Fungicide Resistance in Cucurbit Powdery Mildew: Experiences and Challenges

摘要: Fungicides are an important tool for managing cucurbit powdery mildew, which is a major production problem in many areas of the world (89). Application fungicides presently principal practice most crops mildew. that systemic or have translaminar activity needed to obtain adequate protection abaxial leaf surfaces, where conditions more favorable development pathogen than on adaxial surfaces (Figs. 1 and 2) (80). Unfortunately, these generally high risk developing resistance because they specific modes action, mildew fungi potential development. This has been especially true predominate fungus, Podosphaera (sect. Sphaerotheca) xanthii (Castagne) U. Braun & N. Shishkoff (also known as Sphaerotheca fusca (Fr.) S. Blumer fuliginea (Schlechtend.:Fr.) Pollacci). Fungicide stable, inheritable adjustment by fungus fungicide, resulting reduced sensitivity fungicide. ability obtained through evolutionary processes. Systemic at-risk contact typically specific, single-site mode means active against only one point metabolic pathway pathogen. When results from modification single gene, pathogens either resistant sensitive pesticide, disruptive selection occurs. Resistance this case seen complete loss disease control cannot be regained using higher rates frequent fungicide applications. type commonly referred “qualitative resistance” exemplified benzimidazole fungicides, conformational change at target site various pathogens. several interacting genes, exhibit range depending number gene changes. Variation within population continuous unimodal, occurs directional manner. erosion can Additional may eventually result control. “quantitative demethylation inhibiting (DMI) fungicides. Several mechanisms DMI seem operating plant based broad phenotypic sensitivities observed (32,48). Possible mechanisms, identified mainly work with model fungal systems, include decreased accumulation due increased efflux uptake, deficiency site, affinity tolerance toxic sterols, detoxifi-