Mutation breeding in the cat and dwarf date palms

In Costa Rica, the cat palm (Chamaedorea cataractarum) and the dwarf date palm (Phoenix roebelenii) are two popular ornamental cut-leaf crops. These two crops are easy to grow and maintain and produce leaves almost year-round. However, the absence of genetic diversity and plant breeding programs means that growers continue to offer the same product and are forced to compete for ever-diminishing prices. In this project we explored the possibility of exposing the fresh seed to two different mutagens, the alkylating agent ethyl-methyl sulfonate (EMS) and gamma-rays with a Cobalt-60 source. Germination tests suggest that in cat palm the median lethal dose (LD50) was 2 M for EMS (1/2 h) and between 20 and 50 Gy for gamma-radiation (n=75, three replicates). One year after irradiation with the LD50 survival was 10%. In the case of the dwarf date palm, the LD50 was 0.1 M for EMS (1/2 h) and 50 Gy for gamma-radiation. Two years after irradiation at 50 Gy survival was only 18%. It was possible to identify four likely cat palm EMS mutants, with apparent differences in leaf thickness and size. Nonetheless, these seedlings might be genetically unstable, thus the plants are being grown to harvest seed (M2 generation). Our results suggest that EMS mutagenesis is a feasible approach to breeding new cat palm cultivars without the need for tissue culture.