Traces of cadmium (Cd) have been reported in some chocolate products due to soils with Cd and the high ability of cacao plants to extract, transport, and accumulate it in their tissues. An agronomic strategy to minimize the uptake of Cd by plants is the use of cadmium-resistant bacteria (Cd-RB). However, knowledge about Cd-RB associated with cacao soils is scarce. This study was aimed to isolate and characterize Cd-RB associated with cacao-cultivated soils in Colombia that may be used in the bioremediation of Cd-polluted soils. Diversity of culturable Cd-RB, qualitative functional analysis related to nitrogen, phosphorous, carbon, and Cd were performed. Thirty different Cd-RB morphotypes were isolated from soils with medium (NC, Y1, Y2) and high (Y3) Cd concentrations using culture media with 6 mg Kg-1 Cd. Cd-RB were identified based on morphological and molecular analyses. The most abundant morphotypes (90%) were gram-negative belong to Phylum Proteobacteria and almost half of them showed the capacity to fix nitrogen, solubilize phosphates and degrade cellulose. Unique morphotypes were isolated from Y3 soils where Burkholderia and Pseudomonas were the dominant genera indicating their capacity to resist high Cd concentrations. P. putida GB78, P. aeruginosa NB2, and Burkholderia sp. NB10 were the only morphotypes that grew on 18 up to 90 (GB78) and 140 mg Kg-1 Cd (NB2-NB10); however, GB78 showed the highest Cd bioaccumulation (5.92 mg g-1). This study provides novel information about culturable Cd-RB soil diversity with the potential to develop biotechnology-based strategies.

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Traces of cadmium (Cd) have been reported in chocolate products due to growing cacao plants in soils with Cd and the ability of cacao plants to accumulate it. A strategy to minimize this uptake of Cd is by using cadmium-tolerant bacteria (CdtB) to sequester the Cd. This study was aimed to isolate and characterize CdtB associated with cacao-cultivated soils in Cundinamarca-Colombia. Thirty CdtB morphotypes were isolated and almost half of them showed the capacity to fix nitrogen, solubilize phosphates and degrade cellulose. Besides, all strains were selected for analysis of 16S rRNA sequence. The soil with the highest natural concentration of Cd (location Y3) showed higher abundance, unique morphotypes, and dominance of isolated CdtB. Pseudomona putida GB78, Pseundomona aeruginosa NB2, and Burkholderia sp. NB10 were the only morphotypes that grew on 18 up to 90 (GB78) and 140 mg Kg− 1 Cd (NB2-NB10). GB78 showed the highest Cd bioaccumulation (5.92 mg g− 1). Our results expand the knowledge about culturable CdtB in cacao-cultivated soils with the potential to develop soil management strategies to mitigate the uptake of Cd by cacao plants, thereby preventing the potential impact on human health, food safety, and the cacao economy.

Strawberry (Fragaria ×ananassa Duch.) is a commercially important crop with high water requirements, for which it is necessary to find strategies that mitigate the influence of water deficit on plant growth. This study was aimed to evaluate the effects of shading on the vegetative growth of strawberry cv. Sweet Ann under water deficit. The treatments consisted of the combination of two levels of shading (light intensity reduced on 47% vs. non-shaded plants) and two levels of water availability (water deficit vs. well-watered plants). The water deficit reduced the leaf water potential from −1.52 to −2.21 MPa, and diminished stomatal conductance, net photosynthetic rate (from 9.13 to 2.5 μmol m−2 s−1), photosystem II photochemical efficiency (from 0.79 to 0.67), and biomass accumulation, while increased the electrolyte leakage. The shading allowed the water-deficient plants to maintain water potential (−1.58 MPa) and photosystem II efficiency (0.79) and to increase water use efficiency (from 14.80 to 86.90 μmol CO2/mmol H2O), net photosynthetic rate (from 2.40 to 9.40 μmol m−2 s−1) and biomass of leaves, crowns, and roots compared to non-shaded plants without water limitation. These results suggest that a reduction in incident light intensity attenuates the effects of stomatic and non-stomatic limitations caused by water deficit during vegetative growth of strawberry.