Apple Rootstock Info: B.9

Resulted from a cross of M.8 x ‘Red Standard’ (Krasnij Standard) from Russia. B.9 has been tested widely and is used commercially in the U.S. In general, B.9 is slightly more dwarfing than M.9 and has slightly higher yield efficiency than M.9. B.9 was selected as a dwarfing cold hardy rootstock and initial inoculation results indicated that it was as susceptible to fire blight as M.9. However, in field trials, trees grafted onto B.9 survived fire blight outbreaks better than trees on other dwarfing rootstocks. Recent reports from research conducted at the New York State Agricultural Experiments Station at Geneva, N.Y. indicate that B.9 becomes more resistant to fire blight as the tissue ages. There are two strains of B.9; the European strain has a more trailing growth habit whereas the North American strain has a more erect growth habit and these strains were compared in the 2002 NC-140 rootstock trial with ‘Gala’ as the scion cultivar. The American strain was slightly less dwarfing and produced more burr knots than the European strain and yield efficiency was similar.

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