Abstract
<jats:p>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.</jats:p>