Oryzalin induces polyploids with superior morphology and increased levels of essential oil production in Mentha spicata L

Efficacy of oryzalin to generate novel genotypes of Mentha spicata L. with superior morphology and enhanced levels of essential oil via in vitro polyploidization was assessed. Micropropagated nodal segments were treated with oryzalin at 20, 40, and 60 mu M for 24 and 48 h. The survival rate of the nodal segments dropped significantly with the increasing concentration and duration of oryzalin. Further, the ploidy level of the survived plants was confirmed using flowcytometry and chromosome counting. A total of six polyploids (2 n = 6x = 72) and six mixoploid plants were obtained. The highest frequency of polyploids (8 %) was induced in treatment where 40 mu M oryzalin was applied for 48 h. The obtained polyploids exhibited significantly larger, thick, dark green leaves with elongated stomata compared with the control genotype. The polyploid plants also displayed higher moisture content and vigorous lateral growth. The essential oil yield of hexaploid M. spicata exhibited a 48.85 % increase, rising from 1.74 % in control to 2.59 % (v/w) in genotype P3. The major components of essential oils were carvone and limonene, which also increased significantly compared with the control genotype. The nutrient profile of the studied genotypes was influenced vastly and showed significant variations. Overall, the employed methodology using oryzalin as an antimitotic agent for polyploid induction in M. spicata was found to be effective. Despite relatively low polyploid induction frequency, the obtained polyploid genotypes demonstrated various superior agronomical traits. The genotypes obtained could serve to aid the commercial demands.

Automated summary

The efficacy of oryzalin in vitro polyploidization of Mentha spicata L. was assessed to generate novel genotypes with superior morphology and enhanced essential oil levels. Nodal segments were treated with different concentrations and durations of oryzalin, resulting in a drop in survival rate. Polyploids and mixoploid plants were obtained, with the highest frequency of polyploids induced at 40 μM oryzalin for 48 hours. These polyploids displayed larger leaves, thicker stomata, higher moisture content, and vigorous lateral growth compared to the control genotype. The essential oil yield of hexaploid M. spicata also significantly increased, along with the major components carvone and limonene. The employed technique using oryzalin as an antimitotic agent proved effective in inducing polyploidy in M. spicata, with the obtained genotypes showing superior agronomical traits that could meet commercial demands.