THE NEW-ZEALAND APPLE GENOME MAPPING PROJECT - A PROGRESS REPORT

This project was initiated three years ago to support the New Zealand apple breeding programme at HortResearch and is funded by both the New Zealand Foundation for Research, Science and Technology and the New 2 ealand Apple and Pear Marketing Board. Our initial goal is to construc t a linkage map comprising RFLP, RAPD and isoenzyme markers as well as characters of importance to our breeders and this will enable the bre eders to use marker assisted selection to identify the most promising seedlings within progeny populations at an early age. Characters of in terest in the shorter term include resistances to scab, powdery mildew , woolly apple aphid and silver leaf, and in the longer term more comp lex traits such as early and late fruit maturity, fruit quality charac ters, low temperature tolerance and rootstock influences such as dwarf ing and precocity are under consideration. We are currently developing long-term plans for isolation of apple genes in association with othe r molecular biologists in HortResearch. We have used a cDNA library fr om apple flesh as a prolific source of RFLP probes and detect their hy bridization to Southern blots using a chemiluminescent method. We have screened our mapping line of seedlings for more than 160 markers so f ar (1/3 RFLP, 2/3 RAPD). Detection of in situ hybridization of key RFL P probes to metaphase chromosome preparations for the purpose of assoc iating marker linkage groups with physical chromosomes is by a digoxyg enin or biotin linked immunoassay. The project has collaborative links to apple genome mapping projects in America and Europe.