Breeding

The Poplar & Willow breeding and selection programme

• develops improved, locally adapted poplar and willow clones suitable for soil conservation and river protection plantings

• maintains and enhances the germplasm collection through hybridisation and introduction of new source material


Strategy

The POPLAR breeding programme is focussed on selecting a range of clones suitable for soil conservation and windbreaks, i.e., to provide a major tree component on which to base the sustainable use of pastoral hill country. Since these soil conservation trees are planted singly, or at wide spacings in unstable pasture, they are more exposed than plantation-grown trees to damage from wind, stock grazing and trampling, and soil movement.

Important selection criteria include high resistance to current pests and diseases, high rooting ability from unrooted cuttings, rapid growth, straight stem. Desirable criteria are a basic wood density of at least 360 kg/m3 and a low incidence of pathological black heart caused by bacteria. Soil conservation trees require rough, thick bark by age 5-6 years, narrow to intermediate width crowns, high wind resistance, and low incidence of epicormic sprouting following pruning. Shelterbelt trees, in addition, require a low phototropic reaction.

The WILLOW breeding programme aims to develop tree willows which form rough bark at an early age, as protection against browsing by livestock, and with low palatability to possum and insect pests. Improvement work in willows is being directed towards the introduction and development of a wide range of species and clones of diverse genetic origin. Those showing good local adaptation, or other desirable attributes are incorporated into the breeding programme. Increasing the range of genetic material for intra- and inter-specific hybridisation is considered to be the best method of producing improved willows.

The shrub willow improvement programme develops a range of clones with bitter foliage unpalatable to possums, and also a multiple stem habit, making them suitable for gully planting, stream bank stabilisation, roadside planting and mountainland revegetation where tree willows are not suitable. Where requirements for biomass and fodder differ selection provision is made for them also.

Clonal Releases

Male clones are favoured for release, other attributes being equal.