S01 - Session O8 - Using a genome wide association study to assist new apple cultivar development in mitigating climate change effects

Authors: Xiaoying Chen, Satish Kumar, Cecilia Deng, Ben van Hooijdonk, Erika Varkonyi-Gasic, Janne Lempe, James Millner, Claudia Wiedow, Svetla Sofkova-Bobcheva, Andreas Peil, Henryk Flachowsky, Vincent Bus *

There is increasing evidence globally of the impacts of climate change on apple production. Anticipated consequences of rising temperatures are reduced winter chill hours negatively affecting bud break and flowering, and an increase in fire blight incidence. Most current commercial cultivars require a high amount of winter chill and are susceptible to fire blight and. Genetic improvement for these traits could provide the adaptation required to overcome growing challenges that climate change brings. Here, we present preliminary findings from a genome wide association study (GWAS) on these traits in apple. A germplasm population of 400 accessions held at PFR has been previously genotyped using the apple 20K single-nucleotide polymorphism (SNP) array. In 2020, a subset of 85 germplasm accessions was screened for shoot resistance to fire blight in a greenhouse, while the whole germplasm population was phenotyped in the field for bud break traits. Simultaneously in Germany, a complementary genetic mapping study using an F1 population was conducted to gain knowledge on the genetic regulation of apple bud break. Preliminary GWAS marker-trait association results showed that the SNPs significantly associated with these two target traits were located in multiple genomic regions. Based on records of bud break date, showing a range of 204n293 (Julian days) with a Normal distribution, the bud break-associated SNPs were located on chromosomes 1, 4, 8 and 16. The SNPs showing association with fire blight resistance resided on chromosomes 3, 6, 12 and 15. Further phenotypic data will be collected to identify and validate the genomic regions underpinning the regulation of bud break fire and blight resistance. This research will identify germplasm with fire blight resistance and/or early bud break as well as contribute to the development of marker-assisted selection to accelerate the breeding of new apple cultivars adapted to changing climatic conditions.