established at 27 locations in 1980 and 1981 and includes 

 Starkspur Supreme Delicious on M.7 EMLA, M.9 EMLA, 

 M.26 EMLA, M.27 EMLA, M.9, OAR 1, Ottawa 3, and 

 MAC 9 (the virus-indexed version of which is now being 

 sold as "Mark"). This planting was established as a 

 randomized complete block with 10 replications. Trees in 

 half of the replications (those planted in 1981) were staked 

 at planting, while trees in the other half (those planted in 

 1980) were staked only when they leaned more than 45° 

 from vertical. Each year the height, spread, trunk 

 circumference, and yield from each tree is measured. 



The younger NC-140 planting was established in 1984 

 and includes Starkspur Supreme Delicious on Bud.9, 

 Bud.490, P.l, P.2, P.16, P.18, P.22, MAC 1, MAC 39, CG- 

 10, CG-24, M.4, M.7 EMLA, M.26 EMLA, C.6, Ant.313, 

 and domestic seedling in a randomized complete block 

 design with 10 replications. Trees have been staked only 

 when they have leaned more than 45° from vertical. 



Table 1 presents the trunk circumference and yield 

 data from the 1980 and 1981 plantings. The discussion 

 here will focus on the 3 most interesting rootstocks in the 

 1980/81 planting: M.9 EMLA, Ott.3, and MAC 9 (Mark). 



The EMLA designation refers to those rootstocks 

 derived from clones which have had the latent viruses 

 removed. They were developed by a cooperative effort of 

 the East Mailing and Long Ashton Research Stations in 

 England. In general, the EMLA series rootstocks are very 

 similar to the rootstock from which they were derived, e.g.. 



M.7 EMLA is very similar to M.7 or M.7A. In some cases 

 vigor may be slightly greater for the EMLA version; 

 however, M.9 EMLA is considerably more vigorous and 

 productive that M.9 (Figure 1). M.9 EMLA actually was 

 derived from a different strain of M.9 than we commonly 

 use. The trunk circumference after the 1988 growing 

 season of trees on M.9 EMLA was 28% greater than those 

 on M.9. The 1988 yield per tree was 308% larger, and the 

 cumulative yield per tree from 1983 through 1988 was 

 118% greater. Another way to look at yield is in terms of 

 yield efficiency (Table 1), which is given as yield per unit of 

 trunk cross-sectional area. This term accurately relates 

 tree size and yield per tree and allows a comparison of 

 potential productivity. On a cumulative basis through 1988 

 the trees on M.9 EMLA were 30% more yield efficient 

 than those on M.9. 



In general, M.9 EMLA may result in a tree which is 

 too vigorous for a trellis; however, trees on M.9 EMLA 

 may be a superior tree on a post trained to a slender spindle 

 or a similar system. It is necessary to consider cultivar 

 when choosing between M.9 and M.9 EMLA and among 

 the various training systems. These observations are based 

 primarily on a low-vigor cultivar: Starkspur Supreme 

 Delicious. With a vigorous scion M.9 may produce an 

 excellent posted tree, and M.9 EMLA may result in a tree 

 too large for a high density planting. With a low-vigor 

 cultivar the vigor induced by M.9 EMLA may be necessary 

 to allow the development of even an adequate trellised 



Figure 1. Starkspur Supreme Delicious on M.9 EMLA (left) and M.9 (right) after 8 growing seasons (1981 

 planting). 



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