SUSCEPTIBILITY OF COMMON AND TEPARY BEANS TO AGROBACTERIUM SPP STRAINS AND IMPROVEMENT OF AGROBACTERIUM-MEDIATED TRANSFORMATION USING MICROPROJECTILE BOMBARDMENT

To develop an efficient protocol for Agrobacterium-mediated transforma tion of common bean (Phaseolus vulgaris L.) and tepary bean (P. acutif olius A. Gray), we have tested the susceptibility of six genotypes to eight Agrobacterium tumefaciens and two A. rhizogenes strains, The vir ulence of the Agrobacterium strains was shown to be genotype dependent . In general, the tumors observed on common bean cultivars were larger than those observed on tepary bean cultivars. The A. tumefaciens AT81 96 and Ach5 strains and the A, rhizogenes 8196 strain induced the best responses in all genotypes tested, Polymerase chain reaction (PCR) an alysis confirmed the presence of T-DNA in tumors derived from inoculat ion with three A. tumefaciens strains in common beans, Apical meristem s of P. vulgaris cv. Jalo were bombarded with tungsten microprojectile s and then inoculated with an A. tumefaciens wild-type strain (Ach5), One month later, the explants showed a high frequency of tumor formati on (50% to 70%), Similarly, when bombarded meristems were inoculated w ith an A, tumefaciens disarmed strain (LBA4404/p35SGUSINT), 44% of the m showed substantial sectors of GUS activity, suggesting the expressio n of introduced gene. The bombardment/Agrobacterium system appears to be a promising method to stably transform bean through the regeneratio n of plants directly from transformed apical meristems.