Massachusetts Horticultural Research Center in Belchertown, MA. To assess the 

 effects of rootstock on fruit ripening, quality, and size, 7 of the 10 

 replications were used, 5 planted in 1980 and 2 planted in 1981. 



Starting on September 15, 1986, and continuing at 5 day intervals until 

 October 5, four fruit from each tree were harvested for the measurement of 

 internal ethylene levels. One-ml gas samples were taken from the core of each 

 apple to determine the ethylene concentration. 



On September 29, 1986 ten fruit were harvested from each tree for the 

 assessment of fruit weight, length/diameter (L/D) ratio, flesh firmness, 

 percent soluble solids, and watercore incidence. Firmness was measured with an 

 Effegi Penetrometer with a 1 cm head. The percent soluble solids was assessed 

 with a hand ref ractometer , and watercore was characterized by visual assessment 

 using the method of Bramlage and Lord (1). 



Results and Discussion 



Table 1 reports the fruit weight, firmness, L/D ratio, percent soluble 

 solids, and watercore incidence. To accurately assess the effects of rootstock 

 on fruit size it is necessary to account for crop load. Table 1 also includes 

 an estimate of crop load in terms of weight of fruit per unit of trunk cross- 

 sectional area. Additional statistical analyses were performed on these data 

 to remove the effect of crop load from that of rootstock, and the differences 

 shown in Table 1 are true estimates of the effects of rootstock on size. Trees 

 on M.9 produced the largest fruit and those on M.27 EMLA and OAR 1 produced the 



Table 1. Fruit parameters and crop load for Starkspur Supreme Delicious trees 

 on various rootstocks. 



^Watercore index: 1 = not present; 5 = most severe. 



yTCA = trunk cross-sectional area. 



^Means in a column not followed by the same letter are significantly different, 



