The susceptibility of the Indian field mouse,Mus booduga gray,to anticoagulant rodenticidal baits

The baseline susceptibility of the Indian field mouse, Mus booduga was established for warfarin, bromadiolone and brodifacoum by means of nochoice feeding tests. The mice were found to be more susceptible to the second generation anticoagulants bromadiolone (0.005 g kg^?1) and brodifacoum (0.002 g kg^?1) than warfarin (0-25 g kg^?1). They required 8–10 days feeding on warfarin (0.25 g kg^?1) diet for complete mortality. A feeding period of 8 days corresponding to 99% mortality was suggested as a checking test for registering future warfarin resistance in suspect samples of M. booduga.     

Rodent tissue residue and secondary hazard studies with bromadiolone1

A series of toxicological, residue, secondary hazard, and environmental fate studies were completed with bromadiolone. The compound was eliminated rapidly after ingestion by Rattus norvegicus and Mus domesticus. In R. norvegicus, 75% of the bromadiolone was eliminated within 4 days. Dead rodents collected from field trials using bromadiolone had residue levels of 1.92 in R. rattus, 1.17 in M. domesticus, and 0.49 ppm in Spermophilus beecheyi. The LD50 for bromadiolone in beagle dogs was calculated at 8.1 mg kg^-1 (10.7 for males and 6.3 mg kg^-1 in females). The approximate LD50 in Canis latrans was 10 mg kg^-1. Dietary LC50 determination compound in Putorius putorius furo was 9.8 ppm. Secondary hazard studies showed the rodenticide to have little potential to snakes and birds of prey if used properly. Field tests with grain and pelleted baits over 21 days demonstrated that the active ingredient degraded by 78 and 45%, respectively.     

Bromadiolone susceptibility in wild and laboratory Mus musculus L.(house mice) in Buenos Aires,Argentina

BACKGROUND: Rodents are major pests in many agricultural systems, where they can cause significant economic losses and involve a sanitary risk. The application of anticoagulant rodenticides for rodent control has showed a decrease in effectiveness through time because of the development of resistant populations and the development of aversion behaviour. The goal of the present study was to test the susceptibility to bromadiolone and the existence of anticoagulant resistance in Mus musculus L. (house mouse) in Argentina. We conducted a feeding test with wild animals captured in poultry farms and a laboratory strain that were fed with bromadiolone bait. RESULTS: Three animals of the field experimental group survived the 21 days study period, while for laboratory animals mortality was 100%. Control field animals which were fed without anticoagulant showed 100% survival. CONCLUSION: We found evidence of the presence of anticoagulant resistant M. musculus L. in the study area. Feeding behaviour may have contributed to increasing the time of survival, and may be a mechanism that allows metabolic clearance of the bromadiolone. Under field conditions control with anticoagulants would be less effective because animals have alternative food. Copyright © 2009 Society of Chemical Industry     

Identification of cytochrome P450 differentiated expression related to developmental stages in bromadiolone resistance in rats (Rattus norvegicus)

Adult, 20-week-old, rats from a Danish bromadiolone-resistant strain of rats (Rattus norvegicus) over-express the cytochrome P450 genes Cyp2e1, Cyp3a2 and Cyp3a3 upon bromadiolone exposure. Furthermore, adult female rats of this strain over-express the Cyp2c13 gene and suppress Cyp2c12, while males over-express the Cyp2a1 gene. The altered gene expression has been suggested to be involved in the bromadiolone resistance by facilitating enhanced anticoagulant metabolism. To investigate the gene expression of these cytochrome P450 genes in rats of different developmental stages we compared expression profiles from 8-, 12- and 20-week-old resistant rats of the Danish strain to profiles of anticoagulant-susceptible rats of same ages. The three age-groups were selected to represent a group of pre-pubertal, pubertal and adult rats. We found expression profiles of the pre-pubertal and pubertal resistant rats to concur with profiles of the adults suggesting that cytochrome P450 enzymes are involved in the Danish bromadiolone resistance regardless of developmental stage. We also investigated the relative importance of the six cytochrome P450s in the different development stages of the resistant rats. The P450-3a2 and -3a3 isoforms were proposed to be of higher importance in adult male resistance than in pre-pubertal resistance. In contrast, the P450-2c13 and -3a2 isoforms were proposed to be more important in sexual immature female resistance, while the P450-2e1 and -3a3 isoforms were suggested to play a more significant role in adult female resistance.     

Resistance tests and field trials with bromadiolone for the control of Norway rats (Rattus norvegicus) on farms in Westphalia, Germany

BACKGROUND: The aim of this study was to determine the incidence and the level of resistance to bromadiolone among rats on farms suspected of being foci of resistance by using the international normalised ratio (INR)‐based blood clotting response (BCR) test. Whether the level of reduced susceptibility constitutes ‘practical resistance’ was subsequently determined in field trials. RESULTS: The 2.5 multiple of the ED₅₀ baseline was used to test for the incidence of resistance, and higher multiples in the range of the suspected resistance factor were used to investigate the degree of resistance. The ED₅₀ values of bromadiolone in resistant rats were confirmed in the range 4.70–7.05 mg kg^?1 for males and 4.62–6.61 mg kg^?1 for females. Variations within these ranges appeared between farms. According to the BCR resistance tests, 50–100% of rats were classified as resistant prior to the field trials; 29–100% of rats survived the treatments. CONCLUSION: BCR tests based on the use of the INR and baselines are suitable for determining the incidence and for assessing the level of resistance in populations of Norway rats. The majority of rats of the Westphalian resistant strain, characterised by the Y139C marker in VKOR, are resistant to bromadiolone under practical control conditions. Copyright © 2011 Society of Chemical Industry     

稻稗HJHL-715种群对五氟磺草胺的抗药性水平及抗性机理分析

为明确东北稻区稻稗Echinochloa oryzoides HJHL-715种群对五氟磺草胺的抗性水平及抗性机制,采用整株生物测定法测定稻稗种群对五氟磺草胺的敏感性,明确抗性种群的交互抗性和多抗性情况,研究3种细胞色素P450抑制剂对其敏感性的影响;并应用分子生物学方法进行稻稗的乙酰乳酸合酶(acetolactate synthase,ALS)离体活性测定、ALS基因序列分析及其表达量测定。结果表明:在东北稻区,五氟磺草胺对稻稗HJHL-715种群鲜重的抑制中剂量GR50为62.53 g/hm^2;稻稗HJHL-715的ALS基因序列中未发现氨基酸突变,其ALS离体活性与敏感种群的ALS离体活性无显著性差异,ALS基因表达量显著低于敏感种群。1-氨基苯并三唑(1-aminobenzotriazole,ABT)、胡椒基丁醚(piperomyl butoxide,PBO)、马拉硫磷3种P450抑制剂显著提高了稻稗HJHL-715种群对五氟磺草胺的敏感性,使其对五氟磺草胺的GR50由原来的62.53 g/hm^2分别下降到5.78、5.02、3.53 g/hm^2。表明东北稻区已经出现了对五氟磺草胺具有高水平抗性的稻稗种群,稻稗HJHL-715种群对五氟磺草胺的抗性很可能是由细胞色素P450介导的代谢增强所致。     

Involvement of hepatic xenobiotic related genes in bromadiolone resistance in wild Norway rats, Rattus norvegicus (Berk.)

To examine the role of xenobiotic relevant genes in bromadiolone resistance in wild Norway rats (Rattus norvegicus) we compared the constitutive liver gene expression and expression upon bromadiolone administration in bromadiolone resistant and anticoagulant susceptible female rats using a LNA microarray and quantitative PCR. Resistant rats showed significantly higher constitutive expression of the cytochrome P450 genes Cyp2c13 and Cyp3a2 and lower expression of Cyp2e1 and Gpox1 compared to the susceptible rats. The Cyp1a2, Cyp2c13, Cyp2e1, Cyp3a2 and Cyp3a3 genes were significantly higher expressed in resistant than susceptible rats upon bromadiolone exposure. To establish how bromadiolone affected xenobiotic gene expression in the two strains we compared bromadiolone expression profiles to saline profiles of both strains. Bromadiolone mediated significant up-regulation of Cyp2e1 and Cyp3a3 expression in the resistant rats whereas the rodenticide conferred down-regulation of Cyp2e1, Cyp3a3 and Gpox1 and induction of Cyp2c12 expression in susceptible rats. Cyp2c13 and Cyp3a2 expression were markedly suppressed in both strains upon treatment. This suggests that xenobiotic relevant enzymes play a role in bromadiolone resistance in the Norway rat. A high constitutive expression of Cyp2c13 and Cyp3a2 and induction of Cyp1a2, Cyp2e1 and Cyp3a3 expression during bromadiolone exposure may increase the resistance to bromadiolone presumably by facilitating increased detoxification and decreased liver injury.     

Pi34-AVRPi34: a new gene-for-gene interaction for partial resistance in rice to blast caused by Magnaporthe grisea

The japonica rice (Oryza sativa) cultivar Chubu 32 has a high level of partial resistance to blast, which is mainly controlled by a dominant resistance gene located on chromosome 11. The partial resistance to the rice blast fungus (Magnaporthe grisea) in Chubu 32 has isolate specificity; isolate IBOS8-1-1 is more aggressive on Chubu 32 than are other isolates. We hypothesized that the gene-for-gene relationship fits this case of a partial resistance gene in Chubu 32 against the avirulence gene in the pathogen. The partial resistance gene in Chubu 32 was mapped between DNA markers C1172 (and three other co-segregated markers) and E2021 and was designated Pi34. In the 32 F₃ lines from the cross between a chromosome segment substitution line (Pi34⁻) from Koshihikari/Kasalath and Chubu 32, the lines with high levels of partial resistance to the M. grisea isolate Y93-245c-2 corresponded to the presence of Pi34 estimated by graphic genotyping. This indicated that Pi34 has partial resistance to isolate Y93-245c-2 in compatible interactions. The 69 blast isolates from the F₁ progeny produced by the cross between Y93-245c-2 and IBOS8-1-1 were tested for aggressiveness on Chubu 32 and rice cultivar Koshihikari (Pi34⁻). The progeny segregated at a 1 : 1 ratio for strong to weak aggressiveness on Chubu 32. The results suggested that Y93-245c-2 has one gene encoding avirulence to Pi34 (AVRPi34), and IBOS8-1-1 is extremely aggressive on Chubu 32 because of the absence of AVRPi34. This is the first report of a gene-for-gene relationship between a fungal disease resistance gene associated with severity of disease and pathogen aggressiveness.     

A molecular mechanism of resistance to streptomycin in <Emphasis Type="Italic">Xanthomonas oryzae</Emphasis> pv. <Emphasis Type="Italic">oryzicola</Emphasis>

Xanthomonas oryzae pv. oryzicola, the causal agent of rice leaf streak disease, was found to be sensitive to streptomycin (an aminocyclitol glycoside antibiotic), by inhibition of protein synthesis resulting from interference with translational proofreading. This study aimed to determine the molecular resistance mechanism of X. oryzae pv. oryzicola to streptomycin. Seven streptomycin-resistant mutants were obtained by UV induction or streptomycin selection. These mutants can grow at 100 μg ml⁻¹ of streptomycin while the wild-type strain (RS105) cannot grow at 5 μg ml⁻¹. Sequencing indicated that the rpsL gene encoding ribosomal protein S12 has 375 bp encoding 125 amino acid residues. In all resistant strains, a mutation in which AAG was substituted for AGG (Lys→Arg) occurred either at codon 43 or 88. Two plasmids, pUFRRS and pUFRRX, were constructed by ligating the rpsL gene into the cosmid pUFR034. The plasmids pUFRRS and pUFRRX containing the Lys→Arg mutation of the rpsL gene conferred streptomycin resistance to the sensitive wild-type strain by electroporation. Both transformants, RS1 and RS2, could grow in the medium containing 50 μg ml⁻¹ of streptomycin. A mutation at codon 43 or 88 in rpsL can result in resistance of Xanthomonas oryzae pv. oryzicola to streptomycin.     

Inheritance of resistance to a new non‐steroidal ecdysone agonist,fufenozide, in the diamondback moth,Plutella xylostella (Lepidoptera: Plutellidae)

BACKGROUND: The diamondback moth (DBM), Plutella xylostella (L.), is a cosmopolitan pest of cruciferous crops. Fufenozide, a novel non‐steroidal ecdysone agonist, exhibits good efficacy and plays an increasingly important role in the control of Lepidopterous pests in China. A laboratory strain of DBM was selected for resistance to fufenozide, and the genetic basis of resistance was studied. RESULTS: The resistant strain, selected under laboratory conditions, exhibited a higher level of resistance to fufenozide (302.8‐fold based on LC₅₀s) than the laboratory susceptible strain. Mortality data from the testing of F₁ progeny of reciprocal crosses of resistant and susceptible DBM indicated that resistance was autosomal and incompletely recessive with a degree of dominance of ?0.664. Chi‐square analysis from responses of a backcross of crossed F₁ progeny and the resistant strain and F₂ progeny were highly significant, suggesting that the resistance was probably controlled by more than one gene. The estimated realised heritability (h²) of fufenozide resistance was 0.08, indicating that diamondback moth may have a lower chance of developing resistance to fufenozide than other kinds of insecticide. CONCLUSION: The resistance of DBM to fufenozide might be autosomal and incompletely recessive, and the resistance is probably controlled by more than one gene. These results provide the basic information for pest management programmes. Copyright © 2009 Society of Chemical Industry     

Methods to control the two forms of Arvicola terrestris in orchards in the Federal Republic of Germany1

Different methods had to be developed in the Federal Republic of Germany (FRG) for the control of the fossorial and the aquatic form of Arvicola terrestris. The fossorial form could be controlled on small areas by trapping but, on large areas where this is not feasible, satisfactory results were obtained by fumigation with carbon monoxide or carbon dioxide. The latter was judged superior as it does not endanger man and proved relatively humane. Sound-emitting devices that were tested against fossorial A. terrestris showed no effect at all. To control the aquatic form, a floating poison-bait station was developed. It was tested with baits containing bromadiolone, chlorophacinone or calciferol during 2 years on an area of 300 ha. Best results were achieved with fresh carrots soaked with chlorophacinone. Careful checks of the area under investigation did not reveal any evidence of secondary poisoning of non-target species.     

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。     

Quantitative trait loci associated with resistance to a potato isolate of Verticillium albo‐atrum in Medicago truncatula

Verticillium albo‐atrum is responsible for considerable yield losses in many economically important crops, among them alfalfa (Medicago sativa). Using Medicago truncatula as a model for studying resistance and susceptibility to V. albo‐atrum, previous work has identified genetic variability and major resistance quantitative trait loci (QTLs) to Verticillium. In order to study the genetic control of resistance to a non‐legume isolate of this pathogen, a population of recombinant inbred lines (RILs) from a cross between resistant line F83005.5 and susceptible line A17 was inoculated with a potato isolate of V. albo‐atrum, LPP0323. High genetic variability and transgressive segregation for resistance to LPP0323 were observed among RILs. Heritabilites were found to be 0·63 for area under the disease progress curve (AUDPC) and 0·93 for maximum symptom score (MSS). A set of four QTLs associated with resistance towards LPP0323 was detected for the parameters MSS and AUDPC. The phenotypic variance explained by each QTL (R²) was moderate, ranging from 4 to 21%. Additive gene effects showed that favourable alleles for resistance all came from the resistant parent. The four QTLs are distinct from those described for an alfalfa V. albo‐atrum isolate, confirming the existence of several resistance mechanisms in this species. None of the QTLs co‐localized with regions involved in resistance against other pathogens in M. truncatula.     

Insecticide resistance management of Bemisia tabaci (Hemiptera: Aleyrodidae) in Australian cotton – pyriproxyfen,spirotetramat and buprofezin

BACKGROUND

Bemisia tabaci is a globally significant agricultural pest including in Australia, where it exhibits resistance to numerous insecticides. With a recent label change, buprofezin (group 16), is now used for whitefly management in Australia. This study investigated resistance to pyriproxyfen (group 7C), spirotetramat (group 23) and buprofezin using bioassays and available molecular markers.

RESULTS

Bioassay and selection testing of B. tabaci populations detected resistance to pyriproxyfen with resistance ratios ranging from 4.1 to 56. Resistance to spirotetramat was detected using bioassay, selection testing and sequencing techniques. In populations collected from cotton, the A2083V mutation was detected in three populations of 85 tested, at frequencies ≤4.1%, whereas in limited surveillance of populations from an intensive horticultural region the frequency was ≥75.8%. The baseline susceptibility of B. tabaci to buprofezin was determined from populations tested from 2019 to 2020, in which LC₅₀ values ranged from 0.61 to 10.75 mg L⁻¹. From the bioassay data, a discriminating dose of 200 mg L⁻¹ was developed. Recent surveillance of 16 populations detected no evidence of resistance with 100% mortality recorded at doses ≤32 mg L⁻¹. A cross-resistance study found no conclusive evidence of resistance to buprofezin in populations with high resistance to pyriproxyfen or spirotetramat.

CONCLUSIONS

In Australian cotton, B. tabaci pest management is challenged by ongoing resistance to pyriproxyfen, while resistance to spirotetramat is an emerging issue. The addition of buprofezin provides a new mode-of-action for whitefly pest management, which will strengthen the existing insecticide resistance management strategy. © 2023 Commonwealth of Australia. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

The glutamate dehydrogenase gene gdhA increased the resistance of tobacco to glufosinate

The gene gdhA from Escherichia coli, that encodes a NADPH‐dependent glutamate dehydrogenase (GDH), directs a novel pathway in transgenic plants that allows an increase in ammonium assimilation. Glufosinate leads to plant death by the irreversible inhibition of glutamate synthetase (GS) leading to a disruption of subsequent GS‐related processes resulting in elevated ammonium and disruption of photorespiration. Therefore, it was speculated that the gdhA‐transformed plants may exhibit a novel mechanism of resistance to glufosinate by altered activity of the GDH‐directed pathway(s) and subsequently related processes. Studies were conducted in the greenhouse to evaluate the resistance of tobacco plants containing the gdhA gene to glufosinate. Five tobacco genotype lines were investigated including a non‐transformed control line, a positive control line and three transformed lines with levels of increasing GDH activity directed by the gdhA gene. Plants transformed with the gdhA gene expressed up to six times increased level of resistance (GR₅₀) to glufosinate compared with the non‐transformed control, which is 100 times less resistant than plants transformed with the bar gene. The GDH activity among lines was highly correlated (r² = 0.9903) with the level of herbicide resistance. Thus, the use of the E. coli gdhA gene in plant transformations can provide an additional mechanism for resistance to glufosinate.     

Resistance assessment of grapevine leaves to downy mildew with sporulation area scoring

The use of resistant individuals obtained through a breeding program, aimed at decreasing chemical treatments, is one of the most promising strategies for control of downy mildew caused by Plasmopara viticola in grapevine. In this study, 869 hybrid grape individuals, obtained by crossing the resistant Regent grape cultivar with sensitive Alphonse Lavallée, were tested after artificial inoculation of detached leaves by drops of the pathogen inoculum. Sporulation severity, as visual evaluation of sporulation density including necrosis, and sporulation incidence were scored to assess resistance level, then the sporulation area (mm²) was measured for each individual. The criterium of sporulation incidence could not describe all resistance levels. Sporulation area made it possible to measure the entire area in detail for how the pathogen spread at the inoculation site. Sporulation area was not fully consistent with sporulation severity. In this context, a new scale for sporulation area was developed to determine resistance level to the pathogen by taking into account the distribution of sporulation area values within those obtained from sporulation severity scales. Six categories ranging from 0 to 0.05 mm² (extremely resistant-ER) to ≥15.1 mm² (extremely sensitive-ES) were defined. 43 of the 869 individuals tested through the three evaluation criteria, in which no sporulation was observed, and 18 additional individuals with sporulation area of <0.05 mm² were scored in the ER group. Microscopic analysis confirmed findings for the ER group and other resistance levels. The authors suggest that the scale of sporulation area will be useful for assessment of resistance to downy mildew on grapevine leaves.

     

Evaluation Of Tests to Determine Resistance of Zantedeschia spp. (Araceae) to Soft Rot caused by Erwinia carotovora subsp. carotovora

Bacterial soft rot caused by Erwinia carotovora subsp. carotovora is a major disease in Zantedeschia spp., particularly in cultivars from the section Aestivae. The disease can be partly controlled by cultural measures, but by combining cultural methods with resistant plant material a promising strategy for control of soft rot can be developed. No tests are available for resistance testing in breeding Zantedeschia spp. Therefore, three tests developed for use in potato breeding were adapted for use on eight cultivars of Zantedeschia spp. Variation was found in all three tests. Resistant control cultivar Zantedeschia aethiopica Crowborough scored most resistant in all three tests. Within the section Aestivae, degrees of susceptibility were identified that were in agreement with each other and with field observations, indicating reliability of two of the methods in which tubers were used. The correlation coefficient of these two tests was high. A new non-destructive test method was developed for use on seedlings which involved immersion of leaf disks in a bacterial suspension. The percentage of decayed leaf area was a measure of resistance and results were in general agreement with the other tests. These methods will be useful for breeding for soft rot resistance and performing genetic analyses.     

Genetic control of resistance to tridemorph inustilago maydis

Mutants ofUstilago maydis with low resistance to tridemorph isolated in a mutation frequency of 7x 10^-6 after UV-irradiation and selection on media containing 25 μg ml^-1 tridemorph. Genetic analysis with nine such mutant isolates resulted in the identification of two unlinked chromosomal loci,U/tdm- 1 andU/tdm- 2. TheU/tdm mutations are responsible for low resistance levels to tridemorph (resistance factor, Rf, of 3 or 5 based on effective concentration causing a 50% reduction in the growth rate (EC₅₀) or minimal inhibitory concentration (MIC) values, respectively) and low to moderate level of resistance to fenpropimorph (Rf 10 or 16 based on MIC or EC₅₀, respectively) and fenpropidin (Rf 5 or 11 based on MIC or EC₅₀, respectively). Haploid strains carrying bothU/tdm mutations exhibit higher levels of resistance to the above fungicides, indicating interallelic interaction between nonallelic genes. Crosses between mutants carrying theU/tdm- genes with compatible isolates carrying theU/fpm- 1 orU/fpm- 2 mutations, which were found in previous work to carry fenpropimorph resistance, yielded in all cases a large number of recombinants with wild-type sensitivity, indicating that the mutant genes involved were not allelic. Cross-resistance studies with the inhibitors of C-14 demethylase showed that. the U/tdm-mutations were responsible for increased sensitivity to the triazoles triadimefon, triadimenol, propiconazole and flusilazole, and to the pyridine pyrifenox. Study of gene effect on the fitness ofU. maydis showed thatU/tdm-mutations appeared to be pleiotropic, having more or less adverse effects on growth rate in liquid culture and pathogenicity on young corn plants.     

Genetic analysis and molecular characterisation of laboratory and field mutants of Botryotinia fuckeliana (Botrytis cinerea) resistant to QoI fungicides

BACKGROUND: QoI fungicides, inhibitors of mitochondrial respiration, are considered to be at high risk of resistance development. In several phytopathogenic fungi, resistance is caused by mutations (most frequently G143A) in the mitochondrial cytochrome b (cytb) gene. The genetic and molecular basis of QoI resistance were investigated in laboratory and field mutants of Botryotinia fuckeliana (de Bary) Whetz. exhibiting in vitro reduced sensitivity to trifloxystrobin. RESULTS: B. fuckeliana mutants highly resistant to trifloxystrobin were obtained in the laboratory by spontaneous mutations in wild‐type strains, or from naturally infected plants on a medium amended with 1–3 mg L^?1 trifloxystrobin and 2 mM salicylhydroxamic acid, an inhibitor of alternative oxidase. No point mutations were detected, either in the complete nucleotide sequences of the cytb gene or in those of the aox and Rieske protein genes of laboratory mutants, whereas all field mutants carried the G143A mutation in the mitochondrial cytb gene. QoI resistance was always maternally inherited in ascospore progeny of sexual crosses of field mutants with sensitive reference strains. CONCLUSIONS: The G143A mutation in cytb gene is confirmed to be responsible for field resistance to QoIs in B. fuckeliana. Maternal inheritance of resistance to QoIs in progeny of sexual crosses confirmed that it is caused by extranuclear genetic determinants. In laboratory mutants the heteroplasmic state of mutated mitochondria could likely hamper the G143A detection, otherwise other gene(s) underlying different mechanisms of resistance could be involved. Copyright © 2012 Society of Chemical Industry