The 2012 ASHS Annual Conference

Jatropha (Jatropha curcas L.) is a species that has been identified for biodiesel and jet fuel production, as seeds produce oil of high quality.  However, because jatropha is non-domesticated, poor branching and high male to female flower ratio are limitations to achieving high yields at the commercial level. Plant growth regulators (PGRs) have been used to increase branching and yield in various species.  Therefore, PGR applications could promote increased flowering and potentially increased fruit production in jatropha. The objective of this study was to evaluate the effects of ethephon and a combination of 6-benzyladenine (BA) and gibberellic acid (GA_{4 +7}) on branch induction, and subsequent flowering and fruit production in jatropha.  A total of 32 actively growing plants (with leaves) and 32 dormant plants (without leaves) were entirely sprayed with single applications of either ethephon or BA + GA_{4 +7}. Final plant size, final number of branches per plant, total number of inflorescences per plant, inflorescence set, total number of fruits per plant, fruit yield (g), total number of seeds per plant, and seed yield (g) were recorded. Plants with leaves showed greater size, fruit yield, and seed yield as compared to plants without leaves. Although plants without leaves showed greater inflorescence set, no differences were found for the total number of inflorescences, and fruits and seeds per plant when compared to plants with leaves.  Plants without leaves showed no significant differences for growth, flower, fruit and seed parameters in response to ethephon or BA + GA_{4 +7} applications.  Plants with leaves showed no increase in the number of branches due to PGR applications. However, plants treated with BA + GA_{4 +7} showed greater growth index than plants treated with ethephon. There was no increase in the number of branches or in the number of inflorescences per plant. However, inflorescence set, number of fruits and seeds per plant, fruit yield and seed yield increased to a certain degree as concentration increased, then decreased as concentration decreased. The PGRs here examined appear to have a greater effect on fruit and seed production than on branching stimulation.  Multiple applications and higher concentrations might be required to promote branch induction in jatropha.