Narrow genetic and apparent phenetic diversity in Jatropha curcas: initial success with generating low phorbol ester interspecific hybrids

Due to the increasing popularity of Jatropha curcas as a feedstock for biodiesel, generating non-toxic 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. However, 6 different species of Jatropha from India exhibited pronounced genetic diversity indicating possibilities of improving J. curcas by interspecific breeding. The relatively unexplored cTBP approach we used was a highly efficient and cost effective genotyping tool. Using such tools towards breeding J. curcas for low phorbol ester (PE) content is highly desirable because of the co-carcinogenic nature of the PEs present in all the commercially relevant parts such as seeds, seed-cake and biodiesel. We report initial success in obtaining interspecific F1 and back cross (BC1) plants with low PE and improved agronomic traits.Further efforts will lead to generating varieties with targeted traits. Despite the limited genetic diversity within J. curcas accessions, appreciable variability was noticed 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.