Selection and Breeding of Willows {Salix spp.) for Short Rotation Forestry

摘要

The clonal tests of the arborescent willows in Croatia include the autochthonous white wiftow {Salix alba), interracial hybrids of the autochthonous white willow and the English 'cricket' willow (S. alba var. calva), interspecies hybrids (S. matsudanax S. alba), as well as multispecies hybrids of willows. Selection for this purpose is done in natural populations "of white willow, white willow hybrid families, and hybrid families of white willow interspecies hybrids with other species. These are mainly the Chinese willow {Salix alba x S. matsudana) of the F, and F^ generation, as well as backcrosses. Special attention has been paid to the selectioh of the plus variants on the basis of transgression variability. Testing of arborescent willows continued aiming at identification of clones with greatest production potential, particularly on so called marginal sites i.e. abandoned agricultural soils and/or sites that are not suitable for growing more valuable tree secies. Clonal tests were established with clones originated tp white willow (Salix alba) and from different crossing combinations of white willow and Chinese willow (S. matsudarra). In one clonal test, on the heavy clay type of soils, in two-year rotation, mean biomass production of all studied clones (more than 30) was 9.3 t DM ha~(-1) The highest biomass production of white willow (Salix alba) was performed by clones 'B44', 'V093' i 'V052' (17.5, 13.7 and 12.2 t DM ha~(-1) respectively). Above mentioned clones have shown specific adaptedness on tested conditions through survivaland sprouting ability. In other two clonal tests with hybrids of white willow and Chinese willow (more than 50 clones), mean biomass produbtion vary from 10.7 to 28.8 t DM ha~(-1) a~(-1) at the first and second two year rotation period. At one of these experimental plots, with regular agrotechnical treatments, the highest biomass production as well as the best adaptedness and phenotypic stability on testing sites was shown by two clones ('V 374', 'V 461', 25,8 -27,61 DM ha~(-1) a~(-1)) originated from backcross hybrid S. matsudana x (S. matsudana x S. alba) and by one S. alba clone ('V 95', 28,8 t DM ha~(-1) a~(-1)). These results indicated significant potential of Chinese willow for further breeding aimed at biomass production in short rotations.