Genome size, base composition and karyotype of Jatropha curcas L., an important biofuel plant Carlos Roberto Carvalho a , Wellington Ronildo Clarindo a , Milene Miranda Prac ¸a a , Fernanda Santos Arau ´ jo a , Nicolas Carels b,c, * a Universidade Federal de Vic ¸osa (UFV), Laborato ´rio de Citogene ´tica e Citometria, Vic ¸osa, MG, Brazil b Universidade Estadual de Santa Cruz (UESC), Nu ´cleo de Biologia Computacional e Gesta ˜o de Informac ¸o˜esBiotecnolo ´gicas, Ilhe ´us, BA, Brazil c Fundac ¸a ˜o Oswaldo Cruz (FIOCRUZ), Instituto Oswaldo Cruz (IOC), Laborato ´rio de Genoˆmica Funcional e Bioinforma ´tica, Rio de Janeiro, RJ, Brazil 1. Introduction Jatropha curcas (Euphorbiaceae) or simply Jatropha (also known as Pinha ˜o-Manso in Portuguese), is a tree thought to be native from Central America [1] and possibly from Brazil. It is now almost pantropical and has been listed as a weed in Australia, South Africa, India, Brazil, Fiji, Honduras, Panama, El Salvador, Jamaica, Puerto Rico, and other parts of Caribbean. There is growing interest in the use of J. curcas oil to alleviate the energy crisis. J. curcas oil is relatively simple to convert to biodiesel by chemical [2] or biological transesterification [3]. In addition to the low production cost, J. curcas biofuel has been reported to be non-toxic, clean and eco-friendly [4]. This euphorbia is a ‘‘drought resistant’’ plant which grows on wasteland and could easily be cultivated by low income farmers. It is grown as a shrub and thought that it could benefit energy provision to remote areas. In this respect, J. curcas is considered a strategic crop for countries such as Brazil or India. After irrigation, fertilization and soil tillage, J. curcas may reach the flowering stage within 1 year of planting and produce an abundant crop. Although it may look promising, it lacks an improved germplasm. Consequently, several pests and diseases have already been observed at the industrial production level. (personal communication from Nagashi Tominaga, NNE Minas Agro Florestal ltda, Brazil). In addition, the J. curcas oilcake is not suitable for feeding livestock because of toxic compounds such as phorbol ester and curcin [5–9]. While J. curcas germplasm is being harvested all over the world with the purpose of crop improvement, little is known about its genome. In this study, we measured the genome size and base composition of J. curcas by flow cytometry and mounted its karyotype from root-tip chromosomes. 2. Materials and methods 2.1. Plant material J. curcas seeds from the progenitor ‘Gonc ¸alo’ were kindly provided by Nagashi Tominaga (NNE Minas Agro Florestal Ltda, Janau ´ ba, MG, Brazil). Seeds of Raphanus sativus ‘Saxa’ with 2C = 1.11 pg [10] and GC = 38.6% [11] were gently supplied by Jaroslav Dolez ˇel (Experimental Institute of Botany, Czech Repub- lic). Seeds were germinated at 30 8C and plantlets were grown in a greenhouse at 25 8C. Plant Science 174 (2008) 613–617 ARTICLE INFO Article history: Received 8 January 2008 Received in revised form 17 March 2008 Accepted 19 March 2008 Available online 26 March 2008 Keywords: 2C DNA content Base composition Biofuel plant Flow cytometry Karyotype Jatropha curcas ABSTRACT In this report, we present the genome size, the base composition and the karyotype of Jatropha curcas L., which is becoming an important oleaginous crop in tropical areas for biofuel production. The genome size and the base composition were obtained by flow cytometry of G 0 /G 1 nuclei stained with propidium iodide (for genome size), DAPI (for AT) and chromomycin A3 (for GC), respectively. The karyotype was obtained by root-tip (i) incubation with amiprophos-methyl (microtubule inhibitor), (ii) digestion in enzymatic solution, (iii) squashing on glass slides, (iv) fixation and (v) coloration in Giemsa solution. We found that the genome of J. curcas is relatively small and in the same size range as that of rice. The flow cytometry indicates an average 2C value of 0.85 pg and an average base composition of 38.7% GC. The karyotype of J. curcas is made up of 22 relatively small metacentric and submetacentric chromosomes whose size range from 1.71 to 1.24 mm. The possibility of a polyploidization event in the evolutionary history of J. curcas is discussed. ß 2008 Elsevier Ireland Ltd. All rights reserved. * Corresponding author at: Fundac ¸a ˜o Oswaldo Cruz (FIOCRUZ), Instituto Oswaldo Cruz (IOC), Laborato ´ rio de Geno ˆmica Funcional e Bioinforma ´ tica, Rio de Janeiro, RJ, Brazil. E-mail address: nicolas.carels@gmail.com (N. Carels). Contents lists available at ScienceDirect Plant Science journal homepage: www.elsevier.com/locate/plantsci 0168-9452/$ – see front matter ß 2008 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.plantsci.2008.03.010