Testing of pear trees on their own roots in comparison with important used rootstocks under organic farming conditions with special regard to fire blight (E. amylovora)

摘要

Pear trees on their own roots are tested in comparison to grafted trees in growth and yieldudcharacteristics and with special regard to the tolerance to diseases, above all fire blightud(Erwinia amylovora). In spring 2004 15 randomized trees of the cultivar 'Williams' fromudthree variants (self rooted in vitro, self rooted long cuttings, grafted on Quince A) wereudplanted in a pear orchard, which was heavily infected with fire blight (Erwinia amylovora)udthe previous years. The trees were left untreated. Growth and yield characteristics, plantuddiseases and tree losses were observed. After four years the in vitro self rooted trees wereudsignificantly more vigorous in growth than those grafted on quince A. The self rooted longudcuttings were comparable in growth with grafts on quince, but showed high tree lossesudprobably due to frost damages in the first winter one year after planting. However noudinfections with Erwinia amylovora could be observed so far. In a field trial with moreudcultivars and rootstock variants planted in 2006 at two organically managed sites moreudsignificant effects are expected in the next years.