largest fruit, while M.27 EMLA and OAR 1 resulted in the smallest fruit. 

 Ripening was enhanced by M.27 EMLA, resulting in higher soluble solids levels, 

 more watercore, an earlier increase in internal ethylene, and faster post- 



Days to 1 ppm Ethylene 



Ott.3 M.7E M.9AE M.26E M.27E M.9 



ROOTSTOCK 



MAC9 MAC24 OARl 



Figure 3. The mean, postharvest ripening rate (days to reach 1 ppm internal 

 ethylene) of fruit harvested September 15 and 20 from Starkspur Supreme 

 Delicious trees on the rootstocks included in this study. E refers to those 

 rootstocks derived from EMLA clones. Bars with different letters represent 

 means that are significantly different at the 5 % level (Duncan's New Multiple 

 Range Test). 



harvest ripening rate. MAC 9 delayed ripening, resulting in lower soluble 

 solids levels, less watercore, a later increase in internal ethylene, and a 

 slower postharvest ripening rate. Study of these effects will continue in 1987 

 to confirm the results presented here. 



Are rootstock effects on fruit ripening of commercial significance? The 

 delay that may be provided by MAC 9 (Mark) may only be a few days, but it may 

 be of some help in expanding the harvest season for a single cultivar. Strains 

 of some cultivars are now available which ripen somewhat earlier than normal. 

 If these strains are combined with rootstocks which encourage earlier ripening 

 and the standard strains are combined with rootstocks, like Mark, which delay 

 ripening, significant expansions of the harvest season may be obtained. If 

 Alar* is not available for drop control in the future, it will be necessary to 

 use techniques like the one suggested here for cultivars such as Mcintosh to 

 allow harvest of the entire crop. 



