Factors affecting genetic and seed yield variability of Jatropha curcas (L.) across the globe: A review

Jatropha curcas L. is considered a promising candidate plant for biofuel production. However, data on its seed yield seem to vary greatly in different parts of the globe. Some studies indicate that low genetic diversity might be an important factor causing seed yield variation. In addition to genetic factors, abiotic factors such as rainfall or agronomic practices (e.g. planting density) may influence seed yield. Our study focused on reviewing current data on genetic diversity and other factors behind seed yield variability of J. curcas in different parts of its range, including areas both in its native and non-native range. Genetic and seed yield data were collected from published and unpublished documents available online. Our review shows that genetic diversity is significantly higher within its native range than in areas where the species has been introduced. Genetic diversity had a significant positive correlation with the mean annual seed yield. Seed yield varied greatly across the globe. Global mean (±SE) seed yield was 2218±148kgha−1y−1. Age of the plants had positive linear effects, whereas annual rainfall and plant density had quadratic effects on seed yield at global scale. The reported low genetic diversity in the non-native range of J. curcas may be explained by a low number of common ancestors and the resulting founder effect. The large variability in seed yields across the globe is probably caused by differences in plant age, varying agronomic practices, site specific climates, soil fertility and genetic factors. Although in a large proportion of Jatropha plantations worldwide the threshold level for economically feasible seed yield (2500kgha−1y−1 or more) may not be achieved, other benefits provided by Jatropha (e.g. carbon sequestration, erosion control) may support its cultivation even on arid or semi-arid sites.