The 2012 ASHS Annual Conference

Biofuels and bioenergy encompass a wide range of alternative sources of energy of biological origin.  Jatropha (Jatropha curcas L.) has become a species of interest worldwide because its seeds produce oil of high quality for biodiesel and jet fuel. However, the species agronomical characteristics and the potential seed production is still uncertain, as research programs in jatropha are very limited.  Jatropha flowers are unisexual, monoecious, and cross-pollination is performed by insects. Under normal circumstances, jatropha shows protandry, whereby male flowers start opening from the first or second day of the inflorescence life (13–19 days), while female flowers open later, with 60% opening from the third to the fifth day.  Therefore, the opening mechanism of female flowers in jatropha promotes out crossing and minimizes self-pollination.   However, many studies have reported that this species is self-compatible with high fruit set percentages.  Furthermore, jatropha is also capable of reproduction through apomixis.  The objectives of this work were to assess pollen viability and fruit set during three seasons and to elucidate the pollination mechanisms in 17 jatropha accessions growing in South Florida.  Pollination and fertilization are influenced by pollen deposition on stigma, nectar availability and pollen viability, which is strongly influenced by temperature, moisture and genotypic differences. In this study, the number of female flowers per inflorescence, male:female flower ratio, and fruit set were evaluated using four replications per accession.   Fruit fresh weight, number of seeds per fruit, seed fresh and dry weight, and oil content were evaluated using 30 replications per accession.  Data was submitted to analysis of variance.  The number of female flowers per inflorescence, male:female flower ration, and fruit set were significantly influenced by seasonal changes and genotype for eight, four, and six accessions, respectively.  Pollen germination percentage was also affected by the season and genotype, whereby 14 accessions had higher germination during summer, from which 8 accessions maintained higher germination percentage during dall.  Seed characteristics were also significantly different as influenced by pollination mechanisms