Banca de DEFESA: JOSÉ MAURICIO FAJARDO DA CUNHA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : JOSÉ MAURICIO FAJARDO DA CUNHA
DATE: 26/03/2026
TIME: 09:00
LOCAL: Embrapa Agrobiologia - Sala de Reuniões do Pavilhão Johanna Döbereiner
TITLE:

Bioprospecting of Bacillaceae bacteria for the control of the etiological agent of clubroot.

KEY WORDS:

biocontrol; Brassica sp.; Plasmodiophora brassicae

PAGES: 141
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Fitotecnia
SPECIALTY: Fisiologia de Plantas Cultivadas
SUMMARY:

Clubroot, caused by Plasmodiophora brassicae, compromises the productivity of Brassica species and presents limited control options, mainly due to the persistence and dissemination of resting spores in the soil. In this context, members of the family Bacillaceae represent promising biotechnological tools for disease management. Therefore, the objective of this study was to bioprospect bacteria from the family Bacillaceae for the control of the causal agent of clubroot. For this purpose, 54 root samples from cruciferous plants and 37 soil samples were collected from nine producing farms located in the Mountain Region of the state of Rio de Janeiro, Brazil. The samples were processed for the isolation of endospore-forming bacteria, resulting in a proprietary collection of 187 plant-associated isolates and 217 soil isolates. As P. brassicae cannot be cultivated in vitro, the initial screening of strains was conducted through indirect selection based on visual diagnosis, using Fusarium oxysporum f. sp. lycopersici and Magnaporthe oryzae, which share similarities in cell wall composition. The first screening stage prioritized 139 isolates. In vitro validation was performed using antagonism assays with parallel streaks in a completely randomized design. The assays were analyzed using the Kruskal–Wallis test for overall comparison among treatments, followed by Dunn’s test with Benjamini–Hochberg correction at a 5% probability level. Nineteen strains showing mycelial area inhibition indices greater than 70% were selected.

Subsequently, two greenhouse experiments evaluated the effects of the preselected strains on biological responses related to disease severity caused by P. brassicae and on growth promotion in cauliflower plants. Experiment I was conducted in a two-level factorial design (with and without pathogen), including 19 strains, one negative control (water), and five replicates arranged in randomized blocks, and selected five potential biological control agents based on disease severity reduction criteria. Experiment II consisted of six treatments in a two-level factorial design (with and without pathogen), with ten replicates, also arranged in randomized blocks. Greenhouse experiments were analyzed using a generalized linear model (GLM; ANODEV), with mean comparisons performed using Sidak/Fisher tests at a 5% probability level. Sequencing of the 16S rDNA gene of the strains was carried out, followed by sequence processing using BioEdit. Taxonomic identification was performed based on similarity analysis using BlastN and EzBioCloud Pro. Phylogenetic analysis was conducted using the Neighbor-Joining method for comparative clustering with reference strains. All evaluated bacterial isolates belonged to the class Bacilli, with a predominance of the family Bacillaceae. The strains showing the best biocontrol performance belonged to the Bacillus subtilis complex. Biochemical assays for qualitative evaluation of lytic enzymes associated with biological control and plant growth promotion were performed according to institutional standard operating procedures and assessed by visual diagnosis. All evaluated strains showed high production of lytic enzymes, with a minimum of five positive enzymatic activities per isolate. These results demonstrate the potential of the prospected bacteria, highlighting the importance of further analyses to better understand the selected organisms and their mechanisms of action

COMMITTEE MEMBERS:
Presidente - ***.210.947-** - MARCIA SOARES VIDAL - EMBRAPA
Interna - 1213072 - MARGARIDA GORETE FERREIRA DO CARMO
Externo à Instituição - EDERSON DA CONCEIÇÃO JESUS - EMBRAPA
Externo à Instituição - JOSÉ IVO BALDANI - EMBRAPA