Biodiversity and indigenous management of the endangered non-toxic germplasm of Jatropha curcas L. in the Totonacapan (Mexico), and the implications for its conservation

Mexico is a center of diversity of Jatropha curcas. Worldwide there are two groups of germplasm, the toxic and the non-toxic, and most of the biofuels programs are based on toxic germplasm. In the mountains of the Totonacapan (Mexico), non-toxic genotypes have been cultivated for human food from ancient times, and now they are in serious risk of being lost because of the "biofuel program'', as well as the ethnobotanical knowledge about this germplasm in the Totonaca culture. The starting hypothesis is that this ethnobotanical knowledge must be related with a high biodiversity of the germplasm of this crop, which is necessary to preserve to avoid genetic erosion. The objective of the work was to assess the biodiversity of the native germplasm using morphological traits, and to analyse socio-economic aspects related with the ethnobotany of this germplasm, to design strategies for the conservation of the germplasm and of the culture linked to it. Other specific objective was to select morphological variables highly discriminant and easy-to-measure, for the characterization of this crop. We selected eight morphological descriptors as the most discriminant, related with the leaves: Length and width of the blade, and length of the petiole; and the fruit: weight, length, diameter, length of the peduncle, and number of fruits per bunch. On the basis of the principal component analysis and canonical discriminant analysis of the morphological data, it was possible to identify as different germplasm pools the six locations sampled, in spite of their proximity, confirming the starting hypothesis that there is high biodiversity of this crop in the region. The pools from Camocuautla and Tuzamapan were the most similar between them, with small fruits and a low number of teeth in the leaves. The germplasm form Jonotla showed also small fruits, but small leaves and a short petiole. Tetelilla's germplasm showed a high number of teeth in the leaves, big fruits and leaves, and long petiole. The accessions from Ecatlan showed big fruits, low number of fruits per bunch and short fruit's peduncle, with small leaves and a short petiole. The differential traits of the accession from Zozocolco were a high number of fruits per bunch and a long fruit's peduncle. Unlike what happened with the germplasm, the socio-economic profile of the farmers did not follow a geographical pattern. Facing the scenario of establishment of the "biofuel program'' in the region, we proposed an on farm conservation strategy consisting in the exclusive use of local nontoxic germplasm, which will need the involvement of all the stakeholders, and in special of the local plant nurseries. As this is difficult to achieve, the ex situ conservation has been proposed as an emergency action. Even if the genetic erosion is stopped, it is necessary to develop other companion measures to avoid the loss of the knowledge about the ancestral uses of this crop, as the farmers could prefer to sell the crop for the industry, instead of use at least a part of it for their own food