The effect of rootstock on apple tree bearing stability in a cooler climate

The effect of rootstock on apple yield, productivity and alternate bearing was investigated at the Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry during a six-year period in a full bearing orchard. Apple cultivars ‘Ligol’ and ‘Auksis’ grafted on M.26 semi-dwarf rootstock; M.9, B.396, P 66, P 67 and Pure 1 dwarf rootstocks; and P 59, P 22, P 61, P 62 and PB.4 super-dwarf rootstocks were tested. Rootstock had a significant effect on apple tree growth, average yield and cumulative yield efficiency. Alternate apple bearing did not depend on rootstock vigour. Constant correlations between bearing regularity, average yield and cumulative yield efficiency were not established and differed on a cultivar or rootstock level. On the average of both tested cultivars, a more regular apple yield was recorded on Pure 1, P 59 and B.396 rootstocks. A significantly higher alternate bearing index was established on P 67, P 62 and M.9 rootstocks.