吉林省西瓜蔓枯病菌对咪鲜胺和苯醚甲环唑敏感基线的建立和抗性监测

为明确吉林省西瓜蔓枯病菌Stagonosporopsis citrulli对咪鲜胺和苯醚甲环唑的抗药性水平, 本试验采用菌丝生长速率法测定了151株西瓜蔓枯病菌对这两种药剂的敏感性及两种药剂对西瓜蔓枯病菌的MIC值, 并测定了吉林省7个西瓜主产区的375株菌株对这两种药剂的抗性水平。结果表明, 供试的151株菌株对这两种药剂的敏感性频率分布均呈连续的单峰曲线, 接近正态分布; 对咪鲜胺和苯醚甲环唑的敏感基线分别为(0.203 0±0.135 3) μg/mL和(0.675 9±0.394 2) μg/mL; 两种药剂的最低抑制浓度MIC分别为20 μg/mL和40 μg/mL。供试375株菌株对两种杀菌剂的抗性频率均为0。本研究结果为咪鲜胺和苯醚甲环唑的合理用药策略提供了科学依据, 为后续其抗性风险评估奠定了基础。     

6种杀菌剂防治辣椒炭疽病田间药效试验

为筛选出防治辣椒炭疽病的有效药剂,采用25%炭露EC等6种杀菌剂对辣椒炭疽病进行了田间小区和示范区药效试验.结果表明,在发病初期按常用量喷施药剂1次,防治效果达62.92%～70.91%.25%炭露EC 1800倍液在小区和示范区试验中,1次施药防治效果均可达70%以上.可作为防治辣椒炭疽病的药剂轮换使用.     

葡萄霜霉病药剂防治试验

采用载玻片萌发法和田间药剂保护与治疗试验,比较了14种药剂对葡萄霜霉病菌孢子囊萌发的抑制作用及田间的防治效果。结果表明66.8%霉多克可湿性粉剂800倍液、70%安泰生可湿性粉剂400倍液、78%科博可湿性粉剂1300倍液,不仅在室内对孢子囊的萌发表现出较好的抑制作用;而且在田间,无论是病前保护,或是病后治疗都表现出较好的防治效果,是供试药剂中表现比较突出的。波尔多液的保护作用仍比较明显,其他药剂也有一定防治作用。生产上应根据当地病情及经济有效和轮换使用的原则,合理选择使用。     

棕竹灰斑病病原菌生物学特性及化学防治研究

[目的]研究棕竹灰斑病菌[Pestalotiopsis palmarum（Cke.）Stey.]的生物学特性并对其杀菌剂进行筛选。[方法]采集具有典型症状的病害标本,根据柯赫氏法则分离病原物和病原菌纯化后进行病原菌鉴定及生物学特性测定。同时,测定了4种供试杀菌剂在3种不同浓度下对病原菌的抑菌作用。[结果]菌丝生长最适温度、pH、碳源、氮源分别为25℃、pH 6、葡萄糖、硝酸钾;黑暗条件有利于菌丝的生长,而光照条件则有利于孢子的产生。供试药剂中以70%甲基托布津和50%使百功防效最为明显,分别在2 000和500μg/m l时防效高达100%。[结论]为棕竹灰斑病的防治提供了理论依据。     

The drug transporter MgMfs1 can modulate sensitivity of field strains of the fungal wheat pathogen Mycosphaerella graminicola to the strobilurin fungicide trifloxystrobin

BACKGROUND: The major facilitator superfamily (MFS) drug transporter MgMfs1 of the wheat pathogen Mycosphaerella graminicola (Fuckel) J Schroeter is a potent multidrug transporter with high capacity to transport strobilurin fungicides in vitro. The data presented in this paper indicate that, in addition to the predominant cause of strobilurin resistance, cytochrome b G143A subsititution, MgMfs1 can play a role in sensitivity of field strains of this pathogen to trifloxystrobin. RESULTS: In a major part of field strains of M. graminicola (collected in the Netherlands in 2004) containing the cytochrome b G143A substitution, the basal level of expression of MgMfs1 was elevated as compared with sensitive strains lacking the G143A substitution. Induction of MgMfs1 expression in wild-type isolates upon treatment with trifloxystrobin at sublethal concentrations proceeded rapidly. Furthermore, in disease control experiments on wheat seedlings, disruption mutants of MgMfs1 displayed an increased sensitivity to trifloxystrobin. CONCLUSION: It is concluded that the drug transporter MgMfs1 is a determinant of strobilurin sensitivity of field strains of M. graminicola.     

Resistance to pyraclostrobin, boscalid and multiple resistance to Pristine® (pyraclostrobin + boscalid) fungicide in Alternaria alternata causing alternaria late blight of pistachios in California

Pristine® (pyraclostrobin + boscalid) is a fungicide registered for the control of alternaria late blight in pistachio. A total of 95 isolates of Alternaria alternata collected from orchards with and without a prior history of Pristine® sprays were tested for their sensitivity towards pyraclostrobin, boscalid and Pristine® in conidial germination assays. The EC₅₀ values for 35 isolates from orchards without Pristine® sprays ranged from 0·09 to 3·14 µg mL^?1 and < 0·01 to 2·04 µg mL^?1 for boscalid and Pristine®, respectively. For pyraclostrobin, 27 isolates had EC₅₀ < 0·01 µg mL^?1 and six had low resistance (mean EC₅₀ value = 4·71 µg mL^?1). Only one isolate was resistant to all three fungicides tested, with EC₅₀ > 100 µg mL^?1. Among 59 isolates from the orchard with a history of Pristine® sprays, 56 were resistant to pyraclostrobin; only two were sensitive (EC₅₀ < 0·01 µg mL^?1) and one was weakly resistant (EC₅₀ = 10 µg mL^?1). For the majority of these isolates EC₅₀ values ranged from 0·06 to 4·22 µg mL^?1 for boscalid and from 0·22 to 7·74 µg mL^?1 for Pristine®. However, seven isolates resistant to pyraclostrobin were also highly resistant to boscalid and Pristine® and remained pathogenic on pistachio treated with Pristine®. Whereas strobilurin resistance is a common occurrence in Alternaria of pistachio, this is the first report of resistance to boscalid in field isolates of phytopathogenic fungi. No cross resistance between pyraclostrobin and boscalid was detected, suggesting that Pristine® resistance appears as a case of multiple resistance.     

Mefenoxam sensitivity and fitness analysis of Phytophthora nicotianae isolates from nurseries in Virginia, USA

Mefenoxam is one of the most commonly used fungicides for managing diseases caused by Phytophthora spp. on ornamentals. The objectives of this study were to determine whether Phytophthora nicotianae, a destructive pathogen of numerous herbaceous annual and perennial plant species in nurseries, has developed resistance to mefenoxam, and to evaluate the fitness of mefenoxam‐resistant isolates. Ninety‐five isolates of P. nicotianae were screened for sensitivity to mefenoxam on 20% clarified V8 agar at 100 a.i. µg mL^?1. Twenty‐five isolates were highly resistant to this compound with EC₅₀ values ranging from 235·2 to 466·3 µg mL^?1 and four were intermediately resistant with EC₅₀ values ranging from 1·6 to 2·9 µg mL^?1. Sixty‐six isolates were sensitive with EC₅₀ values less than 0·04 µg mL^?1. Nine resistant and seven sensitive isolates were tested for mefenoxam sensitivity on Pelargonium × hortorum cv. White Orbit. Mefenoxam provided good protection of pelargonium seedlings from colonization by sensitive isolates, but not by any resistant isolates. Four resistant and four sensitive isolates were compared for fitness components and their relative competitive ability on Lupinus Russell Hybrids in the absence of mefenoxam. Resistant isolates outcompeted sensitive ones within 3 to 6 sporulation cycles on lupin seedlings, regardless of their initial proportions in mixed zoospore inoculum. Resistant isolates exhibited greater infection rate and higher sporulation ability than sensitive ones when they were applied separately onto lupins. These results suggest that fungicide resistance may pose a serious challenge to the continued effectiveness of mefenoxam as a control option for nursery growers.     

Selection for decreased sensitivity to phosphite in Phytophthora cinnamomi with prolonged use of fungicide

To test the hypothesis that resistance in Phytophthora cinnamomi to control by the fungicide phosphite (phosphonate) would arise in sites with prolonged use of phosphite, 30 P. cinnamomi isolates were collected from a range of sites with different phosphite‐use histories, including phosphite‐treated and untreated avocado orchards, and phosphite‐treated and untreated native vegetation sites. The colonizing ability of these isolates was tested by different inoculation methods against a range of host tissues, treated and untreated with phosphite, including mycelial stem inoculation on clonally propagated Leucadendron sp., mycelial root inoculation of lupin seedlings and zoospore inoculation of Eucalyptus sieberi cotyledons. Isolates from avocado orchards with a long history of phosphite use were, on average, more extensive colonizers of the phosphite‐treated Leucadendron sp., lupin seedling roots and Eucalyptus sieberi cotyledons. These isolates did not colonize untreated plant tissue (Leucadendron sp.) more extensively than isolates from sites with no history of phosphite use and no isolates were resistant to control by phosphite. Analysis of all isolates with microsatellite markers revealed the majority were from a single clonal lineage. Selection for decreased sensitivity to phosphite in planta has taken place within asexual clonal lineages of P. cinnamomi in sites with prolonged use of phosphite.     

辽宁省蔬菜灰霉病菌对嘧霉胺的抗药性

2006年从辽宁省不同地区采集蔬菜灰霉病果或病叶,经分离共获得灰霉病菌株86株。采用菌丝生长速率法测定了其对嘧霉胺的敏感性。试验结果表明,灰霉病菌对嘧霉胺产生中等水平抗药性,抗性频率为17.41%。经紫外、药剂联合诱导获得了高抗菌株,抗性倍数最高达62.78倍。嘧霉胺与多菌灵和腐霉利间不存在交互抗药性,苯胺基嘧啶类杀菌剂之间存在交互抗性。野生抗性菌株具有较好的遗传稳定性,连续转接9次后抗药性无明显下降。不同菌株的菌丝生长速度、鲜重和产孢量存在明显差异,但该差异与灰霉病菌对嘧霉胺的敏感性无相关性。     

2007年我国部分麦区小麦白粉菌对三唑酮的抗药性监测

采用拌种离体叶段法测定了我国9个省（市）的112个小麦白粉菌株对三唑酮的抗性。结果表明,供试菌株的平均EC50为57.25mg/L,平均抗性水平为27.39倍,其中86.61%供试菌株已经产生抗性,抗药性比敏感菌株高出10~40倍的菌株占47.32%,四川、山东、甘肃和贵州等地菌株的抗性高于其他地区。此结果可为三唑类杀菌剂在我国的推广应用和制定合理的抗药性治理措施提供依据。