COMPARISON OF SELECTIVE AGENTS FOR USE WITH THE SELECTABLE MARKER GENE BAR IN MAIZE TRANSFORMATION

The effectiveness of four phosphinothricin (PPT)-based selective agent s were evaluated for use in maize transformation: glufosinate, bialaph os, Basta(R) and Herbiace(R). Glufosinate and its commercial formulati on, Basta(R), were less effective in controlling growth of non-transge nic corn callus than the tripeptide, bialaphos, or its commercial form ulation, Herbiace(R). Addition of 25 mM L-proline had no significant e ffect on selection when using bialaphos. However, when L-proline was i ncluded with the selective agent glufosinate, selection was inhibited and callus growth was enhanced. At four weeks, callus growth on 0.3, 1 .0 and 3.0 mg l-1 glufosinate in the presence of proline was 76, 43, a nd 21% of control growth, respectively, and in the absence of proline was only 32, 9, and 6% of control growth. Optimized selection protocol s for Basta(R) and bialaphos yielded comparable numbers of transforman ts. Using these protocols, fertile transgenic plants were regenerated from transformed callus cultures.