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. 2022 Sep 9;23(18):10449.
doi: 10.3390/ijms231810449.

Effects of Rhizosphere Bacteria on Strawberry Plants (Fragaria × ananassa Duch.) under Water Deficit

Dominika Paliwoda  1 , Grzegorz Mikiciuk  1 , Małgorzata Mikiciuk  2 , Anna Kisiel  3   4 , Lidia Sas-Paszt  5 , Tymoteusz Miller  3   4
Affiliations

Effects of Rhizosphere Bacteria on Strawberry Plants (Fragaria × ananassa Duch.) under Water Deficit

Dominika Paliwoda et al. Int J Mol Sci. .

Abstract

Due to the observed climate warming, water deficiency in soil is currently one of the most important stressors limiting the size and quality of plant crops. Drought stress causes a number of morphological, physiological, and biochemical changes in plants, limiting their growth, development, and yield. Innovative methods of inducing resistance and protecting plants against stressors include the inoculation of crops with beneficial microorganisms isolated from the rhizosphere of the plant species to which they are to be applied. The aim of the present study was to evaluate 12 different strains of rhizosphere bacteria of the genera Pantoea, Bacillus, Azotobacter, and Pseudomonas by using them to inoculate strawberry plants and assessing their impact on mitigating the negative effects of drought stress. Bacterial populations were assessed by estimates of their size based on bacterial counts in the growth substrate and with bioassays for plant growth-promoting traits. The physiological condition of strawberry plants was determined based on the parameters of chlorophyll fluorescence. The usefulness of the test methods used to assess the influence of plant inoculation with rhizosphere bacteria on the response of plants growing under water deficit was also evaluated. A two-factor experiment was performed in a complete randomization design. The first experimental factor was the inoculation of plant roots with rhizosphere bacteria. The second experimental factor was the different moisture content of the growth substrate. The water potential was maintained at -10 to -15 kPa under control conditions, and at -40 to -45 kPa under the conditions of water deficit in the substrate. The tests on strawberry plants showed that the highest sensitivity to water deficiency, and thus the greatest usefulness for characterizing water stress, was demonstrated by the following indices of chlorophyll "a" fluorescence: FM, FV, FV/FM, PI, and Area. Based on the assessment of the condition of the photosynthetic apparatus and the analysis of chlorophyll "a" fluorescence indices, including hierarchical cluster analysis, the following strains of rhizosphere bacteria were found to have favorable effects on strawberry plants under water deficit: the Bacillus sp. strains DLGB2 and DKB26 and the Pantoea sp. strains DKB63, DKB70, DKB68, DKB64, and DKB65. In the tests, these strains of Bacillus sp. exhibited a common trait-the ability to produce siderophores, while those of Pantoea sp. were notable for phosphate mobilization and ACCD activity.

Keywords: PGPR; bacterial counts; drought stress; fluorescence of chlorophyll “a”; strawberry.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Bacterial counts in growth substrate after inoculation with rhizosphere bacteria under different levels of substrate moisture.
Figure 2
Figure 2
Frequency of statistically significant changes in the indices of chlorophyll “a” fluorescence in strawberry as a result of inoculation with rhizosphere bacteria, between optimal soil moisture and water deficit conditions.
Figure 3
Figure 3
Cluster analysis showing the similarities of the variability of chlorophyll “a” fluorescence indices, depending on the different substrate moisture levels and inoculation with rhizosphere bacteria, where: OM—optimal moisture, WD—water deficit.
Figure 4
Figure 4
F0 in the leaves of strawberry plants inoculated with rhizosphere bacteria growing under different substrate moisture levels, where: OM—optimal moisture, WD—water deficit.
Figure 5
Figure 5
FM in the leaves of strawberry plants inoculated with rhizosphere bacteria growing under different substrate moisture levels, where: OM—optimal moisture, WD—water deficit.
Figure 6
Figure 6
FV in the leaves of strawberry plants inoculated with rhizosphere bacteria growing under different substrate moisture levels, where: OM—optimal moisture, WD—water deficit.
Figure 7
Figure 7
FV/FM in the leaves of strawberry plants inoculated with rhizosphere bacteria growing under different substrate moisture levels, where: OM—optimal moisture, WD—water deficit.
Figure 8
Figure 8
TFM in the leaves of strawberry plants inoculated with rhizosphere bacteria growing under different substrate moisture levels, where: where: OM—optimal moisture, WD—water deficit.
Figure 9
Figure 9
PI in the leaves of strawberry plants inoculated with rhizosphere bacteria growing under different substrate moisture levels, where: OM—optimal moisture, WD—water deficit.
Figure 10
Figure 10
‘Area’ parameter in the leaves of strawberry plants inoculated with rhizosphere bacteria growing under different substrate moisture levels, where: OM—optimal moisture, WD—water deficit.
Figure 11
Figure 11
The plantlet of the strawberry cv. Polka.
Figure 12
Figure 12
Strawberry cv. Polka at the time of inoculation.
See this image and copyright information in PMC

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