Characterization of bacterial endophytes from the roots of native and cultivated Brazil nut trees (Bertholletia excelsa)

Abstract

Brazil nut is a very important nontimber forest product in the Amazon region. Propagation of this tree still represents a challenge due to slow and uneven seed germination. In this context, plant growth-promoting bacteria can facilitate the process of propagation. The aims of this study were to isolate and characterize endophytic bacteria from the roots of Brazil nut trees in native terra firme forest and cultivation areas in northern Brazil, and to identify mechanisms by which bacteria act in plant growth promotion. Overall, 90 bacterial isolates were obtained from the roots of Brazil nut trees in monoculture, agroforestry and native forest areas by using different semisolid media. The isolates were characterized by sequencing the 16S rRNA gene. Plant growth-promoting characteristics were evaluated by the presence of the nifH gene, aluminum phosphate solubilization and the production of indole compounds. The isolates were affiliated with 18 genera belonging to 5 different classes (α-Proteobacteria, β-Proteobacteria, γ-Proteobacteria, Bacilli and Actinobacteria). The genus Bacillus was predominant in the forest and monoculture areas. Fourteen isolates presented the nifH gene. Most of the bacteria were able to solubilize aluminum phosphate and synthetize indole compounds. The results indicated high diversity of endophytic bacteria present among the roots of Brazil nut trees, mainly in the agroforestry area, which could be related to soil attributes. Among the 90 isolates, the 22 that presented the best results regarding plant growth promotion traits were good candidates for testing in seedling production of Brazil nut trees.

Characterization of Pseudomonas bacteria of Piper tuberculatum regarding the production of potentially bio-stimulating compounds for plant growth

“…Despite advances in the identification of endophytic bacteria in a number of plant species worldwide (Hallmann et al 1997;Gaiero et al 2013;Santoyo et al 2016), few studies have reported such microorganisms in plants from the Amazon region (Coelho et al 2011;Nascimento et al 2015;Chalita et al 2019). As examples of bacteria with the potential to contribute to sustainable agriculture, Pt12 and Pt13, identified as Pseudomonas putida and Pseudomonas sp., respectively, were isolated from roots of Piper tuberculatum Jacq.…”

Agroforestry potential for adaptation to climate change: A soil‐based perspective

“…PGPR has been also used as a bio‐fertilizer to aid plants in coping with biotic and abiotic stresses (also denoted as symbiogenics), thereby promoting crop productivity (Khalid et al, 2017). Chalita et al (2019) reported a high diversity of root endophytes in AFS as compared with forest or monocultures which could be related to soil properties that promoted plant growth. These organisms confer stress resistance through diverse mechanisms of plant‐microbe‐soil associations that combat problems of warming and aridification (Coleman‐Derr & Tringe, 2014; Singh & Gupta, 2018).…”

Understanding the Technical-Scientific Gaps of Underutilized Tropical Species: The Case of Bactris gasipaes Kunth

“…Chalita et al [ 40 ] identified Pseudomonas putida , Burkholderia ambifaria, and Burkholderia sp. in agroforestry systems containing peach palms.…”

“…The use of insecticides or other biocides can be an alternative but may not assure the control of contamination and contribute to increasing microorganism resistance [ 70 ]. Good nutrition and association with symbiotic microorganisms could reinforce the peach palm’s resistance to these diseases and pests [ 37 , 38 , 40 , 70 ], however, more studies on the peach palm that focus on biological control are still needed.…”