Narrow genetic diversity in Jatropha curcas: initial success in generating low phorbol ester inter-specific hybrids

Due to the increasing popularity of Jatropha curcas as a feedstock for biodiesel, generating, nontoxic and high yielding varieties of the plant requires genotypic characterization towards identifying breeding lines. There is little information on the phylogenetic relationships between its global accessions and species. Assessing genetic variation by RAPD, AFLP and combinatorial tubulin based polymorphism (cTBP) in 38 J. curcas accessions from 13 countries on 3 continents revealed narrow genetic diversity while the 6 Jatropha species from India exhibited pronounced genetic diversity indicating higher possibilities of improving J. curcas by interspecific breeding. The relatively unexplored cTBP approach was an efficient molecular tool. Presence of the cocarcinogenic phorbol esters (PE) in the seeds, seed-cake and biodiesel is undesirable. We report initial success in obtaining interspecific F1 and back cross (BC1) plants with low PE and improved agronomic traits. Further BC populations will lead to varieties with targeted traits. Despite the limited genetic diversity within J. curcas accessions, appreciable variability exists in important phenotypic, physiological and biochemical traits such as seed size, water use efficiency and seed oil content respectively. This implicates fundamental epigenetic regulatory mechanisms and posits J. curcas as a unique system to study them.