A method is disclosed for making more efficient the particle-mediated germ line genetic transformation of bean species such as soybean. After a particle-mediated transformation event, in the absence of a selectable marker gene, relatively large numbers of plants must be regenerated to find the relatively low likelihood germ line transformation events which have occurred. It has been discovered that using in the transformation process a marker gene linked to the gene of interest, and by excising a segment of the stem of the shoot during the regeneration process and assaying the segment for the marker gene, certain patterns or phenotypes can be identified in the stem segment which are associated with an increased frequency of germ line transformation events. As the plants are regenerated, other indices of gene expression, at the first trifoliate leaf stage and at the third or fourth trifoliate leaf stage, also serve as markers of the likelihood of germ line transformation. By using these markers in the relatively early stages of plant regeneration to assay for likelihood of germ line events, it is possible to concentrate regeneration efforts on plants most likely to yield germ line events, and to discard the others, so as to lower the burden and effort in achieving a desired number of transformation events.
