Looking for the “silver bullet” -- can one test do it all?

Abstract

Seedling quality tests should ideally fulfill several conceptual and practical requirements which are explored in this paper. Difficulties in making predictions of seedlings' field performance arise from several constraints that are discussed. Some proposed criteria are evaluated for quality testing methods, and some new reasons are considered. The reasons for seedling quality tests have to be clearly stated as tests have different purposes during nursery culture, at lifting, and pre-planting. Rooted cuttings (stecklings) and seedlings produced using embryogenesis (emblings) have additional quality requirements. Eleven rating criteria for seedling quality tests are proposed and the feasibility of using anyone of the 11 tests as a “silver bullet” are assessed using these criteria. New purposes for seedling testing will result from the forest management goals of genetic diversity, diversification in use of silvicultural systems, and climate change. Future tests may apply results of molecular genetics research on gene expression and genome mapping. Expert systems will become available which will integrate and build on existing data. Seedling morphology will remain the basis for stock type selection and an important characteristic of stock quality. Nursery production should aim for uniform planting stocks wherein the need for culling is minimized, but batch culling is possible. “A silver bullet” does not exist as no single test can be applied throughout the nursery culture, lifting and pre-planting stages for all species and conditions. However, continuing emphasis on quality has resulted in detailed characterization of the whole nursery growing environment, suggestions of major areas for improvement, and increased field performance. Future research efforts should focus on a better understanding of acclimatization of seedlings on the planting site.