A GBS Based High Density Genetic Map for Cranberry Fruit Rot Resistance QTL Detection

Cranberry (Vaccinium macrocarpon Aiton) is a woody perennial trailing shrub native to North America producing berries mostly used as juice or dry fruit. A main threat to cranberry production in NJ and MA is fruit rot caused by a fungal complex which can lead to a complete crop loss. The use of broad spectrum fungicides, up to 6 times a year, is effective to control the disease but raises residue and environmental concerns. Four unrelated accessions in our cranberry germplasm displayed fruit-rot resistance (FRR) and were used in a breeding and selection program to introgress FRR into elite horticultural backgrounds, to reduce the fungicide requirement. We developed a high density genetic map through the use of Genotyping By Sequencing (GBS) on a bi-parental population segregating for fruit rot resistance. Each parental map consists of about 3000 markers and putative FRR QTLs were identified. These maps were also used to identify potential QTLs for yield, fruit weight, and other traits. These results, combined with previous studies, provide important tools that will be used for candidate gene discovery and pyramiding of FRR QTLs from various germplasm accessions.