'EVALUATION OF PEPPERMINT FIELD PERFORMANCE FROM PLANTS REGENERATED FROM MERISTEM TIP CULTURE

'Black Mitchum ' peppermint, commercially meristem tip cultured (M) and then propagated by rooted stem cutting was compared to the same variety (of the original mother stock to M plants) propagated by rooted stem cutting (Non-M). Rooted cuttings of each type were placed into a randomized, complete block experimental design field trial in 1992. In 1993, M plants initially were more vigorous through the first half of the season. Main stems were 15 percent taller and more consistently upright throughout the season. Total above-ground plant dry weight was 17-40 percent greater in M plants compared to Non-M plants. The superior total dry weight advantage for M plants was stem weight. Non-M plants had a greater number of branches and total leaves, greater total leaf weight, and less stem weight than M plants. Though stem thicknesses were similar for both M and Non-M plants, the leaf-to-stem ratio was much greater for Non-M plants than for M plants. This likely explains the earlier and more extensive lodging of Non-M plants through July, in contrast to M plants which remained upright until just prior to harvest in mid-August. For three harvest dates in August, oil yield from plots with Non-M plants was 16-55 percent greater compared to plots with M plants. Oil composition was similar between treatments, except for total heads, which was higher for Non-M than for M plants. These results are discussed with respect to management practices that might improve performance of M plants while taking advantage of the vigor shown following meristem tip culturing