Transformation efficiency depending on the phenotype of maintained embryogenic callus cultures. Transformation efficiency was assessed by observing GFP epifluorescence 6 weeks after the end of co-cultivation. Transformation efficiency was estimated by the proportion (p) of transformed calli (p = x/n), where x is the number of transformed calli and n the number of co-cultivated calli. A 3 δ confidence limit for binomial distribution was calculated using the formula with a level of confidence of 99%. Confidence interval is indicated by vertical bars. For each callus phenotype, all the transformation experiments were conducted independently in three replicates comprising 40 calli (120 calli/phenotype).