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In order to shorten generation cycles, a greenhouse strategy was used as control and compared with an in vitro plus in vivo strategy for pea and bambara groundnut, as well as to an in vitro only strategy for pea and grass pea. Using an in vitro plus in vivo system and embryo axis explants, nearly six generations per year for Pisum and over four generations for Vigna were obtained, compared with two generations in the field. Using successive generations from seed to seed in pea, the mean duration for one generation was 67.2 ± 4.6 days in ‘Frisson’, against a mean of 143 ± 3 days in the field. With the in vitro only strategy in pea, 6.87 generations per year were obtained with ‘Frisson’ and 5.24 with ‘Terese’, while with grass pea genotypes over three generations per year were possible. All plants obtained were morphologically normal and fertile. These results show the feasibility of using such strategies to reduce significantly the duration of generation cycles in legumes, thus offering novel approaches for breeding these important crops.

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The production of whole plants from explants of protein pea (Pisum sativum L.) using an efficient, reliable and rapid strategy, while maintaining trueness to type, will be required before regeneration can be exploited for genetic transformation. Seeds of the pea genotypes Terese, Solara, Frisson and P64 (a hypernodulating mutant line of Frisson) were surface-sterilized and imbibed overnight, whereafter embryo axes were dissected and germinated on hormone-free medium for 7-10 d. Hypocotyl sections lacking pre-existing meristems were harvested and cultured on a range of media with various concentrations and combinations of growth regulators in order to induce either caulogenesis or somatic embryogenesis. Differences in responsiveness were apparent between genotypes, but regeneration via caulogenesis was consistently more reliable than via the induction of somatic embryos. Few explants underwent somatic embryo production and their conversion into plants has remained elusive so far, irrespective of the genotype studied. Conversely, large numbers of buds were produced within 10 d by organogenesis, and healthy, rootable shoots were obtained. A clear relationship was observed between the growth regulators employed for bud regeneration and shoot rooting phases and the subsequent competence of the regenerated plants for flowering, pod formation and viable seed production.

No abstract