Baltic fruit rootstock studies: evaluation of 12 apple rootstocks in NorthEast Europe.

Abstract Within the framework of the project "Baltic fruit rootstock studies", apple rootstocks M.26, M.9, P 22, P 59, P 61, P 62, P 66, P 67, B.396, PB.4 and Pure 1 were tested with the cv. 'Ligol' over the years [2005][2006][2007][2008][2009][2010] in Estonia, Latvia, Lithuania and Poland. The vigour of trees on PB.4, P 61, P 59, P 22 and Pure 1 rootstocks was lower than that on M.9; on P 62, P 66, P 67 and B.396 it was similar to that on M.9, and more vigorous on M.26. Apple trees on the most dwarfing P 22, P 59, P 61 and PB.4 rootstocks together with Pure 1 and P 67 had significantly higher cumulative yield efficiency on average over all locations. Nevertheless rootstock effect on the cumulative yield efficiency was modified by the effect of trial location. Rootstock effect on fruit weight was relatively low. In average, P 62 developed the biggest fruit weight, whilst the lowest fruit weight was recorded on P 59. Results of rootstock effect on fruit colouring varied among trial locations. Due to desirable growth vigour, high yield and yield efficiency, rootstocks P 67 and B.396 are a good replacement of M.9 in the areas where high winterhardiness of rootstocks is required