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)

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

Effects of pre-severance irradiance on the growth of Allanblackia floribunda Oliv. stockplants and on the subsequent rooting capacity of leafy stem cuttings

The rooting of Allanblackia stem cuttings is typically slow and with the formation of very few roots. Irradiance has positive effects on the relative growth of plants and rooting ability, but there is no information relating to Allanblackia species. Stumps of Allanblackia floribunda Oliv. were grown under three levels of irradiance (2008 mu molm(-2)s(-1), 542 mu molm(-2)s(-1) and 160 mu molm(-2)s(-1)) and were assessed for growth (plant height and the number of cuttings) and the influence of irradiance on the rooting ability of leafy stem cuttings. Shade light regime 542 mu molm(-2)s(-1) resulted in significantly greater stockplant height than in 160 and 2008 mu molm(-2)s(-1). Significantly more useable cuttings were harvested from the tall plants under an irradiance of 542 mu molm(-2)s(-1), fewer from 160 mu molm(-2)s(-1), and the least from 2008 mu molm(-2)s(-1). The rooting ability of cuttings was greatest from stockplants receiving 542 mu molm(-2)s(-1) (>60%) and least from those receiving 160 mu molm(-2)s(-1) (20%). 45% of cutting rooted from stockplants under full sun (2008 mu molm(-2)s(-1)). The speed of rooting of cuttings followed the same ranking with the fastest rooting from plants receiving 542 mu molm(-2)s(-1) (7.1 +/- 1.04weeks to reach 25% of rooting) and the slowest from those under 160 mu molm(-2)s(-1) (12.3 +/- 1.85weeks to reach 25% of rooting). The results of this study demonstrate that the light management of A. floribunda stockplants is important for the maximization of the yielding of cutting and the speed of rooting of leafy stem cuttings. Tree plantation being a key option to alleviate environmental challenges that the world is facing today, these results confirm previous findings which postulates that appropriate light management in stockplants can increase the production speed of required seedlings

Iodine isotopes species fingerprinting environmental conditions in surface water along the northeastern Atlantic Ocean

Concentrations and species of iodine isotopes (I-127 and I-129) provide vital information about iodine geochemistry, environmental conditions and water masses exchange in oceans. Despite extensive investigations of anthropogenic I-129 in the Arctic Ocean and the Nordic Seas, concentrations of the isotope in the Atlantic Ocean are, however, still unknown. We here present first data on I-129 and I-127, and their species (iodide and iodate) in surface water transect along the northeastern Atlantic between 30 degrees and 50 degrees N. The results show iodate as the predominant species in the analyzed marine waters for both I-127 and I-129. Despite the rather constant ratios of I-127(-)/(IO3-)-I-127, the I-129(-)/(IO3-)-I-129 values reveal variations that apparently response to sources, environmental conditions and residence time. These findings provide a new tracer approach that will strongly enhance the application of anthropogenic I-129 in ocean environments and impact on climate at the ocean boundary layer