Efficient in vitro shoot regeneration responses of Phaseolus vulgaris and P-coccineus

Phaseolus vulgaris L. is the most important economic species within the genus Phaseolus, and it is grown in all parts of the world. Genetic improvement by conventional breeding has met considerable success, although production of hybrids between species within the genus has been limited due to sexual incompatibility or other evolutionary lethalities. Recent advances in tissue culture have offered the opportunity to produce cultivars which could not be obtained by conventional breeding methods, but regeneration protocols are influenced by the genotype. A standard regeneration procedure was assessed for its applicability to elite breeding lines of P. vulgaris L. and landraces of P. coccineus L. from seedling explants containing a cotyledon and a small portion of the split embryonic axis. In vitro culture response and regeneration ability varied significantly between species and amongst genotypes. P. coccineus produced more shoots per explant with a higher rooting efficiency than P. vulgaris. These significant genotype effects suggest that genetic factors are important in the response to in vitro tissue culture. Different genotypes were identified, which were more competent to in vitro culture and could produce highly responsible hybrids. This in vitro culture system carry a high potential for propagation of P. vulgaris and P. coccineus, and subsequent exploitation of hybrid forms, which could also be incorporated into somatic cell approaches to improve these species.