WOOD STIFFNESS AS A TRAIT FOR PHENOTYPING, SELECTIVE GENOTYPING AND PRELIMINARY GENETIC DIVERSITY ESTIMATION USING SSR MARKERS IN MELIA DUBIA

Trait specific phenotyping, selective genotyping and genetic diversity for wood stiffness was carried out in Melia dubia Cav. (Meliaceae), a native fast-growing tree species of India extensively used in plywood industry. Wood stiffness plays a major role for structural lumbers and veneer industry. To estimate it by non-destructive method, stress wave velocity was measured in standing trees (n=513) using a stress wave timer. The velocity ranged from 3.24 km/s to 4.24 km/s in trees with ≥ 37.5cm Girth at Breast Height (GBH). For selective genotyping, 20 genotypes having high (4.05- 4.46-km/s) and 27 genotypes having low (3.24- 3.94-km/s) stress wave velocity were selected. For genetic diversity estimates, 55 SSR markers were screened and 15 markers showing trait related polymorphism were selected. Analysis for genetic diversity revealed highly polymorphic loci (Na=22.2) and low level of observed heterozygosity (Ho= 0.18). In addition, the results showed positive fixation index of 0.81 which is an indicator of inbreeding. Twelve markers showed distinct dissimilarity between high and low stress wave velocity groups. Out of which, five markers, MSSR 26, 33, 37, 41 and Mc2 showed distinct alleles for high wood stiffness. Cluster analysis with 47 genotypes resulted in three major clusters of which 90% of genotypes were distinctly segregated into two clusters having either low or high wood stiffness character. Identifying more markers of above type may facilitate in future marker assisted selection programme for wood stiffness in M. dubia