What question did this study set out to answer?

The research aims to assess how Bacillus amyloliquefaciens affects the growth and survival of mint microplants during ex vitro adaptation.

April 5, 2026Open Access

Bacterization With a Strain of Bacillus Amyloliquefaciens to Increase the Adaptability of Mentha Longifolia and Mentha Spicata Microclones in Ex Vitro Conditions

Key Points

The research aims to assess how Bacillus amyloliquefaciens affects the growth and survival of mint microplants during ex vitro adaptation.
Controlled environment climate chamber was used for testing
Mint species included were Mentha longifolia and Mentha spicata
Growth metrics such as shoot length, biomass, and chlorophyll content were measured
Comparison was made between treated and untreated control plants
In M. longifolia, shoot length increased by 57.5% and dry biomass by 128.4%
Chlorophyll a and b showed increases of 21.7% and 9.1%, respectively
M. spicata exhibited a 195.3% increase in wet biomass but a decrease in chlorophyll a by 7.2%
Overall increase in NDVI indicates better photosynthetic activity, particularly in M. longifolia

Abstract

The aim of the study is to evaluate the efficacy of Bacillus amyloliquefaciens strain in increasing the survival rate of mint microplants (Mentha longifolia and Mentha spicata) during ex vitro adaptation in a controlled environment climate chamber. The results revealed a statistically significant and species-specific effect of the biopreparation. In M. longifolia, treatment caused complex growth stimulation: shoot length increased by 57.5 %; leaf area – by 209; raw biomass – by 166.2; dry biomass – by 128.4 %. The physiological status of plants improved significantly: the content of chlorophyll a increased by 21.7 %; chlorophyll b – by 9.1, and the total carotenoid content – by 12.5 % compared to the control of untreated plants. Overall, a 9–22 % increase in chlorophyll and carotenoid content and a 39 % increase in the NDVI (to 0.57) were observed, indicating activation of the photosynthetic apparatus. In M. spicata, the response was selective: despite a similarly significant increase in wet (195.3 %) and dry (163.2 %) biomass and an increase in NDVI (22.7 %), a decrease in the concentration of key photosynthetic pigments was recorded: chlorophyll a content decreased by 7.2 %, and the sum of chlorophylls (a + b) by 6.9 % compared to the control. This indicated a different adaptation strategy, in which resources are redistributed toward enhanced vegetative growth rather than pigment synthesis. High potential for targeted use of the B. amyloliquefaciens S21 strain as a microbiological biofortification for managing valuable plant traits was identified. For M. longifolia, this strain is recommended as an effective biostimulant of photosynthetic productivity and overall growth; for M. spicata, it is used as an agronomic technique for intensifying vegetative mass accumulation. The necessity and feasibility of developing specialized, species-specific protocols for the use of microbial inoculants in modern breeding programs aimed at producing high-quality and adaptable planting material with desired economic characteristics are substantiated.

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