Plant-plant competition outcomes are modulated by plant effects on the soil bacterial community.

Competition is a key process that determines plant community structure and dynamics, often mediated by nutrients and water availability. However, the role of soil microorganisms on plant competition, and the links between above- and belowground processes, are not well understood. Here we show that the effects of interspecific plant competition on plant performance are mediated by feedbacks between plants and soil bacterial communities. Each plant species selects a singular community of soil microorganisms in its rhizosphere with a specific species composition, abundance and activity. When two plant species interact, the resulting soil bacterial community matches that of the most competitive plant species, suggesting strong competitive interactions between soil bacterial communities as well. We propose a novel mechanism by which changes in belowground bacterial communities promoted by the most competitive plant species influence plant performance and competition outcome. These findings emphasise the strong links between plant and soil communities, paving the way to a better understanding of plant community dynamics and the effects of soil bacterial communities on ecosystem functioning and services.

Ocorrência de cochonilhas em espinheira-santa (Maytenus ilicifolia Mart. ex Reissek) / Occurrence of mealybugs in "espinheira-santa" (Maytenus ilicifolia Mart. ex Reissek)

Maytenus ilicifolia é uma espécie medicinal nativa do Brasil que vem sendo cultivada para atender a crescente demanda do mercado. Os fatores que interferem na produção, tal como a incidência de pragas e doenças, devem ser estudados para garantir o incremento na produtividade. O objetivo deste trabalho foi registrar a ocorrência e a identificação de cochonilhas associadas a 15 acessos de espinheira-santa (Maytenus ilicifolia) do Banco Ativo de Germoplasma da Embrapa Clima Temperado e do Instituto Federal Sul-rio-grandense. Foi registrada a quantidade de plantas infestadas em cada acesso e identificado, em laboratório, as espécies de cochonilhas infestantes. O número de plantas infestadas variou entre os acessos. Foram identificadas as cochonilhas Ceroplastes sp. e Saissetia oleae, família Coccidae. Dos 10 acessos infestados, 23 (11,3%) plantas apresentaram infestação com Ceroplastes sp. e, apenas uma (0,5%), com Saissetia oleae. O acesso 133 mostrou a maior incidência de Ceroplastes sp. (33,3%), seguido do acesso 130 (25,0%). O acesso 123 foi o que apresentou menor quantidade de plantas infestadas (4,8%). Saissetia oleae ocorreu em apenas uma planta, pertencente ao acesso 136 (5,6%).

Maytenus ilicifolia is a medicinal species native to Brazil which has been cultivated to meet the growing market demand. Factors that interfere with the production, such as the incidence of pests and diseases, should be studied to ensure increased productivity. The aim of this study was to record the occurrence and the identification of mealybugs associated with 15 "espinheira-santa" (Maytenus ilicifolia) accessions from the Active Germplasm Bank of "Embrapa Clima Temperado" and "Instituto Federal Sul-rio-grandense". The quantity of infested plants in each accession was recorded and the species of infested mealybugs were identified in the laboratory. The number of infested plants varied among accessions. The identified mealybugs were Ceroplastes sp. and Saissetia oleae, family Coccidae. Of 10 infested accessions, 23 plants (11.3%) showed infestation with Ceroplastes sp., and only one (0.5%) with Saissetia oleae. Accession 133 showed the highest incidence of Ceroplastes sp. (33.3%), followed by accession 130 (25.0%). Accession 123 had the least amount of infested plants (4.8%). Saissetia oleae occurred in only one plant, belonging to accession 136 (5.6%).