Intergeneric hybridization between Jatropha curcas L. and Ricinus communis L., through in vivo and in vitro pollination techniques

Abstract

Jatropha curcas (2n= 2x=22) and R. communis (2n=2x=20) are becoming commercially important plant species as their oil rich seeds can be processed into a substitute for diesel. Hybridization between R. communis and J. curcas could potentially produces the hybrid with characteristic such as short plant type, early maturity, determinate inflorescence, high oil quality and productivity/year competitive with oil palm. The pollen grain of J. curcas (96 μm) was 3 times bigger than R. communis (32 μm). Jatropha curcas was introduced as the female parent plant as determined by pollen grains and ovule size. The in vivo pollination test resulted 100% of flowers in the field being aborted within an average of 10 days after pollination. Pollen germination and normal growth of the pollen tube were observed in 48 h after pollination but failed to set the seed more than 2 weeks. This indicates that the in vivo pollination was due to a lack of pre-zygotic barrier. In vitro pollination with cultures in MS medium and the addition of 0.125 mg L-1 benzyladenine (BA), singly or combined with 0.125 mg L-1 1- naphthaleneaceticacid (NAA) can prolong the zygote life for up to 57 days. This study showed the in vitro techniques may provide a feasible method in order to obtain new intergeneric plants. Additionally, the oil content of J. curcas showed the strong correlation with the seed weight. However, negative correlation was observed in R. communis. The commercial R. communis with a small seed size has higher oil content than the wild-type. The percentage of oil content of J. curcas toxic, J. curcas nontoxic, R. communis commercial and R. communis wild- type (A) was 53.03%, 39.47%, 27.03% and 23.25%, respectively. Oleic acid (39-40%) and linoleic acid (35-37%) were predominant of the fatty acid composition in J. curcas. Ricinus communis wild-type (A) showed higher ricinoleic acid (89%) than the commercial type (79%).