Effects of lower top-grafting on growth and photosynthesis of apple trees

Abstract：Lower top-grafting is a new technique to renovate and update the severe rot damaged apple trees.This study provides a theoretical basis for the use of lower top-grafting.In the experiment,two varieties which were planted in 1995 and top-grafted in 2006 were used to study the growth and photosynthesis characteristics.The result showed that the growing speed of the lower top-grafted Red Fuji and Gala is slower than the normal top grafted ones in the first three year,but faster in the following years.In the fifth year after lower top-grafting,the height of the lower top-grafted trees is 2.8 to 3.3 m,the number of the branches on the central leader is 40 to 57,and mostly concentrated on the part of central leader of 3 to 4 years old.Gala has the highest amount of branches of 651,followed by Red Fuji of 563.In the fifth year after lower top-grafting,the yield of Red Fuji is 25 080 kg per hm2.Rot disease incidence is lower by 5%.The yield of Gala is 21 089 kg per hm2.Rot disease incidence is lower by 5.5%.The net photosynthetic rate of the lower top-grafted Red Fuji is higher than the normal top grafted ones.The net photosynthetic rate of the lower top-grafted Gala is similar to the normal top grafted ones.It may be concluded that lower top-grafting is effective in preventing the rot incidence.After four years,the tree growth is even better than the traditional top grafted trees.Lower top-grafting has provided a new technology for the reform of closed orchard.