Effects of polysaccharides from Botryotinia fuckeliana (Botrytis cinerea) on in vitro culture of table and wine grapes (Vitis vinifera)

Shoots of several table and wine grape cultivars were cultured in vitro on a medium supplemented with polysaccharides obtained from a culture filtrate of Botryotinia fuckeliana through differential ethanolic precipitations. The general effects of polysaccharides resulted in leaf yellowness and in a reduction of fresh and dry weight. Differential response of assayed cultivars to polysaccharides seemed to be not related to their bunch susceptibility to grey mould under field conditions

A ready-to-use single- and Duplex-TaqMan-qPCR assay to detect and quantify the biocontrol agents Trichoderma asperellum and Trichoderma gamsii

Trichoderma asperellum strain icc012 and Trichoderma gamsii strain icc080, the microbial active ingredients of Remedier™ (ISAGRO, Novara, Italy), are biocontrol agents (BCAs) employable for crop protection against a wide range of fungal pathogens, including soil-borne pathogens and fungi involved in grapevine trunk disease. In this study, single and duplex real-time quantitative PCR (qPCR) methods to detect and quantify T. asperellum and T. gamsii were developed. Primers/probe sets were designed on the T. asperellum and T. gamsii rpb2 genes and tested for specificity on a panel of microorganisms commonly associated with grape wood and soil. No differences were observed comparing single- and duplex-qPCR assays on different BCAs, 1 pg of target DNA was detected approximately at Cq= 34. R2-values and the efficiency were always equal to 0.99 and > 80%, respectively. The detection limit of the duplex-qPCR assay on artificially inoculated samples was 2 × 103and 4 × 104conidia g-1of grape wood tissue and soil, respectively. The methods will be useful to better schedule BCA application in the field and in grapevine nurseries, as well as for investigating the dynamic of BCA populations

Fungicide-Driven Evolution and Molecular Basis of Multidrug Resistance in Field Populations of the Grey Mould Fungus Botrytis cinerea

The grey mould fungus Botrytis cinerea causes losses of commercially important fruits, vegetables and ornamentals worldwide. Fungicide treatments are effective for disease control, but bear the risk of resistance development. The major resistance mechanism in fungi is target protein modification resulting in reduced drug binding. Multiple drug resistance (MDR) caused by increased efflux activity is common in human pathogenic microbes, but rarely described for plant pathogens. Annual monitoring for fungicide resistance in field isolates from fungicide-treated vineyards in France and Germany revealed a rapidly increasing appearance of B. cinerea field populations with three distinct MDR phenotypes. All MDR strains showed increased fungicide efflux activity and overexpression of efflux transporter genes. Similar to clinical MDR isolates of Candida yeasts that are due to transcription factor mutations, all MDR1 strains were shown to harbor activating mutations in a transcription factor (Mrr1) that controls the gene encoding ABC transporter AtrB. MDR2 strains had undergone a unique rearrangement in the promoter region of the major facilitator superfamily transporter gene mfsM2, induced by insertion of a retrotransposon-derived sequence. MDR2 strains carrying the same rearranged mfsM2 allele have probably migrated from French to German wine-growing regions. The roles of atrB, mrr1 and mfsM2 were proven by the phenotypes of knock-out and overexpression mutants. As confirmed by sexual crosses, combinations of mrr1 and mfsM2 mutations lead to MDR3 strains with higher broad-spectrum resistance. An MDR3 strain was shown in field experiments to be selected against sensitive strains by fungicide treatments. Our data document for the first time the rising prevalence, spread and molecular basis of MDR populations in a major plant pathogen in agricultural environments. These populations will increase the risk of grey mould rot and hamper the effectiveness of current strategies for fungicide resistance management