Modulation of expression of the apple scab resistance gene HcrVf2 in classically bred and genetically engineered scab-resistant apple cultivars

• Applicant: Dr. Cornelia Chizzali
• Subject Area: Plant Breeding and Plant Pathology
• Term: from 2012 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 226112348

Apple production, both integrated and organic, requires more than 15 fungicide treatments a year to combat apple scab, which is caused by the fungus Venturia inaequalis. All commercially important cultivars are susceptible, only a few cultivars used in organic production contain the resistance Vf from the wild apple genotype Malus floribunda 821. The gene locus Vf contains 4 sequences, which similarly occur in tomato (homologues of Cladosporium fulvum resistance genes). One of these sequences, HcrVf2, leads to absolute resistance when transferred to the scab-susceptible apple cultivar Gala. Resistance genes are commonly thought to be constitutively expressed, however, there is indication of inoculation- and stress-dependent expression (modulation) of HcrVf2 in classically bred Vf cultivars. In contrast, modulation of this gene (with own promoter and terminator) can no longer, or not to the same extent, occur after transfer via gene technology due to the non-natural position in the apple genome. In the present work, the natural expression levels of the HcrVf2 gene in a couple of classically bred apple cultivars are compared. Differences or similarities in expression are determined in comparison to various lines of the genetically generated HcrVf2 cultivar. Modulation of expression is analyzed as a function of time and stress. The focus will be on quantitative studies of the HcrVf2 expression level in classically bred cultivars and transformed HcrVf2 lines, combined with phenotypic resistance/susceptibility data. In the debate on gene technology, especially on cisgenesis (exclusive use of species-specific genes with own promoter and terminator), position effects are considered a source of possible negative effects which, however, are neither substantiated nor disproved by scientific studies. This project will thus provide groundbreaking results.

• DFG Programme: Research Fellowships
• International Connection: Switzerland
• Host: Professor Dr. Cesare Gessler