Submitted to: Alfalfa Improvement Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: June 17, 1996
Publication Date: N/A
Technical Abstract: A highly efficient transformation system based on cocultivation of leaf explants with Agrobacterium tumefaciens was developed for a clone selected from the alfalfa variety Regen SY. Plants were selected for rapid regeneration in tissue culture and susceptibility to transformation by A. tumefaciens. Three different commonly used disarmed strains of A. tumefaciens were tested: LBA4404, AGL-1, and ABI. The efficiency of transformation was highly dependent on the strain used. No transformed embryos were produced with strain ABI, a moderate number were obtained using AGL-1, while high numbers of transformed embryos were produced using LBA4404. Extensive explant necrosis was often observed when using strains AGL-1 and ABI. The optimal length of cocultivation using strain LBA4404 was 7 days. Plants are transferred to soil 9 to 12 weeks after cocultivation. Susceptibility of intact plants to tumorigenesis by wild type strains of A. .tumefaciens was highly correlated with dormancy. The strong correlation between dormancy and resistance to oncogenic strains was not observed with disarmed strains. However, for most germplasms, there was a strong germplasm-strain interaction. More individual plants were transformed by strain LBA4404 than with AGL-1 or ABI. The alfalfa transformation system has been used to analyze the expression patterns of alfalfa promoters, to identify elements required for expression in nodules, and for antisense RNA expression. The system is currently being used to engineer alfalfa for bioremediation and for increased leaf retention.