The influence of plant growth-promoting rhizobacteria and arbuscular mycorrhizal fungi dual inoculation on tomato plants against abiotic stress regime
Date
2024
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Publisher
University of Delaware
Abstract
Abiotic stress, such as stress from lack of nutrients or water, is responsible for over half of all global crop loss each year. When plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) are added to the soil or plant roots, they act as “biological fertilizers” to mitigate abiotic stress and promote plant growth. Conventionally, PGPRs and AMFs are used independently to enhance plant growth. It is speculated that dual inoculation may reduce drought and limited nutrient stress by reducing oxidative stress, increasing photosynthetic activity, water and nutrient uptake, and plant growth. However, studies showing the plant growth effects of dual PGPR and AMF inoculations are lacking. We investigated whether AMF Rhizophagus irregularis and PGPR Bacillus subtilis ‘UD1022’ would improve the growth of tomato plants grown under limited nutrient (phosphorus) and drought stress conditions. We found that singular and dual inoculations with UD1022 and R. irregularis did not improve plant growth under standard (control) conditions, phosphorus limitation, or drought stress. Singular and dual inoculation treatments with UD1022 induced plant stress under all conditions (control, limited phosphorus, drought stress). PGPR overabundance on bacteria likely competed with plants for resources, limiting plant growth. In the drought stress study, singular and dual UD1022 inoculation treatments decreased stomatal width for plants grown under normal conditions, but not for plants exposed to drought stress. UD1022 and R. irregularis independently and dually colonized plant roots under control, low phosphorus, and drought stress conditions. Successful dual colonization indicates a lack of antagonism between UD1022 and R. irregularis. Further research is needed regarding species-specific interactions between plants, PGPRs, and AMFs, to understand how to better mitigate abiotic stress with biological fertilizer applications.
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Keywords
Abiotic stress, Arbuscular mycorrhizal fungi, Biotic stress, Dual inoculation, Plant growth-promoting rhizobacteria