Abstract:

Fifteen tester strains of Masson Pine (Pinus massoniana) were used to investigate the relative importance of GCA and SCA for seedling growth and root parameters with a potting experiment at low and high phosphorus levels. Results showed that the seedling growth and root parameters exhibited significant differences among the tester strains and were under strong genetic control with 0.745～0.920 full sib family heritabilities at different phosphorus levels. It was found that the seedling growth and root traits were controlled more by GCA and female parent SCA than male SCA. At high phosphorus level， the seedling growth performance, and especially root traits were controlled mainly by non additive gene effect, and also influenced by the additive gene effect. Hybridization between superior parents selected from the South and the North was able to generate new hybrid varieties with more developed roots and better growth performance. The total root length， root surface area and root volume were still genetically controlled by the nonadditive gene effect at low phosphorus level， but the relative importance of GCA and SCA for seedling height， diameter and lateral root number at low phosphorus level were changed， whose GCA effect increased and SCA effect decreased obviously， compared with those at high phosphorus level. Therefore， new varieties with high phosphorus efficiency were able to be selected through the SCA breeding of specific indexes such as total root length， root surface area and root volume and so on.

Key words: Pinus massoniana, seedling, tester strain, growth, root parameter, low phosphorus stress, combining ability, heritability