Genetic variation of growth and leaf phenotypic traits of Toona sinensis (A. Juss.) Roem. germplasms

Using 84 germplasms of Toona sinensis (A. Juss.) Roem., two growth traits and 18 leaf traits (including six quality traits and 12 quantitative traits) were determined. Results showed that the six leaf quality traits of the T. sinensis germplasms were rich in variability and showed polymorphism, and the main phenotypes of single traits were 1-2. The differences among germplasms in regard to 14 quantitative traits, including height, diameter, and leaf traits, were highly significant at the 0.01 level, and the genetic variance component of the other traits was larger than the environmental variance component, except for diameter, indicating that such traits were mainly controlled genetically. The average phenotypic variation coefficient of the 14 quantitative traits was 20.35% and the average genetic variation coefficient was 16.36%. Based on phenotypic and genetic variation coefficients, petiole length showed the greatest variation among traits, whereas leaf angle was the most stable. The difference between the genetic and phenotypic variation coefficients of the traits (except ground diameter) was less than 7%. The Shannon-Weaver genetic diversity index of different traits was similar (1.892-2.069), indicating that the T. sinensis germplasms exhibited high genetic diversity and a good basis for genetic improvement. The T. sinensis germplasms were divided into five groups based on cluster analysis. Group Ⅰ was characterized by strong growth and low specific leaf weight; group Ⅱ grew relatively fast and the leaves were relatively large; group Ⅲ contained the largest number of germplasms, which showed slow growth and large specific leaf weight; group Ⅳ was characterized by large leaves and multi-leaf type; and, group Ⅴ was characterized by small and sparse leaves. Thus, this study showed that the T. sinensis germplasm was rich in genetic variation and diversity and could provide abundant materials for genetic breeding and improvement.