Genetic analysis and QTL detection for biennial bearing in apple

28. International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Organic Horticulture: Productivity and Sustainability Lisbon, Portugal, 2012/03/31Genetic determinants of biennial bearing in apple trees were investigated using a quantitative genetic strategy. The mapping population, the F1 progeny of 123 individuals, is derived from a cross between two cultivars that exhibit either biennial or annual bearing. The number of inflorescences, the number and the mass of fruit harvested per tree were recorded over six years. These data were summarized by indices such as biennial bearing (BBI), precocity (PI) and cumulative yield (CY) that were used to estimate genotypic effects and detect Quantitative Trait Loci (QTL). The variables with the highest genotypic effect were for inflorescence traits. Two genomic regions on linkage group (LG) 1 and 15 comprised several QTLs for inflorescence and fruit production. Four genomic regions were identified for production precocity on distinct and non-homologous LGs. Three QTLs were detected for BBI for the number of inflorescences and these together explained 49% of the phenotypic variability. Two common QTLs were detected on LG10 and 13 for BBI for the number and the mass of harvested fruits. Results suggest that both production precocity and biennial bearing are under multi-genetic control