Microbial Inoculation Improves Growth, Nutritional and Physiological Aspects of Glycine max (L.) Merr

Abstract

Considering a scenario where there is a low availability and increasing costs of fertilizers in the global agricultural market, as well as a finitude of important natural resources, such as phosphorus (P), this study tested the effect of the inoculation of rhizospheric or endophytic microorganisms isolated from Hymenaea courbaril and Butia purpurascens on the growth promotion of Glycine max (L.) Merr. The tests were conducted in a controlled greenhouse system, and the effects of biofertilization were evaluated using the following parameters: dry biomass, nutritional content, and photochemical and photosynthetic performance of plants. Seed biopriming was performed with four bacterial and four fungal isolates, and the results were compared to those of seeds treated with the commercial product Biomaphos^®. Overall, microbial inoculation had a positive effect on biomass accumulation in G. max, especially in strains PA12 (Paenibacillus alvei), SC5 (Bacillus cereus), and SC15 (Penicillium sheari). The non-inoculated control plants accumulated less nutrients, both in the whole plant and aerial part, and had reduced chlorophyll index and low photosynthetic rate (A) and photochemical efficiency. Strains PA12 (P. alvei), SC5 (B. cereus), and 328EF (Codinaeopsis sp.) stood out in the optimization of nutrient concentration, transpiration rate, and stomatal conductance. Plants inoculated with the bacterial strains PA12 (P. alvei) and SC5 (B. cereus) and with the fungal strains 328EF (Codinaeopsis sp.) and SC15 (P. sheari) showed the closest pattern to that observed in plants treated with Biomaphos^®, with the same trend of direction of the means associated with chlorophyll index, (A), dry mass, and concentration of important nutrients such as N, P, and Mg. We recommend the use of these isolates in field tests to validate these strains for the production of biological inoculants as part of the portfolio of bioinputs available for G. max.

Keywords: bioinputs; endophytic; plant growth promotion; plant mineral nutrition; rhizospheric.

Figure 1

Dry mass of aerial part (A), root dry mass (B) and total dry mass (C) in soybean (Glycine max) plants inoculated with fungal and bacterial strains isolated from Hymenaea courbaril and Butia purpurascens and grown in a controlled greenhouse system. Means followed by the same letter were not significantly different using the Scott–Knott test at 0.05% probability.

Figure 2

Content of the macronutrients N (A), P (B), K, (C), Ca (D), Mg (E), and S (F) and of the micronutrients Fe (G), Mn (H), Cu, (I), Zn (J), and B (K) in the aerial part of soybean (Glycine max) plants inoculated with fungal and bacterial strains isolated from Hymenaea courbaril and Butia purpurascens and grown in a controlled greenhouse system. Means followed by the same letter were not significantly different using the Scott–Knott test at 0.05% probability.

Figure 2

Content of the macronutrients N (A), P (B), K, (C), Ca (D), Mg (E), and S (F) and of the micronutrients Fe (G), Mn (H), Cu, (I), Zn (J), and B (K) in the aerial part of soybean (Glycine max) plants inoculated with fungal and bacterial strains isolated from Hymenaea courbaril and Butia purpurascens and grown in a controlled greenhouse system. Means followed by the same letter were not significantly different using the Scott–Knott test at 0.05% probability.

Figure 3

Content of the macronutrients N (A), P (B), K, (C), Ca (D), Mg (E), and S (F) and of the micronutrients Fe (G), Mn (H), Cu, (I), Zn (J), and B (K) in the roots of soybean (Glycine max) plants inoculated with fungal and bacterial strains isolated from Hymenaea courbaril and Butia purpurascens and grown in a controlled greenhouse system. Means followed by the same letter were not significantly different using the Scott–Knott test at 0.05% probability.

Figure 3

Content of the macronutrients N (A), P (B), K, (C), Ca (D), Mg (E), and S (F) and of the micronutrients Fe (G), Mn (H), Cu, (I), Zn (J), and B (K) in the roots of soybean (Glycine max) plants inoculated with fungal and bacterial strains isolated from Hymenaea courbaril and Butia purpurascens and grown in a controlled greenhouse system. Means followed by the same letter were not significantly different using the Scott–Knott test at 0.05% probability.

Figure 4

Total content of the macronutrients N (A), P (B), K, (C), Ca (D), Mg (E), and S (F) and of the micronutrients Fe (G), Mn (H), Cu, (I), Zn (J), and B (K) in soybean (Glycine max) plants inoculated with fungal and bacterial strains isolated from Hymenaea courbaril and Butia purpurascens and grown in a controlled greenhouse system. Means followed by the same letter were not significantly different using the Scott–Knott test at 0.05% probability.

Figure 4

Total content of the macronutrients N (A), P (B), K, (C), Ca (D), Mg (E), and S (F) and of the micronutrients Fe (G), Mn (H), Cu, (I), Zn (J), and B (K) in soybean (Glycine max) plants inoculated with fungal and bacterial strains isolated from Hymenaea courbaril and Butia purpurascens and grown in a controlled greenhouse system. Means followed by the same letter were not significantly different using the Scott–Knott test at 0.05% probability.

Figure 5

Photosynthetic rate, A (A); transpiration rate, E (B); internal concentration of CO₂, Ci (C); stomatal conductance, Gsw (D); and chlorophyll index (E) in soybean plants (Glycine max) inoculated with fungal and bacterial strains isolated from Hymenaea courbaril and Butia purpurascens and cultivated in a controlled greenhouse system. Means followed by the same letter were not significantly different using the Scott–Knott test at 0.05% probability.

Figure 6

Maximum quantum yield of primary photochemistry (PHI_Po) (A), probability that a trapped exciton moves an electron into the electron transport chain beyond Quinone (Qa) (PSI_O) (B), quantum yield of electron transport (PHI_Eo) (C), photosynthetic performance index (Pi_Abs) (D), absorption flux per RC (ABS. RC) (E), energy flux per RC at t = 0 (TR0. RC) (F), electron transport flux per RC at t = 0 (ET0/RC) (G), and specific dissipated energy flux (DI0. RC) (H) in soybean (Glycine max) plants inoculated with fungal and bacterial strains isolated from Hymenaea courbaril and Butia purpurascens and grown in a controlled greenhouse system. Means followed by the same letter were not significantly different using the Scott–Knott test at 0.05% probability.

Figure 6

Maximum quantum yield of primary photochemistry (PHI_Po) (A), probability that a trapped exciton moves an electron into the electron transport chain beyond Quinone (Qa) (PSI_O) (B), quantum yield of electron transport (PHI_Eo) (C), photosynthetic performance index (Pi_Abs) (D), absorption flux per RC (ABS. RC) (E), energy flux per RC at t = 0 (TR0. RC) (F), electron transport flux per RC at t = 0 (ET0/RC) (G), and specific dissipated energy flux (DI0. RC) (H) in soybean (Glycine max) plants inoculated with fungal and bacterial strains isolated from Hymenaea courbaril and Butia purpurascens and grown in a controlled greenhouse system. Means followed by the same letter were not significantly different using the Scott–Knott test at 0.05% probability.

Figure 7

Correlations between the means of dry biomass, nutrient content, total chlorophyll, gas exchange, and chlorophyll fluorescence a parameters (A) and principal component analysis of these variables (B) in soybean plants (Glycine max) inoculated with fungal and bacterial strains isolated from Hymenaea courbaril and Butia purpurascens and grown in a controlled greenhouse system. SC5 = Bacillus cereus, SC10 = Bacillus thuringiensis, PA12 = Paenibacillus alvei, PA26 = Lysinibacillus fusiformis, SC15 = Penicillium sheari, SC4 = Epicoccum keratinophilum, 33EF = Hamigera insecticola, 328EF = Codinaeopsis sp., Biomaphos^® = Bacillus megaterium and Bacillus subtilis, Control = without microorganisms. * significant at 0.5 and ** significant at 0.1 probability.