Isozyme polymorphism in Curcuma alismatifolia Gagnep. (Zingiberaceae) populations from Thailand

Abstract

Over-collection of Curcuma alismatifolia Gagnep. and habitat destruction had greatly reduced the number of individuals in their natural habitat resulting in genetic erosion. We conducted the isozyme analyses to reveal the genetic diversity among natural populations compared with the cultivated populations. Out of seven enzyme systems analyzed in this study, five enzymes (ADH, GDH-1, LAP-1, GPI-2, PGM) which gave reproducible and consistent bands were used; DIA and EST were excluded due to their complex and inconsistent bands. The GPI-2 loci showed the most variable with six allozymes and 10 zymogram patterns followed by GDH-1 with 5 and 5, ADH with 3 and 5, PGM with 4 and 4, and LAP-1 with three allozymes and four zymogram patterns. Cultivated populations from Japan (cJ) and Thailand (cT) had the lowest percentage of polymorphic loci ( P=40–60%), alleles per locus ( A l=1.8), alleles per polymorphic locus ( A p=2.33–3.00), and gene diversity ( H s=0.216–0.304) compared with two lowland populations (L1, L2) with P=100%, A l=3.0–3.2, A p=3.0–3.2, H s=0.465–0.496; and six highland populations (H1–H6) with P=80–100%, A l=2.4–3.8, A p=2.4–3.8, H s=0.342–0.659. Within population, H1 (the highest elevation sampled in this study) had the greatest genetic diversity ( H s=0.659). Mean genetic diversity over all loci across all populations was 0.444. Mean genetic identity between cultivated populations ( I C), lowland populations ( I L), among highland populations ( I H), and across all populations ( I SP) were 0.950, 0.947, 0.944, and 0.922, respectively. Using UPGMA cluster analysis, H1 and cJ were separated first from the rest into distinct groups. Two lowland populations were placed together with H6, while cT was grouped in the same cluster of H2–H5.