Chiang Mai Journal of Science

Jatropha curcas L. has been considered a potential source of biodiesel feedstock due to its high seed oil content. However, Jatropha exhibits low numbers of female flowers leading to insufficient seed yields for biodiesel production. The application of paclobutrazol (PCB) on various types of plants, including Jatropha, has been reported to increase female flower numbers. Nevertheless, the underlying molecular mechanism remains unclear. This study investigated the effects of PCB on inflorescence physiology and expression of floral development-related genes. Apparently, PCB significantly decreased inflorescence size, pedicel numbers, pedicel length, and the distance between the inflorescence’s internodes. These physiological changes might result from the effect of PCB on inhibiting gibberellin synthesis genes, including Ent-kaurene oxidase (JcKO), Ent-kuarene synthase (JcKS), GA20 oxidase1 (JcGA20ox1), and RGA-LIKE (JcRGL). Moreover, PCB significantly reduced the number of male flowers, whereas the number of female flowers was increased. The alteration in flower numbers of Jatropha might be due to the up-regulation of CYTOKININOXIDASE/DE HYDROGENASE (JcCKX1 and JcCKX5) and CRYPTOCHROME CIRCADIAN CLOCK 2 (JcCRY2) expression. To validate the function of these genes, further study via genetic modification would be required.