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)

Summary in the original language of the document

Pear trees on their own roots are tested in comparison to grafted trees in growth and yield
characteristics and with special regard to the tolerance to diseases, above all fire blight
(Erwinia amylovora). In spring 2004 15 randomized trees of the cultivar 'Williams' from
three variants (self rooted in vitro, self rooted long cuttings, grafted on Quince A) were
planted in a pear orchard, which was heavily infected with fire blight (Erwinia amylovora)
the previous years. The trees were left untreated. Growth and yield characteristics, plant
diseases and tree losses were observed. After four years the in vitro self rooted trees were
significantly more vigorous in growth than those grafted on quince A. The self rooted long
cuttings were comparable in growth with grafts on quince, but showed high tree losses
probably due to frost damages in the first winter one year after planting. However no
infections with Erwinia amylovora could be observed so far. In a field trial with more
cultivars and rootstock variants planted in 2006 at two organically managed sites more
significant effects are expected in the next years.