Jatropha curcas (jatropha) is a potential biodiesel
crop. A major limitation in production is that
jatropha remains wild with low genetic variation. Related
species/genera in the Euphorbiaceae can potentially be used
for its genetic improvement. In this study, we employed
inter-simple sequence repeats (ISSRs) to assess genetic
variation among 30 accessions of jatropha, two accessions
of bellyache bush (Jatropha gossypifolia), two accessions
of spicy jatropha (Jatropha integerrima), two accessions of
bottleplant shrub (Jatropha podagrica), and three accessions
of castor bean hybrids. Genetic relationships were
evaluated using 27 of 86 ISSR markers, yielding 307
polymorphic bands with polymorphism contents ranging
from 0.76 to 0.95 for IMPN 1 and UBC 807 markers,
respectively. Dice’s genetic similarity coefficient ranged
from 0.39 to 0.99, which clearly separated the plant
samples into seven groups at the coefficient of 0.48. The
first group comprised J. curcas from Mexico, the second
group comprised J. curcas from China and Vietnam, the
third group comprised J. curcas from Thailand, the fourth
group was J. integerrima, the fifth group was J. gossypifolia,
the sixth group was J. podagrica, and the last and
most distinct group was Ricinus communis. Analysis of
molecular variance revealed that 63% of the variability was
attributable to variation among groups, while 37% was due
to variation within groups. Based on Nei’s genetic distance,
the population from G2 (J. curcas from China) and G4