Genetic variability, D² analysis and characters association among quantitative and qualitative traits of spearmint (Mentha spicata L.)

An investigation was carried out to assess the genetic variability, genetic divergence and association of pheno-morphic and agronomic traits along with major chemical constituents of essential oil in 41 accessions of spearmint (Mentha spicata L.). Highly significant differences were noted for all 10 economic traits indicating the existence of considerable genetic variability among 41 accessions. High heritability (h2) and high genetic advance was noted for herb yield (120.64%). On the basis of D2 values, all 41 spearmint accessions were grouped into six diverse clusters. The cluster-I was the largest group which consisted of 20 accessions. A significant and positive correlation was observed for plant height with herb yield (0.58 * *; ** = significant at 1% probability level). The herb yield showed the highest direct effect (0.194) for oil yield. According to results, a significant genetic variability was present among 41 accessions, simple selection can be employed to improve essential oil content. More importance should be given to plant height, leaf length, leaf width and herb yield during selection to improve essential oil yield in spearmint.