Abstract
Jatropha curcas is considered to be one of the greatest potential biofuel plants. However, the application of J. curcas is limited by a lack of high yielding varieties. Polyploids often generate useful germplasm for genetic improvement in many plants. Here, tetraploid and octoploid J. curcas were obtained by treating the shoot tips of seedlings with colchicine. The ploidy of J. curcas was determined by measuring the nuclear DNA content with flow cytometry and by counting chromosomes. Treatment with 0.1% colchicine for seven days was the most effective condition for producing polyploid plants, yielding 15% tetraploids. There was no significant plant height difference between tetraploid and diploid plants, but octoploid plants grew slowly and were about one-third the height of diploid plants. With increased ploidy, the stomata and pollen grains became larger, stomatal density decreased, the leaves became thicker, and the net photosynthetic rate and stomatal conductance decreased. Compared with diploid plants, the tetraploid plants had larger leaves, male and female flowers and pollen, but the octoploid leaves were about half the size of the diploid leaves. The fruits and seeds of the tetraploid plants were larger than those of the diploid, but the single seed weight and oil content were decreased. The octoploid plants were sterile, with no flower buds on three-year-old plants. The polyploid plants obtained in this study could be useful for breeding programs and for studies of flower development and abiotic stress tolerance in J. curcas.