EVALUATING 28 STRAINS OF DELICIOUS APPLE IN MICHIGAN

A cooperative experiment begun in 1980 was designed to evaluate the pr oductivity and other characteristics of 16 spur and 12 standard strain s of 'Delicious' apple on two rootstocks (M.7 EMLA and MM.111 EMLA). A ll trees were propagated at one nursery, and plantings were establishe d in Michigan, Washington, Oregon, Idaho, Indiana, and British Columbi a. In Michigan, trees of standard strains were consistently larger tha n trees of spur strains 8 years after planting. Early yields were grea ter on M.7 EMLA than on MM.111 EMLA, but trees were more subject to le aning under heavy crops on M.7 EMLA. In general, spur-type strains yie lded more fruit per unit trunk cross-sectional area than standard stra ins. Yield was more closely associated with fruit-setting ability than with flower density, and fruit size declined as fruit set increased. Length/diameter ratios and biennial bearing indices also differed sign ificantly among strains.