Dormancy release is greatly affected by chilling unit (CU) accumulation. Lack of CU has a major impact on spring vegetative budbreak (VB). To understand the genetic mechanism governing the chilling requirement (CR), we conducted a QTL analysis of VB date in F1 population, derived from a cross between ‘Spadona’ (low CR) and ‘Harrow Sweet’ (high CR). Using a unique methodology of tree mobility, replicates of the same genotypes were exposed during the winter, over two consecutive years, to climates that differ greatly in their CU and to the same heat conditions to induce VB, in order to evaluate CR genetic impact and to distinguish it from the heat factor. Broad-sense heritability within locations ranged from 0.62 to 0.66. Due to a strong impact of GxE interaction, it was reduced to 0.46 for the overall mean. We examined the previously discovered apple QTLs detected in linkage groups (LG) 9 and 8, based on the synteny between the species. Our analysis confirms significant QTLs in LG8 (R2 = 12%–24%) and LG9 (R2 = 20%–38%) for all locations and years.
Bibliographical noteFunding Information:
We would like to thank Dr. Assaf Distelfeld from the Tel Aviv University for use of the equipment to evaluate SSR marker polymorphism. We would also like to thank Dr. Sigal Popovsky-Sarid for her help with genetic map positioning and QTL mapping. Funding was provided by the Ministry of Agriculture, Bet Dagan, Israel.
© 2017 Blackwell Verlag GmbH
- chilling requirement
- chilling units
- genotype x environment interaction
- linkage group
- marker-assisted selection