New microsatellite markers classifying nontoxic and toxic Jatropha curcas

Abstract

Jatropha curcas (jatropha) (2n = 2x = 22) is a shrub originated from Central America and spread to Africa and Asia by Portuguese traders during 18th century. This species belongs to the family Euphorbiaceae. Jatropha seed is high in oil content and considered promising as an alternative renewable and eco-friendly energy source, especially for biodiesel. Most jatropha accessions are high in seed phorbol ester (PE), a tumour inducing substance and thus called toxic accessions. There are some low PE (nontoxic) accessions in Mexico that are locally consumed as snack foods or sweets. The toxic and nontoxic accessions cannot be distinguished morphologically (Ghosh et al. 2007; Makkar et al. 2008), thus the villagers vegetatively propagate them to avoid contamination of high PE character. Currently, the only way to identify the high and low PE seeds is by seed analysis with high performance liquid chromatography (HPLC). Jatropha breeders are looking for a cheaper and quicker way to distinguish them such as through molecular markers, provided that the location(s) of gene(s) controlling high PE content is known. To achieve this, a number of markers are required to cover all the 11 linkage groups. Basha and Sujatha (2007) reported that among 400 RAPD primers tested, 339 produced bands and 267 were polymorphic. They also tested a set of 207 ISSR primers and found that 100 of them produced bands, giving 29 polymorphic primers. They used this information to investigate genetic variation among 42 accessions of jatropha from India and a nontoxic accession from Mexico. Basha and Sujatha (2009) reported genetic variation and interspecific hybrids of Jatropha species using RAPD and ISSR as nuclear specific markers, and chloroplast microsatellite markers as organelle specific markers. Ganesh et al. (2008) studied genetic diversity of eight Jatropha species collected in India. Eighteen of 26 RAPD primers classified them into a group of J. curcas versus a group of other seven Jatropha spp. Gupta et al. (2008)