Applications of Cell and Tissue Culture in Tree Improvement

Summary

Trees of value in agriculture and forestry require different strategies in tree improvement. Forest trees continue to require domestication because many of the superior trees have been harvested and the remainder are disappearing from natural stands at an alarming rate. By contrast, fruit, nut and ornamental trees, being already domesticated and cloned, could benefit from wider genetic variation. Global problems of increasing human populations, diminishing resources, both renewable and non-renewable, and crises of various types, e.g. food, energy, environmental, demand improved strategies for woody perennials. These should maintain existing genetic gains by clonal propagation, introduce new variation using classical and modern biotechnologies, and reduce risks by the management of germplasm through cell, life, production and utilization cycles.

Genetic gains can now be captured by somatic embryogenesis and polyembryogenesis in cell suspension culture. Cells can be cryopreserved until genotype x environment x maturity state interactions are worked out for precise environmental adaptation. The recent availability of morphogenic protoplasts creates opportunities to construct novel hybrids through cell fusion and genetic engineering. In forestry, the production of artificial seeds throughout the year provides a complementary technology to reduce risks in the practice of seed orchards where seed production is erratic and uncertain. In fruit crops, the rescue of somatic embryos based on controlled crosses contribute to wider genetic variation. Cell lines from a variety of explant sources throughout the life cycle now enable the study of somatic parthenocarpy, and enhance opportunities for the production of secondary products in vitro (directed totipotency).