Evaluation of inter-simple sequence repeat analysis for mapping the Co gene in apple (Malus pumila Mill.)

The desirable columnar trait in apple (Malus pumila Mill.) is determined by the Co gene. The first step towards cloning this gene, and the production of transgenic plants, is the construction of a saturated linkage map in the region of the Co gene. To map this gene, we used inter-simple sequence repeat (ISSR) analysis. ISSR primers (100) were first used on an F-1 population of 120 individuals. These individuals were derived from a cross between 'Fuji' (normal growth type) and 'Telamon' (columnar type). Two bulks (columnar and normal), with 20 seedlings in each, were prepared for bulked segregant analysis (BSA). For the selection of primers, BSA analysis between these gene pools was used to examine F-1 seedlings of 'Fuji' and 'Telamon' for further screening. Thirty-three ISSR markers were available for analysing cosegregation with the Co gene. The resulting linkage map of the Co gene region contained 13 markers. It was flanked by UBC834(900) from 'Fuji' with a genetic distance of 10.1 cM and UBC818(1000) from 'Telamon' with a genetic distance of 11.2 cM.