Diversity among Iranian mints in relation to yield and mineral content

Iranian mints (Mentha species) have diverse uses including pharmaceutical, perfumery, food and confectionery. Shoots and leaves of several species of mints are often used as a condiment. There are many landraces of mints in Iran, that elemental content has not yet been determined. The objective of this study was to determine the elemental content range and to evaluate the element contents in two harvests of the Iranian mint landraces. Twelve accessions of mint (Mzin1, Mzin2, Mzin3, Mzin4, Mzin5, Mzin6, Mzin7, Mzin8, Mzin9, Mzin10, Mzin11, and Mzin12) were analyzed for nitrogen (N), phosphorous (P), sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), zinc (Zn), copper (Cu), and manganese (Mn) contents. The herbage yield per plant was also measured at both full flowering and 60 days after the first harvest (regrowth stage). Results indicated a significant difference among mint accessions in the first and second harvests. The analysis of paired t-test between the two harvests showed the significant differences for yield and elemental content except for P and N. The contents of Fe, Zn, Mn, Cu, Mg, Ca, Na, P, and N at the second harvest was higher than the first harvest. The elemental content of Fe, P, and K was widely varied among the different clones at the first and second harvests. Variation in elemental content between the two harvests may have been due to differences in phenological development and genetic differences among clones since the result showed that changes in the elemental content may not be uniform throughout the growing season. In the second harvest, Mzin2 showed the highest Fe content and Mzin6 revealed the highest Mg content. High amounts of Fe and Mg in the herbage tissues indicate that mint could be a good source of Fe and Mg for human nutrition. Cluster analysis showed three groups. Groups 1, 2, and 3 had 5, 2, and 5 clones, respectively. The clustering pattern of the clones revealed that geographic diversity was not related to genetic diversity. Iron, Mg, Ca, P, and N elements were major sources of diversity among mint clones. The Fe and Mg contents were high for Mzin6, Mzin10, Mzin2, Mzin5, and Mzin11, whereas Mzin3, Mzin7, Mzin4, Mzin12, and Mzin8 had high N content. Strategies to improve yield and element content include selection based on genotypic performance, relation between traits, and intercrossing clones.