In vitro Conservation of Four Mint (Mentha spp.) Accessions

This is a part of long term study of slow growth culture (in vitro storage) of four mints (Mentha spp.) accessions and had been initiated between September 1998 and November 1999. This long term experiment had been assessed in two consecutive phases with four accessions of mint (Mentha spp.), namely MEN 204, MEN 148, MEN 186, and MEN 166 which were diploid, tetraploid and octoploid, respectively. The explants were cultured on MS without hormones for six months. Before culturing the explants in a +2_C cell, they were cultured at 20 and 10_C for one week and three weeks, respectively. In phase I, apical and nodal explants were used. The highest numbers of leaves (12) were obtained from MEN 148 and the lowest (8.62) from MEN 204 for apical explants, but in case of nodal explants MEN 148 was also the highest (15.79) score followed by MEN 186 (15.31). The highest number of branches both for apical and nodal explants were counted in MEN 186. All the accessions showed maximum leaves and branches from nodal explants. Root development was comparatively better in MEN 148 (87%) and MEN 186 (53%) for nodal explants. In phase II, only apical explants were used. The highest number of leaves was counted in MEN 186 (12.43) and the lowest (7.87) in MEN 204. The highest number of branch (1.20) was counted in MEN 148. Root development was similar as of the first phase. The in vitro plantlets were transplanted into the soil of the greenhouse from phase I. After 19 and 32 days of transplanting, MEN 148 and MEN 186 exhibited the maximum plant height both for apical and nodal explants. But MEN 166 and MEN 186 showed the maximum number of branches for both explants after 32 days of transplanting.