A DNA MARKER FOR COLUMNAR GROWTH HABIT IN APPLE CONTAINS A SIMPLE SEQUENCE REPEAT

The columnar mutation 'Wijcik McIntosh' has attracted much attention b ecause of its compact growth habit, which is compatible with high-dens ity plantings. Using bulked segregant analysis, we identified several randomly amplified polymorphic DNA (RAPD) markers that displayed a clo se linkage with the columnar locus (Go), The RAPD marker that displaye d the closest linkage was end sequenced to develop a sequence tagged s ite for rapidly screening segregating populations, A simple sequence r epeat (SSR) of (GA)(17) was identified within the DNA fragment, Four a llelic forms, including an apparent null allele, could be distinguishe d among the cultivars tested. The null allele displayed close linkage with Co in two progenies, and we used this marker to identify the loca tion of the gene on the apple linkage map.