Volatile Organic Compounds from Rhizobacteria Increase the Biosynthesis of Secondary Metabolites and Improve the Antioxidant Status in Mentha piperita L. Grown under Salt Stress

Abstract

Salinity is a major abiotic stress factor that affects crops and has an adverse effect on plant growth. In recent years, there has been increasing evidence that microbial volatile organic compounds (mVOC) play a significant role in microorganism–plant interactions. In the present study, we evaluated the impact of microbial volatile organic compounds (mVOC) emitted by Bacillus amyloliquefaciens GB03 on the biosynthesis of secondary metabolites and the antioxidant status in Mentha piperita L. grown under 0, 75 and 100 mM NaCl. Seedlings were exposed to mVOCs, avoiding physical contact with the bacteria, and an increase in NaCl levels produced a reduction in essential oil (EO) yield. Nevertheless, these undesirable effects were mitigated in seedlings treated with mVOCs, resulting in an approximately a six-fold increase with respect to plants not exposed to mVOCs, regardless of the severity of the salt stress. The main components of the EOs, menthone, menthol, and pulegone, showed the same tendency. Total phenolic compound (TPC) levels increased in salt-stressed plants but were higher in those exposed to mVOCs than in stressed plants without mVOC exposure. To evaluate the effect of mVOCs on the antioxidant status from salt-stressed plants, the membrane lipid peroxidation was analyzed. Peppermint seedlings cultivated under salt stress and treated with mVOC showed a reduction in malondialdehyde (MDA) levels, which is considered to be an indicator of lipid peroxidation and membrane damage, and had an increased antioxidant capacity in terms of DPPH (2,2-diphenyl−1-picrylhydrazyl) radical scavenging activity in relation to plants cultivated under salt stress but not treated with mVOCs. These results are important as they demonstrate the potential of mVOCs to diminish the adverse effects of salt stress.

Elucidating the interaction of rhizosphere bacteria and environmental factors in influencing active ingredient content of Lycium barbarum fruit in China

“…CaB5 can induce elevated levels of diosgenin biosynthesis in Trigonella foenum‐graecum (Jasim et al, 2015). B. amyloliquefaciens can increase the level of total phenolic compounds and the antioxidant capacity of Mentha piperita under salt stress (Cappellari et al, 2020). Therefore, these dominant genera may play an important role in the growth stage of L. barbarum and contribute to the accumulation of active ingredients in the fruit.…”

Do Volatiles Affect Bacteria and Plants in the Same Way? Growth and Biochemical Response of Non-Stressed and Cd-Stressed Arabidopsis thaliana and Rhizobium E20-8

“…This effect was linked to the change in the bacterial volatilome induced by salinity, which changed the expression of plant genes coding antioxidant enzymes, and thus reduced lipid peroxidation and phenol oxidation [ 75 , 76 ]. Cappellari et al (2020) [ 49 ] exposed Mentha piperita to NaCl and observed that bacterial volatiles decreased membrane damage.…”

“…In a study by Zhou et al (2017) [ 24 ], the release of volatiles by Bacillus amyloliquefaciens (strain SAY09) conferred increased Cd tolerance in A. thaliana plants. Another Bacillus amyloliquefaciens strain (GB03) also showed the ability to release volatiles able to increase plant growth and chlorophyll content and to change the morphological characteristics of Mentha piperita plants, increasing their salt tolerance [ 49 ]. Under stressful conditions (such as exposure to Cd), are the effects of bacterial volatiles on plants and bacteria shifted?…”

An Evaluation of Aluminum Tolerant Pseudomonas aeruginosa A7 for In Vivo Suppression of Fusarium Wilt of Chickpea Caused by Fusarium oxysporum f. sp. ciceris and Growth Promotion of Chickpea

“…Additionally, Trichoderma harzianum and Bacillus subtillis secrete β-1,3 glucanase enzymes that have an inhibitory effect on chickpea wilt by inhibiting the pathogen’s growth [ 23 , 26 ]. Volatile organic compounds (VOCs) produced by PGPBs suppress phytopathogenic growth and produce morphological and physiological changes to plants, such as an increase in chlorophyll content, which further improves plant growth [ 27 ].…”