Genetic analysis of physic nut Jatropha curcas L. populations in Thailand using ISSR markers

Jatropha curcas L. (Physic nut) is a drought-resistant shrub belonged to the family Euphorbiaceae. The oil from most J. curcas varieties has a low viscosity that makes it an attractive alternative energy source for biofuel production. Evaluating the degree of genetic diversity between populations and the development of genome wide markers are important for the long-term improvement of cultured varieties in any given habitat. The genetic diversity of 58 samples from 13 J. curcas populations, and one outgroup of J. gossypifolia, in Thailand were analyzed by inter-simple sequence repeat (ISSR). From 12 screened ISSR primers, two primers ((AG)₈ T and (ATG)₅) generated a total of 21 discrete and reliably amplified products, of which 15 were polymorphic and revealed 71.4% polymorphism among the tested J. curcas in Thailand. An UPGMA dendrogram of the Thai J. curcas samples, based on their genetic similarity using these dominant ISSR markers, divided the 13 populations into at least six main groups, with two being further divided into at least two subgroups each, which were largely incongruent with their geographical locations. It is possible that the genetic variation within J. curcas, which is widely distributed throughout Thailand since its initial introduction, is caused by human disturbance.