STUDY ON GENETIC CONTROL FOR PHORBOL ESTERS ACCUMULATION IN JATROPHA CURCAS GENOTYPES

Aims: To obtain information on the genetic control of phorbol esters (PE) biosynthesis in J. curcas. A valorization of byproducts after oil extraction could contribute to a significant improvement in the economic sustainability of this new biofuel crop, but its use as animal feed is currently prevented by the presence of toxic PE.
Study Design: Direct and reciprocal crosses between toxic and non-toxic genotypes.
Place and Duration of Study: Ghana, Mexico and Italy, between 2010-2013.
Methodology: Two toxic genotypes from Africa and South America and two non-toxic genotypes from Mexico were used in the study as parental lines. The four genotypes were selected after analysis for complete homozygosis at 5 Simple Sequence Repeats (SSR) loci.
The toxic genotypes were direct and reciprocal crossed with non-toxic genotypes to obtain six F1 populations and two F2 populations. The hybrid nature of F1 seeds and the genetic segregation of F2 were analysed with SSR markers. Parental, F1 and F2 seeds were individually analyzed for the whole PE content in the kernel.
Results: The set of markers has allowed the true hybrid nature to be confirmed for all crosses between toxic and non-toxic genotypes because the individuals were heterozygous at all loci. In the direct crosses between a toxic seed-bearing plant with a non-toxic pollinator all F1 seeds were toxic. Conversely, in the corresponding reciprocal crosses, all the seeds were non-toxic. These results show that in each case PE content in F1 seeds of J. curcas depends on the maternal phenotype and F2 seeds did not segregate for toxicity as expected for a trait under maternal control.
Conclusion: The results of this work pointed out a maternal effect on the synthesis of the PE in the seeds of J. curcas and probably the tegument, tissue of maternal origin, contributes most to the PE content.