Molecular markers reveal limited genetic diversity in a large germplasm collection of the biofuel crop Jatropha curcas L. in Brazil

The genetic diversity of a comprehensive germplasm collection involving 192 Jatropha curcas L. accessions collected throughout Brazil, spanning a wide latitudinal range from the states of Maranhao (1[degrees]49' S, 44[degrees]52' W) to Rio Grande do Sul (29[degrees]33' S, 55[degrees]07' W), was studied with 96 random amplified polymorphic DNA (RAPD) primers and six selected microsatellite markers. Only 23 of the 381 replicated RAPD markers and one microsatellite were polymorphic. Surprisingly, all accessions were homozygous at all but one microsatellite, in contrast with the outcrossing mating system reported for the species, suggesting that J. curcas not only supports selfing but possibly breeds by geitonogamy. Similarity based clustering revealed only 43 unique multilocus profiles in the 192 accessions. The probabilities of accessions with indistinguishable multilocus profiles being true duplicates varied between 83 and 99%. No relationship between clustering of accessions and geographic origin was observed, suggesting that J. curcas has experienced a widespread dispersion across regions by seeds and possibly vegetative propagules. The narrow genetic base and extent of potentially duplicated accessions likely reflects a recent common ancestry, drift, and intensive selection of the currently cultivated materials since the time of introduction. This result highlights an urgent need for the introduction of new and diverse accessions to this germplasm collection if Brazil is to drive and sustain successful breeding programs. doi: 10.2135/cropsci2010.02.0112