Comprehension of resistance to diseases in chestnut

Ink disease (caused by the pathogen Phytophthora cinnamomi) and chestnut blight (caused by the fungus Cryphonectria parasitica) are the two most destructive diseases affecting European chestnut (Castanea sativa) and American chestnut (C. dentata). Therefore, breeding for resistance to both pathogens is essential for the chestnut sustainability in Europe and the United States of America. Several genomic approaches have been implemented in order to map the resistance first to ink disease and then to blight chestnut using a hybrid population: C. sativa crossed with resistant Asian species (C. crenata and C. mollissima). The transcriptome of C. sativa and C. crenata inoculated and not with P. cinnamomi was recently sequenced and allowed the identification of genes putatively involved in ink disease resistance. Taking advantage of molecular markers (microsatellite and SNPs), developed from the referred tanscriptomes and from C. mollissima transcriptome, the first C. sativa x C. crenata genetic map was constructed. Additionally, a reliable phenotyping method was established to evaluate the level of P. cinnamomi resistance of each hybrid allowing the identification of two Quantitative Trait Loci (QTLs). These results are the first step for understanding the resistance to ink disease in chestnut.