tree. 



Ottawa 3 (Figure 2) is a hardy rootstock which may 

 hold a great deal of promise. It results in a tree similar in 

 size to M.26 EMLA with a similar yielding potential. On 

 a cumulative basis through 1988 the yield efficiency (Table 



Figure 2. Starkspur Supreme Delicious on Ott.3 

 after 9 growing seasons (1980 planting). 



1) of trees on Ott.3 was second only to those on M.9 

 EMLA. Trees on Ottawa 3 appear to be sUghtly better 

 anchored than those on M.26 EMLA but in most cases will 

 require support. Ripening studies (data not shown) 

 suggest that Ott.3 may advance ripenmg. 



MAC 9 (Mark) (Figure 3) is probably the most 

 interesting rootstock in the study. Tree size after the 1988 

 growing season was similar to that of trees on M.26 and 

 Ott.3 (Table 1), and it has been one of the most productive 

 trees in the planting. On a cumulative basis through 1988 

 trees on MAC 9 were 12% more yield efficient than trees 

 on M.26 EMLA. An inherently high level of precocity can 

 be a problem with MAC 9, especially with weak cultivars. 

 Excessive fruiting can result in very little growth and 

 "runting out" of the trees. Once growth has stopped due 

 to excessive cropping it is difficult to get trees to grow 

 again. Because of the limits of the uniform planting we did 

 not thin the fruit in 1987 when the crop was excessive, thus 

 fruit size and growth were reduced significantly in 1987 and 

 the crop was very light in 1988. Trees on MAC 9 (Mark) 

 in a commercial planting must be thinned early in their life 

 to maintain good growth and fruit size. Our observations 

 suggest that MAC 9 is only somewhat better anchored than 

 M.26 EMLA, so we feel that in most cases it will benefit 

 from support, at least during the first 5 years in the ground 

 when tree structure is being estabUshed. Ripening studies 

 (data not shown) suggest that MAC 9 delays ripening, 

 which may be a very useful tool for expanding the harvest 



Figure 3. Starkspur Supreme DeUcious on MAC 9 (Mark) (left) and M.26 EMLA (right) after 8 growing 

 seasons (1981 planting). 



13 



