Phenotypic and genotypic variability were evaluated in a population of 227 F2 plants
derived from an interspecific cross between Jatropha curcas (cv. “Chai Nat”) and Jatropha
integerrima (local dwarf ornamental type) from Thailand. The objective of this study was to
assess the range of variability for 13 phenotypic characters and 16 EST-SSR markers
observed in the population. A high variation was found in morphological characters
showing many superior genotypes over the J. curcas parent. The results of molecular parameters
also suggested a high level of genetic variability in the current population with
100% of polymorphic loci (PPL) for all 16 SSR primers used. The mean numbers of observed
alleles (Na) and effective alleles (Ne) were 2.13 and 1.81, respectively. The polymorphic
information index (PIC) ranged from 0.17 to 0.55 with an average of 0.34. The average values
of Nei’s genetic diversity (He), observed heterozygosity (Ho), and Shannon’s information
index (I) were 0.43, 0.47, and 0.64, respectively. Jaccard’s similarity coefficient ranged from
0.51 to 0.96 with a continuous distribution. The UPGMA-based dendrogram could not
classify the F2 plants into clusters, but separated them into three sub-groups and seven
distinct plants at 61% similarity. The information generated from the current research will
be of great benefit to jatropha breeding program; providing a new gene source to the
currently low variation in J. curcas.