Abstract

Andrographis paniculata (Burm. f.) Nees is a medicinal plant widely used in Thailand and many countries for therapeutic value. The present study was aimed to investigate its genotypic variations in various locations of Thailand based on simple sequence repeats (SSR), amplified fragment length polymorphism (AFLP) and random amplified polymorphic dna (RAPD) marker system. SSR, AFLP and RAPD were compared in terms of their informativeness and efficiency in a study of genentic diversity and relationships among 58 samples of A. paniculata in Thailand. All three techniques presented highly correlated results, with a correlation coefficient of r = 0.996. The low values of expected heterozygosity were obtained for all marker systems due to their capacity to reveal the low number of polymorphic bands in each markers system. All marker systems also gave very high genetic similarity values, which represent the values that are higher than 0.9; the highest is SSR (0.989) followed by AFLP (0.964) and RAPD (0.905), respectively. The cophenetic correlation coefficients of similarity were statistically significant (r = 0.996, p < 0.001) thus implying the correspondence for all combination of three marker systems. The results obtained indicated that the distribution of A. paniculata among each region of Thailand are likely to belong to the same variety and are relatively undifferentiated across a large geographic rang.

Key words: Andrographis paniculata, SSR, AFLP, RAPD, genetic similarities.