Genetic diversity of Jatropha curcas in southern Mexico

Abstract

The importance of the Euphorbiaceous plant Jatropha curcas L. lies in its high-quality seed oil, ideal for the manufacture of biodiesel. As a result, its extensive cultivation has already reached several million hectares in Asia, Africa and Latin America, and implies certain challenges since it is not yet a fully domesticated plant, and with limited information on the agronomic processes and selected varieties for its cultivation. In addition, little is known about the biology, ecology, genetic diversity and geographic origin of its populations. Despite the growing body of knowledge on J. curcas, there are only a few studies on phenotypic and genotypic diversity in populations of Mexico, from where it is probably native. The greatest extension of J. curcas sown in Mexico is located in the state of Chiapas, for that reason this chapter describes diversity of populations of this state and other sites in Southern Mexico. To broadly understand the diversity of populations, our group has used two types of markers: Direct adaptive value characteristics, such as floral characters and fatty acids in the seed, and neutral molecular markers such as AFLP and microsatellites. The results of the chemical studies showed that the content of seed oil in accessions ranged from 8.02 % to 54.28 %, with the proportion of unsaturated fatty acids varying from 74.5 % to 83.7 %. A discriminant analysis separated populations according to their geographical origin, which was verified with a Mantel test. Using the Monmonier’s algorithm, two genetic barriers were identified between the populations. The results are discussed according to the putative evolutionary significance of the seeds fatty acid composition for this tropical species. Studies on floral anatomy confirmed a large variation among Mexican J. curcas and revealed the existence of plants exclusively with female inflorescences, which could be useful in the development of future plantations. Molecular studies showed that Mexican J. curcas is moderately structured in subpopulations, but with a high diversity within populations. A conglomerate analysis revealed the highest coefficient of dissimilarity based on accessions reported so far. The existence of genetic barriers isolating some populations was confirmed with molecular data. The results are discussed with reference to the possible ancestry of the populations. Finally, we highlight the relevance of some of our findings in the scientific and productive realms.