Expression of the bar gene confers herbicide resistance in transgenic lettuce

Resistance to bialaphos, a broad-spectrum herbicide, was introduced into La ctuca sativa cv. Evola by Agrobacterium tumefaciens-mediated transformation . A. tumefaciens strains 0310 and 1310, both carrying the bialaphos resista nce (bar) and neomycin phosphotransferase (nptII) genes, were used for tran sformation. Primary transformants were selected on kanamycin sulphate-suppl emented shoot regeneration medium. Integration of both transgenes was confi rmed by non-radioactive Southern hybridisation. The hypervirulent plasmid T oK47 in A. tumefaciens strain 1310 generated multiple insertions of T-DNA i n some transgenic plants; the absence of pToK47 (strain 0310) resulted in s ingle gene inserts in all plants tested. Resistance to glufosinate ammonium was observed in axenic seedlings grown on medium supplemented with the her bicide at 5 mgl(-1) and in glasshouse-grown plants sprayed with the compoun d at 300 mg l(-1). Stable expression of the bar gene was observed in R2 gen eration plants. The kanamycin resistance of R1 seedlings was observed by ge rminating seeds on medium supplemented with 200 mg l(-1) kanamycin sulphate . The presence of NPTII protein and PAT enzyme activity were demonstrated b y ELISA and PAT enzyme assay respectively. Transgenes segregated in a Mende lian fashion in some plant lines in the R1 generation; herbicide resistance also segregated in the expected ratio in the R2 generation in most transge nic lines. This study confirmed that an agronomically important transgene c an be integrated and stably expressed over several generations in lettuce.