Allelic Characterization of Two Genes Putatively Involved in Bitter Pit in Malus x domestica

Apple is a member of the Rosaceae, one of the most important families for world agriculture. One of the main problems that reduces apple quality both at harvest and after storage is bitter pit. Bitter pit is a nutritional disorder, due to a calcium deficiency, that results in localized cell death which appears as black pits on the fruits. Previous work in the Dhingra lab identified two putative bitter pit associated genes in apple. Initial screen of these two genes in 8 cultivars (‘Macintosh’, ‘Winesap’, Red Gravenstein’, ‘Haralson’, ‘Cox Orange’, ‘Braeburn’, ‘Honeycrisp’ and ‘Golden Delicious’) with different bitter pit susceptibility were cloned and sequenced and SNPs were identified. Using newly developed software called CisSERS (Sharp and Koepke, in review) the cDNA sequence for the two genes was analyzed in all 8 cultivars to identify differences in restriction pattern and develop a CAPS marker. The analysis is being extended to all major commercial cultivars to discover the range of alleles present and to test the association of the allele(s) with bitter pit disorder. These markers will be used to analyze the SCRI-RosBREED germplasm for validation and association of the allele(s) with bitter pit. To evaluate the impact of the environment on the expression of the two putative genes, samples of the same cultivar (‘Golden Delicious’) cultivated in different geographical areas of Spain will also be included in the analysis.