The genetic structure of Mycosphaerella musicola has never been investigated in Brazil to address epidemiologically related questions associated with yellow sigatoka. A total of 223 single‐conidium isolates from four regions (North, South, Zona da Mata and Triângulo Mineiro) of Minas Gerais State, Brazil, were used to assess the population genetic structure of M. musicola. Isolates were characterized regarding the frequency of the MAT1‐1‐1 or MAT1‐2‐1 idiomorphs and polymorphism at nine microsatellite loci. The mating‐type ratio in three of the four subpopulations was c. 1:1. A total of 87 alleles and 216 multilocus genotypes were identified. The overall population was in linkage equilibrium. Most (93.9%) genetic variation was detected within the subpopulations and there was weak differentiation between them. In total, eight genetic groups were detected and isolates of seven groups were present in all regions. The population of M. musicola in Minas Gerais seems to have high evolutionary potential: it is panmictic and both sexual reproduction and gene flow affect genetic variability. Strategies to avoid fungicide resistance should be enforced and breeding programmes need to consider quantitative resistance in the banana cultivars.

Moniliophthora perniciosa, causal agent of witches' broom disease in cacao plantations in South America and the Caribbean Islands, has co-evolved with its host cacao, but the pathogen has also emerged in many solanaceous hosts in Brazil, including economically important food crops and wild species. This study was carried out to: (i) determine the existence of host subpopulations of M. perniciosa in Brazil; (ii) estimate gene and genotypic diversity of M. perniciosa host subpopulations infecting solanaceous hosts in southeastern Bahia and Minas Gerais states, Brazil; and (iii) estimate the amount and directionality of historical migration of M. perniciosa subpopulations. Up to 203 M. perniciosa isolates collected from solanaceous hosts with symptoms from Bahia and Minas Gerais states in Brazil and from Theobroma spp. (cacao) and Herrania spp. were characterized with 11 microsatellite markers. Factorial correspondence analyses, minimum-spanning network and Bayesian clustering revealed genetic clusters associated with their host of origin. Significant subpopulation differentiation was evident (Φ ST = 0.30, P ≤ 0.05) among M. perniciosa host subpopulations. Most of the multilocus microsatellite genotypes (MLMGs) were host-specific, with few MLMGs shared among subpopulations. Pairwise comparisons among M. perniciosa host subpopulations were significant, except between jurubeba (Solanum paniculatum) and cultivated solanaceous subpopulations. The combined analyses rejected the null hypothesis that M. perniciosa in Brazil is a single genetic population not structured by host. These findings support a scenario of introduction and subsequent adaptation to solanaceous hosts that should be taken into consideration to improve mitigation and management of M. perniciosa.

A thorough assessment of the distribution of Mycosphaerella spp. associated with banana in Minas Gerais State, Brazil, was conducted after Mycosphaerella fijiensis was first reported to occur in this region in 2005. From 2009 to 2011, 80 fields located in 20 municipalities including the same fields where the disease was first reported were sampled. A total of 800 samples of leaf tissue with symptoms similar to those of yellow or black Sigatoka diseases were examined, and 239 isolates were obtained. The identification of the fungi was based on morphological characters combined with DNA sequences obtained after amplification with species-specific primers and phylogeny inferred from the internal transcribed spacer region of Mycosphaerella strains from banana. All 239 isolates were identified as Mycosphaerella musicola. The absence of M. fijiensis in the samples may have been due to misidentification of M. fijiensis or the displacement of M. fijiensis by M. musicola. It is now apparent that yellow Sigatoka caused by M. musicola is the prevailing leaf spot disease of bananas in Minas Gerais State and that regulatory/legislative control measures need to be revised based on our findings.

Black Sigatoka caused by Mycosphaerella fijiensis is a foliar disease that affects banana plants and large amounts of fungicides are required to prevent crop losses. Intensive applications of single-site fungicides can select for fungicide-resistant isolates. The objective of this study was to assess the sensitivity of 60 isolates of M. fijiensis to commonly used fungicides. Using two different protocols, microtiter and Petri plate tests, the effective concentration at which mycelium growth is reduced by 50% (EC 50 ) was determined for thiophanatemethyl, tebuconazole, chlorothalonil and mancozeb. Additionally, partial sequences of the cytochrome b gene were obtained for 46 isolates to detect the G143A mutation, commonly associated with strobilurin resistance. The EC 50 values for tebuconazole and thiophanate-methyl ranged from 0.02 to 1.39 and from 0.008 to 8.22 μg mL -1 , respectively. For chlorothalonil, the lowest and highest EC 50 values were 0.39 μg mL -1 and 53.7 μg mL -1 , respectively. For mancozeb, approximately 50% of the isolates had EC 50 values greater than 1000 μg mL -1 . No mutation was found in the isolates assayed for strobilurin resistance. There was no correlation between sensitivity levels to any fungicide and geographic region. Low EC 50 values were estimated for most fungicides but, some isolates had high EC 50 values for mancozeb.