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Yellow and black Sigatoka, caused by Mycosphaerella fijiensis and M. musicola, respectively, are the most important worldwide foliar diseases of bananas. Disease control is heavily dependent on intensive fungicide sprays, which increase selection pressure for fungicide resistance in pathogen populations. The primary objective of this study was to assess the level and spread of resistance to quinone-outside inhibitors (QoI—strobilurin) fungicides in populations of both pathogens sampled from banana fields under different fungicide spray regimes in Southeastern Brazil. Secondly, we aimed to investigate when QoI resistance was confirmed if this was associated with the target-site alteration G143A caused by a mutation in the mitochondrial encoded cytochrome b gene. QoI resistance was detected in fungicide treated banana fields, while no resistance was detected in the organic banana field. A total of 18.5% of the isolates sampled from the pathogens' populations were resistant to QoI. The newly described M. thailandica was also found. It was the second most abundant Mycosphaerella species associated with Sigatoka-like leaf spot symptoms in the Ribeira Valley and the highest level of QoI resistance was found for this pathogen. The G143A cytochrome b alteration was associated with the resistance to the QoI fungicides azoxystrobin and trifloxystrobin in M. fijiensis, M. musicola and M. thailandica strains. In order to reduce resistance development and maintain the efficacy of QoI fungicides, anti-resistance management strategies based on integrated disease management practices should be implemented to control the Sigatoka disease complex. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Black Sigatoka disease caused by Mycosphaerella fijiensis is the most severe banana disease worldwide. The pathogen is in an invasive phase in Brazil and is already present in most States of the country. The potential of 29 isolates of Trichoderma spp. was studied for the control of black Sigatoka disease under field conditions. Four isolates were able to significantly reduce disease severity and were further tested in a second field experiment. Isolate 2.047 showed the best results in both field experiments and was selected for fungicide sensitivity tests and mass production. This isolate was identified as Trichoderma atroviride by sequencing fragments of the ITS region of the rDNA and tef-1α of the RNA polymerase. Trichoderma atroviride was as effective as the fungicide Azoxystrobin, which is recommended for controlling black Sigatoka. This biocontrol agent has potential to control the disease and may be scaled-up for field applications on rice-based solid fermentation. [ABSTRACT FROM AUTHOR]

Fungal disease epidemics have the potential to bring about drastic innovations. However, in the case of the Black Sigatoka ( Mycosphaerella fijiensis) fungus in bananas, producers and international traders are still awaiting a breakthrough in crop protection research. Using the cases of Brazil and Colombia, this paper examines different agricultural research responses to the disease. Brazil opted to replace susceptible varieties with resistant ones, whereas in Colombia chemical control by private actors dominated. We argue that these different responses result from at least three interrelated factors. First, producer type-smallholder farmers or larger export-oriented plantations-influences the setting of crop protection research priorities. Second, a central, state-led role versus a private sector response influences the size and time perspective of research activities. Third, domestic markets with multiple crop varieties versus Cavendish-only export markets leads to differences in control practices and research responses. From this case study, we argue that the currently proposed innovation systems approaches in international agricultural research should adopt a broader perspective that assesses how research is interwoven with agrarian dynamics, commodity chains and particular state roles to elucidate how state-producer-researcher networks perform disease control and where and how to find new solutions. [ABSTRACT FROM AUTHOR]

Eleven primers RAPD were used to estimate the genetic variability between 31 isolates of M. musicola collected from 'PrataAnã' and Nanica bananas that were cultivated in northern Minas Gerais, Brazil. A total o 83 fragments were amplified, of which 73 were polymorphic, corresponding to an average of 6.6 polymorphic fragments per primer. The genetic distances ranged from 0.06 to 0.56 and the average distance of 0.21. A dendrogram constructed based on the UPGMA clustering method revealed 8 and no correlation between molecular grouping and geographical origin was observed. [ABSTRACT FROM AUTHOR]

Leaf blight and defoliation caused by Teratosphaeria species is one of the most important leaf diseases of Eucalyptus globulus. Due to the importance of this tree species for the production of pulp and paper, and recent reports of severe leaf disease symptoms in Brazil, the present study was conducted to identify the pathogen(s) involved. Symptomatic leaves were collected in the Brazilian states of Paraná and Rio Grande do Sul, single ascospore cultures established, and isolates were investigated using DNA-based molecular tools. A species-specific PCR and sequence data from the nuclear ribosomal DNA operon were used for species identification. The following seven species were identified: Mycosphaerella scytalidii, Dissoconium dekkeri (=M. lateralis), Teratosphaeria ohnowa, T. perpendicularis, T. pseudafricana, T. flexuosa and T.nubilosa. Of the recorded species, T. nubilosa is regarded as the most serious threat to the cultivation of E. globulus in the states surveyed. [ABSTRACT FROM AUTHOR]

Weather conditions make the Recôncavo Region in the State of Bahia, a favorable region to the occurrence of citrus greasy spot (Mycosphaerella citri), a disease that hadn't been studied before in Brazil. Thus, this research aimed to develop a sampling method to quantify its incidence, to characterize its symptoms, and to develop a diagrammatic scale for assessing disease severity. The minimum sample size to estimate greasy spot incidence in leaves (16 plants) was calculated based on a prospective sampling of five leaves per quadrant, four quadrants per tree, and 30 trees per grove, in ten groves. From 320 mature leaves collected in different plants of 11 groves, it was observed a high number of lesions per symptomatic leaf (mean of 131±102), most of them small (mean of 0.014±.,011cm2). Greasy spot severity varied from 0,15% to 35,85%, with a mean of 7,3%. Based on those severity values, a six level (1%, 2%, 5%, 9%, 18% e 36% of lesioned leaf area) diagrammatic scale was developed. 50 images of symptomatic leaves were showed to evaluators, which estimated the severity with and without the use of the scale. The diagrammatic scale use, slightly increased the estimates accuracy and precision. [ABSTRACT FROM AUTHOR]

Evidence of the teleomorph Mycosphaerella graminicola (Fuckel) Schroeter (anamorph: Septoria tritici Rob. apud Destn.) in the Federal Republic of Germany Due to the fullfillment of certain biological requirements, the dominant occurrence of Septona tritici is restricted mainly to the milder climate of maritime regions. However, following mild winters in continental climatic zones, an increased and yield damaging appearance, which is additionally influenced by early sowing dates, can be observed. Previous proofs of the teleomorph Mycosphaerella graminicola (Fuckel) Schroeter were found in Australia, Brazil, Great Britain, Chile and the USA. With the first proof of teleomorph in Bavaria and herewith the complete life cycle, the optimum mechanism for an early and widespread primary infection of young wheat plants has been confirmed. [ABSTRACT FROM AUTHOR]