Abstract

We examined the effect of drought-tolerant Bacillus safensis SS-2.7 and B. thuringiensis SS-29.2 strains on the response of four (133, 274, California Wonder—CalW, and Matica) sweet pepper genotypes to water deficiency conditions. Pepper seeds were sown in pots with (treated) and without (control) bacterial strain inoculation. After four weeks of growth under controlled conditions and regular watering, drought was imposed by completely withholding watering for seven days. Under conditions of normal watering, genotype 274 showed better seedling establishment than genotype 133 and CalW, while the slowest was genotype Matica. Antioxidant enzyme activity under drought conditions was genotype and bacterial treatment-dependent. The best response to bacterial treatment in order to cope with severe drought was found in the CalW genotype, while in genotype 133, we determined even faster plant decay during water deficiency in treated seeds. Inoculated seeds of the Matica genotype did not show different antioxidant enzyme activity under normal and drought conditions. According to the obtained results, we concluded that under drought conditions, the most susceptible was genotype 274, moderate susceptibility was detected in genotype 133, and CalW and Matica were the most tolerant genotypes. Our study demonstrates (1) that drought-tolerant Bacillus strains showed a plant growth-promoting effect on some selected pepper genotypes; (2) that there were genotype-dependent antioxidant enzyme activities under drought conditions in response to treatment with a particular bacterial strain; and (3) that we could expect a genotype-dependent response during biostimulant application, especially under stress conditions.

Highlights

  • Plant growth-promoting bacteria (PGPB) with Bacillus and Pseudomonas as the most dominant representatives are known for their ability to colonize plant roots, causing direct or indirect effects

  • The effects of treatment with five drought-tolerant strains on the establishment of four pepper seedlings was assayed, and the obtained results pointed out two bacterial strains Bacillus safensis SS-2.7 (Bs) and B. thuringiensis SS-29.2 (Bt) as the most promising candidates for Plant-Growth Promoting (PGP)

  • Our results showed that treatment with Bs and/or Bt strains able to grow under drought conditions improves the response of some sweet pepper cultivars to drought by enhancing the activity of antioxidant enzymes that reduce the content of H2 O2 and MDA

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Summary

Introduction

Plant growth-promoting bacteria (PGPB) with Bacillus and Pseudomonas as the most dominant representatives are known for their ability to colonize plant roots, causing direct or indirect effects. Plants attract microorganisms by production of root exudates rich in various nutrients essential for rhizobacteria growth [2]. Plants suffer from numerous biotic and abiotic stressors. Osmotic stress usually occurs as a result of a lack of water due to drought and is the most devastating type of abiotic stresses for plants. The production of reactive oxygen species (ROS) increases [3]. One of the major causes of loss of crop and vegetable productivity worldwide is accumulation of ROS as a result of various environmental stresses

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