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Cross-resistance between myclobutanil and tebuconazole and the genetic basis of tebuconazole resistance in Venturia inaequalis
BACKGROUND: Myclobutanil is one of the most widely used demethylation inhibitor (DMI) fungicides for the management of apple scab, caused by Venturia inaequalis. Strains of V. inaequalis resistant to myclobutanil have been reported across the world. Tebuconazole, another DMI fungicide, has been proposed as an alternative to myclobutanil, and the extent of cross-resistance with myclobutanil therefore needs to be evaluated. The sensitivity to tebuconazole and myclobutanil of a total of 40 isolates was determined. Half the isolates came from an isolated orchard which had never been sprayed with fungicides and half from orchards sprayed regularly with myclobutanil, but still with disease control problems. The progeny of a tebuconazole resistant (R) Ă sensitive (S) V. inaequalis cross were analysed in order to improve understanding of the genetic control of tebuconazole sensitivity.
RESULTS: There is cross-resistance between myclobutanil and tebuconazole (r=0.91; P < 0.001). Sensitivity to tebuconazole of the progeny of a RĂS cross varied quantitatively in a pattern which implied at least two gene loci differing between the parental strains. In addition, the asymmetric distribution of the sensitivity in the progeny implied possible epistatic effects.
CONCLUSION: Resistance to myclobutanil and tebuconazole is strongly correlated. At least two genes are involved in the control of tebuconazole resistance in V. inaequalis
Gene expression analysis distinguishes tissue-specific and gender-related functions among adult Ascaris suum tissues
Over a billion people are infected by Ascaris spp. intestinal parasites. To clarify functional differences among tissues of adult A. suum, we compared gene expression by various tissues of these worms by expression microarray methods.. The A. suum genome was sequenced and assembled to allow generation of microarray elements. Expression of over 40,000 60-mer elements was investigated in a variety of tissues from both male and female adult worms. Nearly 50 percent of the elements for which signal was detected exhibited differential expression among different tissues. The unique profile of transcripts identified for each tissue clarified functional distinctions among tissues, such as chitin binding in the ovary and peptidase activity in the intestines. Interestingly, hundreds of gender-specific elements were characterized in multiple non-reproductive tissues of female or male worms, with most prominence of gender differences in intestinal tissue. A. suum genes from the same family were frequently expressed differently among tissues. Transcript abundance for genes specific to A. suum, by comparison to Caenorhabditis elegans, varied to a greater extent among tissues than for genes conserved between A. suum and C. elegans. Analysis using C. elegans protein interaction data identified functional modules conserved between these two nematodes, resulting in identification of functional predictions of essential subnetworks of protein interactions and how these networks may vary among nematode tissues. A notable finding was very high module similarity between adult reproductive tissues and intestine. Our results provide the most comprehensive assessment of gene expression among tissues of a parasitic nematode to date