Ithtara 



Rubira 



H7338019 



TaTao5/Loy«ll 



BY520-8 



Bailey 



Starti's Redleaf 



HIgama 



TN281-1 



Montclar 



Guardian 



40 60 80 100 



Trunk cross-sectional area 



120 



140 



Figure 1 . Trunk cross-sectional area (cm-) of Redhaven trees on several rootstocks 

 in the Massachusetts planting of the 1994 NC-140 Peach Rootstock Trial. 



As noted in the previous article, trunk cross-sectional 

 area is a universally used method to compare tree size of 

 different treatments. It relates directly to the size of the 

 canopy, and therefore allows a rough comparison of relative 

 planting density. Most of the 13 rootstocks in this trial 

 produce a tree that could be considered standard sized 

 (Table 1, Figure). Trees on Guardian and those on Lovell 

 were the largest in this category, but not significantly larger 

 than those on TaTao5/Lovell, By520-8, Bailey, Stark's 

 Redleaf, GF305, Higama, TN281-1, or Montclar. Trees on 

 Ishtara, Rubira, and H7338019 were significantly smaller 

 than those on Lovell or Guardian, and trees on Ishtara were 

 significantly smaller than all other except those on Rubira or 

 H7338019. The size of trees on Ishtara is strikingly smaller 



than that of the others, and 

 these trees required signifi- 

 cantly less time to prune. 



Yield per tree (Table 1) 

 was directly related to tree 

 size, but the ultimate assess- 

 ment would be yield per acre. 

 Because resources and time 

 are not available to conduct 

 accurate assessments of real 

 yield potential per acre, it is 

 customary to use yield effi- 

 ciency to relate yield to tree 

 size. The relative differences 

 in yield efficiency among 

 rootstocks may reflect differ- 

 ences in potential yield per 

 acre. Cumulative yield effi- 

 ciency (1996-2000) did not 

 vary greatly in this trial (Table 

 1). Trees on Ishtara, however 

 were significantly more yield 

 efficient than those on Lovell, 

 Guardian, Montclar, or 

 TaTao5/Lovell. 



Fruit size can be affected 

 by rootstock; however, root- 

 stock did not affect fruit size in this trial in 2000 or on 

 average from 1996-2000 (Table 1). 



This study will conclude after three more seasons, but 

 we can make some conclusions at this point. Particularly, 

 few differences exist among trees on the bulk of the 

 rootstocks involved in this trial. One rootstock, Ishtara, 

 however, attracts interest. It produces a small tree with 

 reduced pruning requirements, and it is productive. Further, 

 when the planting was attacked by peach tree borers a few 

 years ago, Ishtara was resistant. It is interesting to note that 

 Ishtara is the result of a peach x plum cross. All in all, this 

 rootstock IS worthy of further trial and possibly limited 

 commercial test planting. 



'k 'k i: ic :k 



Fruit Notes, Volume 65, 2000 



