Studies on the resistance of apple and pear rootstocks against fireblight (Erwinia amylovora).
Eleven apple and 3 pear rootstocks were tested for resistance in 1992. Of the apple rootstocks, MM.111, M.7 and M.4 showed a high degree of resistance, M.2, M.25, M.9, M.27 and B.9 were susceptible and MM.106, M.11 and A2 highly susceptible. Of the pear rootstocks, OHF333 was highly resistant, quince BA29 susceptible and quince C highly susceptible. The most common apple rootstock in Germany, M.9, was strongly attacked in 1992 but no alternative rootstock could be found. Among the pear rootstocks, resistant OHF333 is recommended, in contrast to the susceptible quince rootstocks.