Efficient regeneration systems for two closely related Moricandia species possessing a C3 or C3-C4 intermediate photosynthetic character.

The C(3)-C(4) intermediate species Moricandia arvensis ( Brassicaceae) and its closest C(3) relative, Moricandia moricandioides, represent model species for studying the C(3)-C(4) photosynthetic character relative to the C(3) phenotype. In order to enable transgenic analyses in these two species, optimal regeneration systems based on leaf and/or stem internode segments were developed, and genotypes suitable for in vitro tissue culture were identified. Evaluation of the regeneration capability of 30 M. arvensis genotypes and 12 M. moricandioides genotypes revealed that all could form callus. However, shoots were only produced by 40% of the M. arvensis genotypes and 8% of the M. moricandioides genotypes. The two Moricandia species showed significant genotypic differences with respect to callus formation and shoot regeneration. For the 12 regenerative M. arvensis genotypes, 29-100% of the explants developed shoots, while 71% of the explants from the single regenerable M. moricandioides genotype formed shoots. The genotype used, the choice of stem or leaf explants and the composition of the medium (i.e. concentrations of different hormones and salts) significantly affected plant regeneration (chi-square analyses, P<0.05). Whole plants could be obtained in the greenhouse after 3-3.5 months for M. arvensis genotypes and after 4-4.5 months for M. moricandioides.