smallest. Note that trees on M.27 EMLA and M,9 had similar crop loads and 

 trees on OAK 1 had a very light crop, suggesting a substantial effect of 

 rootstock on fruit size. • 



Few differences were seen in fruit firmness (Table 1) and those that were 

 present can be attributed to size, the smaller fruit being firmer. The L/D 

 ratio (Table 1) was highest for fruit from trees on M.7 EMLA and smallest for 

 fruit from trees on M.27 EMLA. The differences were statistically significant 

 and may be of commercial importance. 



The percent soluble solids (Table 1) was highest for fruit from trees on 

 M.27 EMLA, whereas it was the lowest in fruit from trees on MAC 9. 

 Furthermore, watercore was most prominent in fruit from trees on M.27 EMLA and 

 MAC 24 and least prominent in fruit from trees on MAC 9. This relationship 

 suggests that there may be significant differences with respect to the timing 

 of fruit ripening, but soluble solids and watercore are not very accurate 

 indices of fruit ripening. 



During the course of ripening, apples exhibit a very rapid rise in the 

 biosynthesis of ethylene, a gaseous plant hormone. Within the core area the 

 concentration of ethylene rises with the increase in biosynthesis, providing a 

 very accurate means of comparing the times of ripening. Figure 1 shows the 

 internal ethylene concentration of apples from trees on M.27 EMLA, M.7 EMLA, 

 and MAC 9. Other rootstocks were deleted from the graph to avoid confusion, 

 but were roughly grouped into 3 patterns. Generally, M.27 EMLA (along with 

 Ott.3, M.9, and M.9A EMLA) encouraged the earliest increase in internal 

 ethylene. M.7 EMLA (along with M.26 EMLA, MAC 24, and OAR 1) resulted in a 

 somewhat later rise, and MAC 9 delayed the increase in internal ethylene. 



12 



Ethylene (ppm) 



10 h 



8 



2 - 



M.27 EMLA 



M.7 EMLA 



— *— 

 9/15 



MAC 9 



A 



9/20 



9/30 



10/5 



Figure 1. The internal ethylene concentration of Starkspur Supreme Delicious 

 fruit immediately after harvest from trees on MAC 9, M.7 EMLA, or M.27 EMLA. 



