MORPHOLOGICAL AND ESSENTIAL OIL CONTENT DIVERSITY OF IRANIAN MINTS (MENTHA SPP)

There is little information available on morphological and agronomic traits, as well as chemical compositions of Iranian mint landraces. This study was conducted to investigate the morphological, agronomic and oil content characteristics of Iranian mint landraces using twelve landraces, three of which belong to Mentha longifolia, and the remaining, Mentha spicata L, originated from central regions of Iran. Days to 50% and 100% flowering, plant height, number of lateral branches, leaf length, leaf width, herbage yield per plant, number of nodes per main stem, number of nodes per lateral branch, spike length of main stem, number of spikes per plant, height of lateral branches and spike length of lateral branches were recorded and used in this study. The results showed the significant differences among landraces for all tested traits with the exception of the number of nodes per lateral branch. Two accessions, including Mzin3 with 1.9 ml/100g essential oil content, and Mzin6 with 2.1 ml/100g essential oil content, produced the highest essential oil content. Mzin3, with15.9 g/plant herbage dry yield and Mzin6 8.1 g/plant, produced the highest and lowest herbage yield. Genotypic and phenotypic coefficients of variation were high for the spike length of the main stem (32.3%, 29.7 %), the number of spikes per plant (41.7%, 28.5%), and the essential oil content (38.5%, 34.1%), and was low for days to 50% flowering (11.9%, 10.7 %), days to 100% flowering (9.2%, 6.5%) and number of nodes per main stem (9.7%, 6.9%). Stepwise regression analysis indicated that leaf length justified 53 percent of the total variation and was accounted as the most important component of essential oil content. Cluster analysis divided the landraces into 3 groups, each of which having 5, 3 and 4 clones. The number of nodes per main stem, number of lateral branches, spike width of main stem, leaf width, days to 50% flowering, plant height and nodes per lateral branches were the major sources of diversity among the mint clones. Strong association was observed between leaf length and essential oil content (r = 0.73). Therefore, under tested environmental conditions, leaf length may be used as a morphological criterion for selecting clones with high essential oil content in mint.