Effect of interstock bridge grafting (M9 dwarfing rootstock and same cultivar cutting) on vegetative growth, reproductive growth and carbohydrate composition of mature apple trees

Four apple cultivars, Granny Smith, Cox's Orange, Gala and Oregon Red Delic ious on rootstock MM106, M793 or Northern Spy were interstock bridge grafte d with M9 dwarfing rootstock or same cultivar cuttings to investigate the e ffect on vegetative, reproductive and biochemical changes and fruit quality at harvest in different apple cultivars. Controls were also left with no i nterstock treatment. In general bridge grafting reduced shoot growth (up to 20%), increased floriferousness, changed carbohydrate (CHO) level and incr eased yield (up to 30%) with the greatest effects in the second season. The treatment did not significantly change mean fruit weight, fruit length to diameter (L/D) ratio or flesh colour in first season, while in the second s eason there were significant differences in these apple quality measures. S eed number and brix value at han est from both treatments were significantl y increased in both seasons. Flesh firmness also showed significant increas es in both seasons. The M9 bridge and same cultivar interstocks were genera lly similar in effect though occasionally the M9 had a greater effect. Inte rstock bridge grafting of mature apple trees may be a viable method of redu cing growth and improving yield. (C) 1999 Elsevier Science B.V. All rights reserved.