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Fungicide Resistance (fungicide + resistance)
Selected AbstractsVariation of Fungicide Resistance in Czech Populations of Pseudoperonospora cubensisJOURNAL OF PHYTOPATHOLOGY, Issue 3 2007J. Urban Abstract During the growing seasons between the years 2001 and 2004, 98 isolates of Pseudoperonospora cubensis from nine regions of Czech Republic were collected and screened for tolerance/resistance to the three frequently used fungicides (propamocarb, fosetyl-Al, metalaxyl). Fungicides were tested in five different concentrations, using a floating disc bioassay. Fungicide effectiveness varied considerably. Propamocarb appeared most effective and all the isolates collected in the years 2001,2003 were found sensitive to all tested concentrations [607,9712 ,g active ingredient (a.i.)/ml]. In 2004, some strains with increased resistance to propamocarb were detected. These strains were characterized by tolerance at the lowest concentrations (607 ,g a.i./ml, eventually on 1214 ,g a.i./ml); however, they were controlled by 2428 ,g a.i./ml. Fosetyl-Al was effective at the recommended concentration of 1600 ,g a.i./ml against all isolates. However, the occurrence of isolates (collected in 2001) which sporulated at low concentrations (400 and 800 ,g a.i./ml) indicated that the selection for tolerance occurs in the pathogen population. Nevertheless, this phenomenon was not confirmed with the P. cubensis isolates collected between the years 2002 and 2004. Metalaxyl was found ineffective, because 97% of the isolates showed the resistance to the recommended concentration (200 ,g a.i./ml), and the other 3% of isolates expressed tolerant response. The majority of the isolates showed profuse and/or limited sporulation at higher concentrations (400 and 800 ,g a.i./ml). A substantial shift to highly metalaxyl resistant strains was evident in the Czech P. cubensis populations during 2001,2004. [source] Nature of Resistance to Methyl Benzimidazole Carbamate Fungicides in Fusarium oxysporum f.sp. lilii and F. oxysporum f.sp. gladioli in TaiwanJOURNAL OF PHYTOPATHOLOGY, Issue 11-12 2009Wen Hsin Chung Abstract Fusarium oxysporum f.sp. gladioli and F. oxysporum f.sp. lilii cause corm rot and yellowing of gladiolus and lilies respectively. Resistance among isolates of these two pathogens to two benzimidazole (methyl benzimidazole carbamate: MBC) fungicides, benomyl and thiabendazole, has been identified. However, sensitivity to other benzimidazole fungicides among isolates of F. oxysporum f.sp. gladioli and F. oxysporum f.sp. lilii remains unclear. Sensitivity among isolates of these two pathogens to benomyl, thiophanate-methyl, carbendazim and thiabendazole were evaluated in this study. Results showed that among six F. oxysporum f.sp. gladioli isolates, one was highly resistant, four were moderately resistant and one was highly sensitive to benomyl, five were highly resistant to thiophanate-methyl, four were sensitive and one was highly sensitive to carbendazim and all six isolates were sensitive to thiabendazole. Among the 13 F. oxysporum f.sp. lilii isolates tested, three were moderately resistant and 10 were highly sensitive to benomyl, and five were highly resistant, three were moderately resistant and five were sensitive to thiophanate-methyl. While all isolates were highly sensitive or sensitive to carbendazim and thiabendazole. These results strongly suggest that the mode of fungicide resistance in these two pathogens varies among members of the benzimidazole fungicide group and that cross resistance does not always occur. Sequence analysis of the partially amplified , -tubulin gene indicated that mutation in codons 198 and 200 had not occurred in the benzimidazole resistant isolates. It was concluded that resistance found in Taiwan isolates of F. oxysporum f.sp. gladioli and F. oxysporum f.sp. lilii to these fungicides may be due to some other mechanism. [source] Combating plant diseases,the Darwin connectionPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 11 2009Derek W Hollomon Abstract Although Darwin knew of plant diseases, he did not study them as part of his analysis of natural selection. Effective plant disease control has only been developed after his death. This article explores the relevance of Darwin's ideas to three problem areas with respect to diseases caused by fungi: emergence of new diseases, loss of disease resistance bred into plants and development of fungicide resistance. Darwin's concept of change through natural or artificial selection relied on selection of many small changes, but subsequent genetic research has shown that change can also occur through large steps. Appearance of new diseases can involve gene duplication, transfer or recombination, but all evidence points to both host plant resistance and fungicide susceptibility being overcome through point mutations. Because the population size of diseases such as rusts and powdery and downy mildews is so large, all possible point mutations are likely to occur daily, even during moderate epidemics. Overcoming control measures therefore reflects the overall fitness of these mutants, and much resource effort is being directed towards assessment of their fitness, both in the presence and in the absence of selection. While recent developments in comparative genomics have caused some revision of Darwin's ideas, experience in managing plant disease control measures clearly demonstrates the relevance of concepts he introduced 150 years ago. It also reveals the remarkable speed and the practical impact of adaptation in wild microorganism populations to changes in their environment, and the difficulty of stopping or delaying such adaptation. Copyright © 2009 Society of Chemical Industry [source] Nested PCR-RFLP is a high-speed method to detect fungicide-resistant Botrytis cinerea at an early growth stage of grapesPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 2 2009Seiya Saito Abstract BACKGROUND: Grey mould caused by the fungus Botrytis cinerea Pers. ex Fr. is one of the major diseases in grapes. The use of fungicides is a simple strategy to protect grapes against B. cinerea disease. However, phenotypes exhibiting resistance to fungicides have been detected in B. cinerea populations. The variation of fungicide-resistant B. cinerea isolates renders B. cinerea disease control difficult in grapevine fields. RESULTS: The authors have developed a nested polymerase chain reaction,restriction fragment length polymorphism (PCR-RFLP) method to detect fungicide-resistant B. cinerea isolates at an early growth stage of grapes in grapevine fields. The nested PCR-RFLP method was carried out to detect benzimidazole-, phenylcarbamate- and/or dicarboximide-resistant B. cinerea isolates from grape berries and leaves at Eichorn,Lorenz growth stage 25 to 29. This method successfully detected fungicide-resistant B. cinerea isolates at an early growth stage of grapes. In addition, only 8 h was required from tissue sampling to phenotyping of fungicide resistance of the isolates. CONCLUSION: It is proposed that the early diagnosis of fungicide-resistant B. cinerea isolates would contribute to further improvement of integrated pest management against B. cinerea in grapevine fields, and that the nested PCR-RFLP method is a high-speed, sensitive and reliable tool for this purpose. Copyright © 2008 Society of Chemical Industry [source] Review: Alternatives to synthetic fungicides for Botrytis cinerea management in vineyardsAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 1 2010M.A. JACOMETTI Abstract Botrytis cinerea (Pers.: Fr), the causal agent of botrytis bunch rot, is an important disease of grapevines worldwide, with canopy management and the prophylactic use of fungicides being the most common control methods. The latter has resulted in fungicide resistance and is increasingly raising concerns regarding residues in wine and effects on human and environmental health. Research-led alternatives to this practice are beginning to emerge, including a range of biotic and abiotic treatments that induce vine resistance to B. cinerea and inundative applications of biological control agents such as Trichoderma, Bacillus, Ulocladium and Streptomyces species. Also, habitat manipulation techniques that aim to improve the effectiveness of naturally occurring biological control are being developed using mulches brought into the vineyard, as well as mulched cover crops. These can accelerate decomposition of botrytis mycelium and sclerotia on the vineyard floor in winter. The challenges of these different techniques and the prospects for habitat manipulation for this fungal disease are discussed. Extensive tables on synthetic fungicides, biofungicides, essential oils and plant extracts effective against B. cinerea are included. [source] | ||||||||||