This is the first report of the occurrence of the F129L mutation in P. pachyrhizi. The practical relevance of this mutation for field efficacy of QoIs needs further investigation. © 2015 Society of Chemical Industry.

A principal doença da goiaba (Psidium guajava L.), após a colheita, é a antracnose, causada por Glomerella cingulata e Colletotrichum gloeosporioides. Estes patógenos e o resíduo de fungicidas em frutos são considerados os principais problemas para a exportaçãodesta fruta. Neste trabalho, foi avaliado o efeito fungitóxico de extratos, decoctos e óleos essenciais de plantas medicinais e aromáticas, no crescimento micelial dos patógenos, in vitro, recomendados como alternativa para o controle químico em pós-colheita. Os extratos aquosos a 10% e os decoctos (subprodutos da hidrodestilação) foram adicionados em BDA, autoclavados e distribuídos em placas de Petri. Os óleos essenciais foram adicionados em três pontos eqüidistantes nas placas de Petri contendo BDA. Discos dos isolados foram repicados para o centro das placas de Petri. O efeito fungitóxico foi avaliado medindo-se o diâmetro das colônias, quando na testemunha ou em qualquer tratamento os patógenos atingiram a borda da placa. O extrato aquoso e o óleo essencial de cravo-da-Índia inibiram em 100% o crescimento de G. cingulata e C. gloeosporioides, sendo este último totalmente inibido pelo óleo essencial de capim-limão. Os decoctos de alecrim, gengibre, calêndula e laranja (Citrus sinensis) apresentaram potencial de inibição sobre os isolados dos patógenos. No controle de C. gloeosporioides, destacaram-se também os decoctos de marcela, camomila e tagetes. A inibição total ou parcial do crescimento micelial de Glomerella cingulata e Colletotrichum gloeosporioides, in vitro, evidenciou a existência de compostos biologicamente ativos, com efeito fungitóxico nos extratos, decoctos e óleos essenciais de plantas medicinais e aromáticas. Isto indica uma aplicação potencial destes produtos no controle alternativo da antracnose em frutos de goiabeira.

No abstract

The ascomycete Monilinia fructicola is the causal agent of brown rot of stone fruit in Brazil, causing major pre- and postharvest losses. For many years, the demethylation inhibitor (DMI) fungicide tebuconazole has been used as the most effective active ingredient for controlling brown rot and, as a result, strains of M. fructicola resistant to this ingredient have emerged in many Brazilian states producing stone fruit. The aim of this study was to investigate the mechanisms associated with the resistance of M. fructicola to DMI tebuconazole. By sequencing the M. fructicola CYP51 (MfCYP51) gene, encoding the azole target sterol 14α-demethylase, a mutation was identified at the nucleotide position 1,492, causing the amino acid substitution from glycine to serine at the codon position 461, associated with reduced tebuconazole sensitivity. In addition, it was observed that MfCYP51 gene expression could play a secondary role in DMI fungicide resistance of M. fructicola strains in Brazil. However, for the specific isolate found to exhibit elevated expression levels of MfCYP51, no insertions that would trigger gene expression were found. Based on the point mutation associated with tebuconazole resistance, an allele-specific polymerase chain reaction method was developed to quickly identify resistant genotypes within the Brazilian population. This is the first report determining molecular mechanisms for DMI resistance identification for M. fructicola isolates from Brazil. This information provides an important advancement for risk assessment of DMI fungicides used to manage brown rot of stone fruit.

The aim of this study was to investigate the sensitivity of Monilinia fructicola isolates to tebuconazole (demethylation inhibitor [DMI]), azoxystrobin (quinone outside inhibitor), and thiophanate-methyl (methyl benzimidazole carbamate) in 118 isolates collected from four states in Brazil from orchards with different histories of fungicide use. Sensitivity to fungicides was determined by inhibition of mycelial growth and spore germination on fungicide-amended media. Polymerase chain reaction was used to determine the frequencies of M. fructicola genotypes exhibiting high (HR) and low (LR) resistance to thiophanate-methyl among sampled populations. Resistance to tebuconazole was found in 15.8% of isolates collected from São Paulo State. The 50% effective concentration (EC50) values varied from 0.01 to greater than 100 μg/ml. The EC50 values for tebuconazole corresponded to its historic use frequency in the orchard; for instance, isolates from orchards with no DMI fungicide use had the lowest mean EC50 value (0.04 μg/ml), while those collected from orchards where more than five DMI fungicide sprays were applied per season had a mean EC50 value of 21.17 μg/ml. All isolates were sensitive to azoxystrobin but their EC50, based on tests of inhibition of conidial germination, increased from 0.05 in 2002 to 0.44 μg/ml in 2008. The EC50 values based on mycelial growth inhibition for thiophanate-methyl were >162 μg/ml, 1.99 to 12.5 μg/ml, and <1.0 μg/ml for HR, LR, and sensitive isolates, respectively.