• Low soil microbial diversity correlates with increased disease severity in wheat. • Inoculation with Pseudomonas inefficax reduces disease, especially in soils with low microbial diversity. • High microbial diversity may hinder inoculant performance due to microbial competition. • Fluviicola enrichment in the rhizosphere correlates with suppression of Bipolaris sorokiniana.

The conversion of forest to agricultural soils is a widespread activity in tropical systems, and its link to nitrous oxide (N₂O) fluxes and nitrogen cycling gene abundance is relevant to understand environmental drivers that may interact with climate change. A current challenge to estimating N₂O emissions from land use conversion is an incomplete understanding of crop-specific impacts on denitrifier communities and the N₂O fluxes driven by differences in the above- and below-ground inputs with crop type. To address this knowledge gap in tree crops, we evaluated N₂O fluxes and denitrification gene abundance and their relationships with soil and plant residue characteristics in citrus and eucalyptus plantations in the field and in soil incubations. We found that the accumulated N₂O fluxes from soil were lower for the two agricultural field sites than those for their adjacent forest sites in dry and wet seasons. The N₂O fluxes were higher in the wet season, and this seasonal difference persisted even when the soils collected from both seasons were incubated under the same moisture and temperature conditions in the lab for 30 days. Increased N₂O fluxes in the wet season were accompanied by an increase in soil nirK and nosZ gene abundance, the dissolved organic carbon (DOC) concentration, and the total soil carbon (C) and nitrogen (N) content. In turn, the abundance of denitrifiers, as indicated by nirK, nirS, and nosZ gene copy numbers, showed a low but significant positive correlation with soil bulk density. Our results suggest that soil moisture, leaf litter, and crop residues influence the seasonal differences in both N₂O fluxes and abundance of denitrifiers in citrus- and eucalyptus-cultivated soils, likely through effects on soil physicochemical characteristics. These findings highlight the overwhelming role of environmental drivers that can make investigating microbial drivers difficult in the field and open the possibility for a better understanding of N cycling processes in tropical soils based on paired field- and incubation-based experimentation.

In this study, we have identified and characterized three genomes from bacteria isolated from the rhizosphere of Triticum aestivum. Streptomyces virginiae CMAA1738 and Paenibacillus ottowii CMAA1739 were obtained from the wheat landrace Iran 1-29-11334, and Pseudomonas inefficax CMAA1741 was isolated from the wheat landrace Karakilcik.

Crop yield decrease is the main concern when a pathogen or plague is identified in an agriculture field. Thus, part of this issue can be attributed to plant-parasitic nematodes (PPNs), such as Meloidogyne species, due to, most of the time, the hard diagnosis, and non-specific symptoms. Its management is mainly based on chemical pesticides, followed by a few potential biological control agents, and the management system. Therefore, this study aimed to evaluate the effects of biological agents in Meloidogyne incognita control in different soil systems. For that, two biological products were chosen, Trichoderma asperellum BV10 and Bacillus amyloliquefaciens BV03, and soils were sampled from three different managements systems: (i) soybean no-tilled system at Goiás state, Brazil; (ii) forest soil at Goiás state, Brazil, and (iii) soybean conventional managed system at Mato Grosso do Sul state, Brazil. Biocontrol and growth promotion effects, volatile organic compounds (VOCs) and soil respiration were determined in vegetation house and laboratory, respectively. As a result, both BV10 and BV03 had significant nematode control activity, comparing to control treatment, in all the three soils systems. Plus, the number of immobile nematodes by potential VOCs had significant increase when BV03 was applied, while the application of BV10 agent raised the soil respiration rate. In conclusion, both biocontrol agents presented great efficiency in control M. incognita, with better performance of BV03. Lastly, more studies must be done to elucidate how the resident soil microbiome can influence on biocontrol agent establishment and performance, as well as the consequence of the application of biological products on soil microbiome network.