Soil management in a mountain agroecosystem and clubroot disease

Abstract

Clubroot, caused by Plasmodiophora brassicae, is a disease limiting the production of Brassica species. Its severity varies according to the density of the pathogen's resting spores and environmental conditions. Although the soil environment (including its physical, chemical and biological characteristics) is determinant in the development of the disease, little is known regarding these characteristics in tropical regions, such as Brazil. The objective of this study was to investigate the relationships between soil attributes, bacterial population composition and clubroot intensity in a tropical mountain agroecosystem. Soil and plant samples were collected from 17 cauliflower‐producing localities in Nova Friburgo, Brazil. The physical and chemical attributes, the bacterial population composition, the number of pathogen resting spores in the soil samples, and the clubroot severity were evaluated. Based on bacterial population composition, two distinct groups of soils were identified, which varied in attributes such as organic matter, potential acidity, pH and disease severity. The organic matter level was associated with differences in soil acidity, bacterial population composition and disease intensity, but there was not a cause and effect relationship between bacterial population composition and clubroot severity. Under the conditions of this agroecosystem, soils with increased organic matter presented higher acidity potential (H + Al), which was strongly correlated to clubroot severity. Thus, high acidity potential could be a key factor leading to clubroot development in mountain regions of Brazil.

Bacterial composition in brassica‐cultivated soils with low and high severity of clubroot

“…Bhering et al. (2020) verified that variations in potential acidity (H + Al) affected the composition of bacterial populations in soils and that high levels H + Al are strongly correlated with clubroot severity. Under these conditions, a reduction in root development takes place due to a decrease in pH and increments in toxic exchangeable aluminium levels and may consequently affect the availability of nutrients such as Ca and Mg.…”

“…Also, P. brassicae is exposed to unfavourable environmental conditions, of biotic or abiotic nature, only for a short period of time, when the primary zoospores swim naked and free up to the root hairs where they penetrate and start the infection process (Dixon, 2014). Management techniques that promote soil enrichment and the improvement of its chemical, physical and biological properties can contribute to inhibit the germination of resting spores and the process of root hair infection by primary zoospores (Bhering et al., 2020; Dixon, 2014).…”

Biofumigation with species of the Brassicaceae family: a review

“…The present survey included tests that used brassica species to control fungi (Tables 1 and 2), oomycetes (Table 3), nematodes (Table 4), phytopathogenic bacteria, and protozoa (Table 5); weeds; and insects, including some species that are stored product pests (Table 6). Notably, in this analysis, the pathogen Plasmodiophora brassicae was grouped as a protozoan, considering different publications and recent phylogenetic analyses that included this species in the protist supergroup Rhizaria (BURKI et al, 2010;SCHWELM et al, 2015;BHERING et al, 2020).…”

Recomendações de Manejo Visando o Controle da Hérnia das Crucíferas

“…Estas condições favorecem a germinação dos esporos resistentes do patógeno e reduzem a resistência das plantas e, consequentemente, potencializam os processos de infecção das plantas e o aumento da severidade da doença. Concomitantemente, estas condições prejudicam o desenvolvimento das raízes, o que agrava as perdas causadas pela doença (BHERING et al, 2017;BHERING et al, 2020). Pode-se destacar como fatores que contribuem para maior acidez do solo: não realização de calagem (aplicação de calcário), requerida a partir do resultado da análise química e obedecendo à recomendação técnica para a cultura, calagem feita incorretamente e adubação nitrogenada utilizando-se fontes amoniacais como a ureia e o sulfato de amônio (RUARO et al, 2009;BHERING, 2017;SANTOS, 2017;SANTOS, 2020).…”