Overcoming crossing barriers between jatropha (Jatropha curcas L.) and castor bean (Ricinus communisL.)

Abstract A limitation in improvement of jatropha (Jatropha curcas) has been the low genetic variation among the available germplasm. An alternative to create genetic variability and incorporate desirable traits is through wide crossing. Due to reproductive barriers, wide crossing in jatropha has had limited success. In this experiment, intergeneric hybridization between jatropha and castor bean (Ricinus communis) was performed. In both direct and reciprocal crosses, a few stigma-compatible pollen grains were found. The pollen tube grew normally and reached the style base within an hour after pollination, but the embryo aborted a few days later. This indicated that the hybridization barrier was post-fertilization and thus the ovules were excised, cultured in MS medium supplemented with 1 mg L-1 IAA, and subcultured every four weeks. Finally we obtained one intergeneric hybrid plant, which was vegetatively propagated for further study.