RESUMO
Arbuscular mycorrhizal fungi (AMF) are mutualistic symbionts considered a key group in soil systems involved in the provision of several ecosystem services. Recently they have been listed by EFSA as organisms to be included in the test battery for the risk assessment of plant protection product (PPPs). This study aimed to contribute to improve the ISO Protocol (ISO 10832: 2009) by assessing the feasibility of using other AMF species under different test conditions. Overall, results showed that AMF species Gigaspora albida and Rhizophagus clarus (selected out of five AMF species) are suitable to be used in spore germination tests using the ISO protocol (14 days incubation with sand or artificial soil as substrate) to test PPPs. However, several modifications to the protocol were made in order to accommodate the use of the tested isolates, namely the incubation temperature (28 °C instead of 24 °C) and the change of reference substance (boric acid instead of cadmium nitrate). The need for these changes, plus the results obtained with the three fungicides tested (chlorothalonil, mancozeb and metalaxyl-M) and comparisons made with literature on the relevance of the origin of AMF isolates in dictating the adequate test conditions, emphasize the importance of adjusting test conditions (AMF species/isolates and test temperature) when assessing effects for prospective risk assessment targeting different climatic zones. So, further studies should be conducted with different AMF species and isolates from different climatic regions, in order to better define which species/isolate and test conditions should be used to assess effects of a particular PPP targeting a given climatic zone.
Assuntos
Fungicidas Industriais/toxicidade , Glomeromycota/efeitos dos fármacos , Micorrizas/efeitos dos fármacos , Microbiologia do Solo , Testes de Toxicidade/métodos , Alanina/análogos & derivados , Alanina/toxicidade , Maneb/toxicidade , Nitrilas/toxicidade , Medição de Risco , Solo/química , Temperatura , Fatores de Tempo , Zineb/toxicidadeRESUMO
Plant root exudates contain a range of low molecular weight metabolites that trigger many of the structural and physiological changes associated with the progression and establishment of mycorrhizal symbiosis. Here, the physiological response triggered by acetosyringone (AS) was studied in Glomus intraradices. Incubation of G. intraradices spores with AS resulted in an overall increase in hyphal respiration. A G. intraradices cDNA library was then screened with a total cDNA probe obtained from the AS-treated spores and mycelium. cDNAs from genes induced in AS-treated G. intraradices were assigned to different functional categories, such as protein synthesis, membrane transport, signal transduction, and general metabolism, but without further information regarding their function or identity. A cDNA coding a fragment of a histidine kinase was also induced by AS, suggesting a two-component mediated response to the metabolite. In addition, the differential accumulation of a cruciform DNA-binding protein mRNA, termed as GiBP1, was also observed. Time-course experiments demonstrated the rapid accumulation of GiBP1 within 2 h of AS induction. These results indicate the presence of a set of fungal genes that are induced by AS. These findings are discussed in terms of the possible molecular events that follow the exchange of signals between mycorrhizal symbionts.