8 



Figure 2 shows the moan internal ethylene concentration for all harvests, 

 and it is obvious that M.27 fclMLA and Ott.3 resulted in higher levels and MAC 9 



0.8 



Ethylene (ppm) 



0.0 



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



ROOTSTOCK 



MAC9 MAC24 OARl 



Figure 2. The mean, internal ethylene concentration of fruit harvested 

 September 15, 20, 25, and 30 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). 



resulted in lower levels. These data confirm the effect of these rootstocks on 

 ripening, showing a significant delay in the rise in internal ethylene caused 

 by MAC 9 and enhancement caused by M.27 EMLA and Ott.3. Additional 

 confirmation is provided by the data in Figure 3. This graph shows the 

 postharvest ripening rate of fruit from trees on the various rootstocks. Fruit 

 from trees on MAC 9 ripened the slowest and those from trees on M.27 EMLA 

 ripened fastest, suggesting that the fruit from MAC 9 were less mature when 

 harvested than those from M.27 EMLA. 



The ethylene measurements support the suggestion of the soluble solids and 

 watercore data that M.27 EMLA encouraged earlier ripening, whereas MAC 9 

 delayed ripening. 



Cone lusions 



The results from the first year of this study suggest that rootstocks can 

 alter fruit size, fruit quality (in terms of soluble solids and the incidence 

 of watercore), and the time of fruit ripening. In 1986 M.9 resulted in the 



