Rootstock Affects Ripening of 

 l\/lclntosli Apples 



Wesley R. Autio 



Department of Plant & Soil Sciences, University of Massachusetts 



Monitoring and controlling ripening is an im- 

 portant aspect of orchard management. Several 

 factors affect ripening of any particular cultivar of 

 apple, such as climate, strain, chemical treatments, 

 and crop load. Cultivars may vary in their response 

 to these factors. As an example of this variation, 

 work conducted at the Horticultural Research Cen- 

 ter a few years ago compared the effects of crop load 

 on ripening of Delicious and Golden Delicious 

 apples. Golden Delicious ripening was ten days later 

 for heavily cropping trees compared to lightly crop- 

 ping trees; whereas, Delicious at similar cropping 

 levels were different by only four days. 



Previously, I reported that rootstock affected 

 Delicious apple ripening [Fruit Notes 56 (2):8-9 and 

 56(3):3-5]. Specifically in the 1980 NC-140 Plant- 

 ing, 0.3 and M.27 EMLA advanced ripening, and 

 M.27 EMLA and OARl delayed ripening. In the 

 1984 NC-140 Planting, C.6, B.9, and M.26 EMLA 

 advanced ripening of Delicious fruit. It is conceiv- 

 able that rootstock effects on ripening may vary from 

 cultivar to cultivar. 



The study reported here was initiated to exam- 



ine the effects of rootstock on Mcintosh ripening. 

 Summerland Red Mcintosh trees on M.9/A.2, 0.3, 

 M.7 EMLA, M.26 EMLA, M.7A, OARl, and Mark 

 were planted in 1985 in a trial at the University of 

 Massachusetts Horticultural Research Center 

 (Belchertown) with seven replications. Tree size 

 and productivity were reported in Fruit Notes 

 60(1):8-11. To assess ripening differences, internal 

 ethylene concentrations in fruit were measured pe- 

 riodically each harvest seasons from 1988 through 

 1994. Further, fruit were sampled once per year 

 for the measurement of flesh firmness, soluble sol- 

 ids concentration, and starch index value fi-om 1990 

 through 1994. 



At the beginning of ripening, fruit become ca- 

 pable of producing large quantities of ethylene, and 

 internal concentrations rise dramatically through 

 the process of ripening. In this study, internal eth- 

 ylene concentrations were affected significantly by 

 rootstock (Table 1). Some variation occurred from 

 year to year, but overall, 0.3 and M.26 EMLA con- 

 sistently resulted in ethylene levels higher than 

 those of other rootstocks. Fruit from trees on OARl, 



Fruit Notes, Spring, 1996 



