Microsporogenesis in Jatropha curcas L.

Jatropha curcas L. is an important oil crop for biofuel production. As such, the yield is commercially important and breeding programmes are focused to select and propagate high yielding individuals. Haploid plants are very useful in these programmes to produce true homozygotes in a short period of time. These lines may display a combination of new interesting agronomic traits and can be used to develop inbred cultivars and parental lines for F-1 hybrids. Few works have dealt with Jatropha curcas microsporogenesis, a crucial first step to study in vitro microspore embryogenesis. We have performed cytological, histological and scanning electron microscopy (SEM) analysis of Jatropha microsporogenesis. Microspores and pollen grain developmental stages were studied in relation to flower bud development. Attempts to achieve in vitro germination have also been carried out. Ten different developmental stages were established for male flower buds. Stages 3 and 4 are those that contain most uninucleate microspores. The pollen exine is very sculptured and no germination pores are visible on mature grains. Pollen grains germinated in media with high sucrose concentrations. Mature pollen grains were characterized by the presence of a large number of starch grains and lipid bodies. A low frequency of small pollen grains (4.7%) was observed among the J. curcas normal pollen. The size and weight of the pollen grains was estimated, which is relevant for the natural pollination process, and may help to design protocols for microspore isolation. In some species the isolated microspore cultures are the only way to induce pollen embryogenesis and in these cases no doubts exist about the origin of the embryos.