An Update on Dwarfing Rootstocks 

 in the 1984 NC-140 Apple Rootstock 

 Planting in Massachusetts 



Wesley R. Autio 



Department of Plant & Soil Sciences, University of Massachusetts 



Throughout New England there is a great deal of 

 interest in dwarfing rootstocks. The New England 

 Apple Survey, conducted in 1989, showed that only 

 14 % of the acreage planted between 1985 and 1989 

 was planted to trees on dwarfing rootstocks. Grow- 

 ers predicted, however, that from 1990 to 1994, 62 % 

 of the acreage planted would be planted to dwarfing 

 rootstocks. Many new rootstocks in the dwarfing 

 category are becoming commercially available, and 

 a number of these have been under study in Massa- 

 chusetts. Because of the host of potential problems 

 with new rootstocks, growers should be cautious 

 when new selecting rootstocks. In this article I will 

 give a brief update on some of these new rootstocks. 



In 1984, a cooperative planting of the NC-140 

 Rootstock Research Committee was established at 

 the University of Massachusetts Horticultural Re- 

 search Center in Belchertown, MA. The scion culti- 

 var was Starkspur Supreme Delicious, and the root- 

 stocks under study include Bud. 9, Bud.490, MAC 1, 

 MAC 39, P.l, P.2, P.16, P. 18, P.22, C.6, M.4, M.7 

 EMLA, M.26 EMLA, Ant.313, and seedling. The 



degree of dwarfing ranges from ultradwarf to stan- 

 dard. In this article I will report results only from 

 those in the dwarf and ultradwarf categories. 



Table 1 reports the trunk cross-sectional area, 

 yield, and yield efficiency of trees on P. 16, P.22, P.2, 

 Bud.9, MAC 39, C.6, and M.26 EMLA. Trees on P.16 

 and P.22 were ultradwarf, producing trees roughly 

 similar in size to M.27. P.2 produced a tree similar 

 in size to M.9, and Bud.9 and MAC 39 were between 

 M.9 and M.26 in size. C.6 produced a tree similar in 

 size to M.26. All 7 of these combinations need trunk 

 support. 



The highest yielding trees in 1990 and on a 

 cumulative basis were on C.6. However, because of 

 the size difference among trees on these 7 rootstocks, 

 it is necessary to compare yield efficiencies, which 

 relate yield to tree size and give a rough way to 

 compare potential yields per acre. In 1990, trees on 

 Bud.9, MAC 39, P.2, P.16, and C.6 were more effi- 

 cient than those on P.22. On a cumulative basis, 

 trees on Bud.9, P.2, P.16, and C.6 were more efficient 

 than those on MAC 39 and M.26 EMLA. 



Fruit Notes, Spring, 1991 



