In Vitro Storage Conditions for Mint Germplasm

Abstract

Four tissue-cultured mints, Mentha arvensis L., M. spicata L., M. suaveolens Ehrh. hybrid, and M. suaveolens cv. Variegata, were evaluated for survival during storage in media containing three concentrations of N and in four light and temperature regimes. Shoots were placed in plastic, five-chamber, tissue-culture bags on Murashige and Skoog medium (1962) containing 25%, 50%, and 100% of the normal N concentration (MS-N) and stored at 4 °C and –1 °C in darkness, at 4 °C with a 12-hour photoperiod, and at 25 °C with a 16-hour photoperiod. Shoots of all four genotypes stored at 25 °C were in excellent condition after 6 months but required subculture after 18 months. Condition ratings of stored shoots varied with genotype and N concentration. Cultures survived longest at 4 °C with a 12-hour photoperiod on 50% MS-N. Under this regime, all four genotypes were rated in good condition at 30 months but declined to poor condition by 36 months. Based on these data, I recommend that mint cultures be stored on MS medium with 50% MS-N at 4 °C with a 12-hour photoperiod. This regime should provide a minimum of 24 to 36 months of storage before subculture is required. Cold-sensitive genotypes could be stored for 18 months at 25 °C on 50% MS-N medium.