Effects of size-controlling apple rootstocks on certain fruit characteristics of two apple varieties

The objective of this study was to determine the effects of size-controlling apple rootstocks on fruit characteristics of two apple cultivars. Rootstocks selected were EM VII, MM 106, EM II5 MM 104, MM 111 and MM 109. Cultivars grown on these rootstocks were Red Delicious and Golden Delicious.

Factors studied were firmness, soluble solids, weight, pH, titratable acidity and reducing sugars. These factors were determined for fruits at harvest, and after six and twelve weeks storage at 34°F.

Fruits from trees on MM 109 rootstock were generally more firm than fruits from trees on the other rootstocks at harvest. This was thought to be associated with tree density. No differences in firmness was found after six and twelve weeks storage.

Statistically significant differences in fruit soluble solids due to rootstock were found. Due to wide differences between years, however, it is concluded that rootstocks had no influence on soluble solids.

Rootstock had no major effect on fruit weight. Little weight was lost during the storage period.

Fruits from trees on EM VII had a low pH whereas fruits from trees on MM 111 had a high pH. Titratable acidity was not greatly affected by rootstock. Acidity decreased with length of storage.

Reducing sugars of fruits were not greatly influenced by rootstock at harvest. However, fruits from trees on MM 104 showed a fast rate of decline in reducing sugars with six weeks of storage. This was much more prominent with Golden Delicious than with Red Delicious fruits.