COMPARATIVE GENETIC DIVERSITY STUDIES OF <em>SHOREA</em> <em>CURTISII</em> (DIPTEROCARPACEAE): AN ASSESSMENT USING SSR AND DAMD MARKERS

Abstract

HO, W. S., WICKNESWARI, R., MAHANI, M. C. & SHUKOR, M. N. 2006. Comparative genetic diversity
studies of Shorea curtisii (Dipterocarpaceae): an assessment using SSR and DAMD markers. Genetic diversity
of Shorea curtisii from different age cohorts, namely, seedlings, saplings and adult trees were determined
using six SSR loci and 33 DAMD loci. To quantify genetic diversity in S. curtisii we used standard genetic
diversity measures for SSR data, and both phenotypic and genotypic methods with null-allele frequency
corrected for deviation from Hardy-Weinberg equilibrium (HWE) with SSR markers for DAMD data. Results
showed that the genetic diversity measured using DAMD genotypic method was lower than those derived
from SSR data based on the same set of samples. This suggests that DAMD allele frequencies corrected
from HWE deviation using fixation index derived from SSR data may be underestimated. The genetic
distance matrix generated from SSR data was significantly correlated with DAMD genotype data (r = 0.990,
p < 0.05), indicating a similar genetic structure of S. curtisii being depicted by both marker types among the
age cohorts tested. The relationship between sample size and genetic diversity measures demonstrated a
threshold level, i.e. n = 20 and n = 30 for seedlings and saplings respectively, and n = 15 and n = 20 for adult
trees revealed by SSR and DAMD markers respectively. Genetic diversity measures dropped drastically below
these levels. These results further imply that a highly heterogeneous population was observed in S. curtisii
from each age cohort. Collectively, both SSR and DAMD markers have good genome coverage in the S.
curtisii genome.