In 1990, a trial was established at 17 locations in the United States and Canada including the scions `Golden Delicious', `Jonagold', `Empire', and `Rome” and the rootstocks M.9 EMLA, B.9, Mark, O.3, and M.26 EMLA. In 1994, trees on M.26 EMLA were the largest and trees on B.9 and those on Mark were the smallest, regardless of scion. Trees on M.9 EMLA were intermediate. `Golden Delicious' and `Empire” trees on O.3 were larger than those on M.9 EMLA. `Jonagold' and `Rome' trees on O.3 were similar in size to those on M.9 EMLA. With all scions, B.9 and Mark resulted in the lowest cumulative yields. With `Jonagold', `Empire', or `Rome' as the scion, O.3, M.26 EMLA, and M.9 EMLA resulted in the greatest and similar yields. With `Golden Delicious' as the scion, however, trees on M.9 EMLA yielded only as much as those on B.9 or Mark. Trees on B.9 and those on Mark were the most yield-efficient, regardless of scion. `Golden Delicious' and `Rome' trees on O.3 were similar to those on B.9 and those on Mark, but `Jonagold' and `Empire' trees on O.3 were less efficient than those on B.9 or on Mark. Overall, M.26 EMLA resulted in the lowest efficiency; however, M.9 EMLA resulted in more efficient trees only with `Empire' as the scion. Participants include: J.L. Anderson (Utah), W.R. Autio (Mass.), J.A. Barden (Va.), G.R. Brown (Ky.), P.A. Domoto (Iowa), D.C. Ferree (Ohio), A. Gaus (Colo.), R.L. Granger (Quebec), R.A. Hayden (Ind.), F. Morrison (Kan.), C.A. Mullins (Tenn.), S.C. Myers (Ga.), R.L. Perry (Mich.), C.R. Rom (Ark.), J.R. Schupp (Maine), and L.D. Tukey (Pa.).
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