathway in resistant isolates was supported by the fact that growth and sporulation of MR and HR isolates were significantly reduced from that of sensitive isolates. In studies on the mode of action of anilinopyrimidines (AP), EC50 values for mycelial growth of P. digitatum and the previously characterized Botrytis cinerea were determined for cyprodinil and pyrimethanil using a defined culture medium without and with the addition of selected amino acids and homocysteine. The addition of amino acids resulted in a reduced toxicity of the two AP fungicides in both fungi, but the effect of each additive was significantly lower for P. digitatum than for B. cinerea. This suggests that methionine biosynthesis is not the primary target site of APs in P. digitatum.     

马铃薯早疫病菌对咯菌腈的敏感基线及其对不同药剂的交互抗性

采用菌丝生长速率法测定了河北省马铃薯主产区的122株早疫病菌Alternaria alternata对咯菌腈的敏感性,并测定了紫外诱导的15个抗咯菌腈突变菌株及其3个敏感亲本菌株对咯菌腈、异菌脲、腐霉利、苯醚甲环唑、吡唑醚菌酯的敏感性。田间马铃薯早疫病菌群体对咯菌腈保持高度敏感,122株早疫病菌对咯菌腈的EC₅₀值在0.0025~0.0857 μg/mL之间,平均值为0.0404±0.0171 μg/mL,相差34.87倍,呈近似正态分布,可作为早疫病菌对咯菌腈的敏感基线。此外,咯菌腈与吡唑醚菌酯和苯醚甲环唑之间无交互抗性关系,而与异菌脲和腐霉利之间存在正交互抗性关系。在田间药效试验中,50%咯菌腈WP施药量为105、115 g/hm²时,对马铃薯早疫病防效达80%以上,显著高于常规药剂80%代森锰锌WP 1 350 g/hm²和25%丙环唑EC 37.5 g/hm²的防效。表明咯菌腈可作为吡唑醚菌酯和苯醚甲环唑的替代药剂用于马铃薯早疫病的防治。     

Characterization of fludioxonil-resistant and pyrimethanil-resistant phenotypes of Penicillium expansum from apple

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. expansum was exposed to UV radiation to generate fungicide-resistant mutants. Four fludioxonil highly-resistant mutants (EC(50) > 1,000 microg/ml) and four pyrimethanil-resistant mutants (EC(50) > 10 microg/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 was 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 became resistant to TBZ at 5 microg/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 P. expansum 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. expansum; 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.     

Multiple resistance of Botrytis cinerea from kiwifruit to SDHIs,QoIs and fungicides of other chemical groups

BACKGROUND: Botrytis cinerea Pers.: Fr. is a high‐risk pathogen for fungicide resistance development that has caused resistance problems on many crops throughout the world. This study investigated the fungicide sensitivity profile of isolates from kiwifruits originating from three Greek locations with different fungicide use histories. Sensitivity was measured by in vitro fungitoxicity tests on artificial nutrient media. RESULTS: Seventy‐six single‐spore isolates were tested for sensitivity to the SDHI fungicide boscalid, the QoI pyraclostrobin, the anilinopyrimidine cyprodinil, the hydroxyanilide fenhexamid, the phenylpyrrole fludioxonil, the dicarboxamide iprodione and the benzimidazole carbendazim. All isolates from Thessaloniki showed resistance to both boscalid and pyraclostrobin, while in the other two locations the fungal population was sensitive to these two fungicides. Sensitive isolates showed EC₅₀ values to boscalid and pyraclostrobin ranging from 0.9 to 5.2 and from 0.04 to 0.14 mg L^?1 respectively, while the resistant isolates showed EC₅₀ values higher than 50 mg L^?1 for boscalid and from 16 to > 50 mg L^?1 for pyraclostrobin. All QoI‐resistant isolates carried the G143A mutation in cytb. Sensitivity determinations to the remaining fungicides revealed in total eight resistance phenotypes. No isolates were resistant to the fungicides fenhexamid and fludioxonil. CONCLUSION: This is the first report of B. cinerea field isolates with resistance to both boscalid and pyraclostrobin, and it strongly suggests that there may be a major problem in controlling this important pathogen on kiwifruit. Copyright © 2010 Society of Chemical Industry