Variability in Agronomic and Chemical Characteristics of Spearmint (Mentha spicata L.) Genotypes in Ethiopia

Evaluation activity was conducted using three spearmint genotypes (WG-SPM-Engl, SPM-Fran and SPM-EAS) and one standard check (WGSM-03) at Wondo Genet, Awassa, Debre Zeit and Allagae during 2012 and 2013 for two years. The treatments were arranged in randomized complete block design with four replications. Data on leaf to stem ratio, leaf yield/ha, Essential oil content and essential oil yield were collected and statistically tested. The combined analysis of variance over the testing locations and years indicated the existence of significant variation among spearmint genotypes for all the characters considered in this study. The respective leaf to stem ratio, leaf yield/ha, essential oil content and essential oil yield of the tested genotypes ranged from 1.29 to 2.2, 10.82 to 13.45 t, 0.16 to 0.5% and 18.13 to 67.99 kg, respectively. The highest leaf to stem ratio (2.2) was demonstrated by WG-SPM-Engl and the lowest (1.29) by WG-SPM-Fran. The highest leaf yield/ha was demonstrated by WG-SPM-Fran followed by WG-SPM-Engl; while the lowest value for these agronomic characters were produced by WG-SM03. Compared with WGSM 03, WG-SPM-Fran demonstrated a respective percent increase value of 47.05 and 81.45% on essential oil content and essential oil yield. The overall highest value for essential oil content (0.39%) was recorded at Allagae followed by Wondo Genet (0.35%) and Hawassa (0.34%); while the least value was recorded at Debre Zeit (0.31%). Averaged over the testing locations, the highest essential oil yield/ha (48.29 kg) was recorded at Hawassa and the lowest at Wondo Genet (34.85 kg). Compared with second testing year, a respective percent increase value of 12.12 and 23.18% on essential oil content and essential oil yield was demonstrated in first testing year.