In the frame of ‘Baltic fruit rootstock studies’ apple rootstocks B.9, B.146, B.396, B.491, P 2, P 22, P 60, M.9, M.26, Jork 9, Bulboga and Pure 1 were tested in Estonia, Latvia and Lithuania. More vigorous tree growth was recorded following North-South direction being the weakest in Estonia and the strongest in Lithuania. Apple rootstocks can be grouped, according to the induced tree vigour, in the following way: less vigorous than M.9: P 22, the same as M.9: Pure 1, B.396, Jork 9, P 60, B.9 and P 2, between M.9 and M.26: B.491, more vigorous than M.26: Bulboga and B.146. Rootstock effect on cumulative yield and cumulative yield efficiency index was determined by location. The highest productivity, considering cumulative yield and efficiency index, was obtained on M.9 rootstock in Lithuania, on Bulboga, B.146, M.26 and B.491 rootstocks in Estonia and on Pure 1, P 60 and B.9 rootstocks in Latvia. Rootstock effect on fruit weight was not clear and differed among locations. Interactions between rootstock and location indicate at the importance of multi-site rootstock evaluation.

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.

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In 2001, investigations were carried out on the Latvian origin cultivar ‘Suvenîrs’ grafted on seven pear rootstocks (MA, MC, BA29, Pyrodwarf, Brokmal, Kirchensaller Mostbirne and Kazrauðu bumbiere) in Polli (Estonia), Pûre (Latvia) and Babtai (Lithuania). The aim of the investigation was to evaluate pear rootstocks in different climatic conditions in the Baltic region. In Polli, all trees were planted in a dense planting, and therefore, trunk cross section area did not differ significantly between trees on different rootstocks. The most vigorous tree habit was observed in Lithuania for trees grafted on the rootstocks Kirchensaller Mostbirne and Brokmal, but in Latvia on Kirchensaller Mostbirne and Kazrauðu bumbiere. The highest dwarfing effect was observed for rootstock MC in both places. The highest cumulative yield from the orchard area was found for trees grafted on rootstocks of the quince group in all three locations of investigation. Nevertheless, the winter hardiness of the quince group rootstocks was not sufficient for Baltic climatic conditions. Good overwintering in Latvia and Lithuania was observed for trees on Pyrodwarf. Survival rate of trees grafted on Pyrodwarf in Estonia was unsatisfactory. The worse overwintering in Lithuania was observed for trees grafted on Brokmal. There was a dwarfing effect on trees and better yield on the vegetative propagated rootstocks included in the investigation, but none one of them can be recommended as perspective for commercial orchards in Baltic agro-climatic conditions.

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