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.

Soybean rust (Phakopsora pachyrhizi) in Brazil is mainly controlled with applications of fungicides, including demethylation inhibitors (DMI) and quinone outside inhibitors (QoI). Isolates with less sensitivity to DMI and QoI have been reported, and these have been found to have mutations in the CYP51 and CYTB genes, respectively. There have been no reports of fitness costs in isolates with mutations in CYP51 and CYTB, and the aim of this work was to compare the competitive ability of isolates with lower DMI or QoI sensitivities with that of sensitive (wild-type) isolates. Urediniospores of sensitive wild-type isolates and isolates with different CYP51 or CYTB alleles were mixed and inoculated on detached soybean leaves. After 3 weeks, urediniospores were harvested and used as inoculum for the next disease cycle. Frequencies of relevant target site mutations were monitored using the pyrosequencing method over four disease cycles. Isolates with lower DMI sensitivity and different CYP51 alleles had competitive disadvantages compared with a DMI-sensitive, wild-type CYP51 isolate. In contrast, the isolate with the F129L mutation in the CYTB gene competed equally well with a QoI-sensitive, wild-type CYTB isolate under the conditions of this experiment. The CYP51 and CYTB alleles were stable in all isolates over four disease cycles when cultivated alone.

The failure of chemical control of soybean rust has been related to the selection of less sensitive isolates, and the infection capacity of such isolates could have implications for the management of the disease. The aims of the present study were to compare the sensitivity to tebuconazole and azoxystrobin and the monocycle of soybean rust using isolates of Phakopsora pachyrhizi from two soybean fields with different production systems (organic and conventional) in 2012/13 and 2013/14 seasons, and to monitor mutations in the CYP51 gene. To assess the sensitivity to tebuconazole and azoxystrobin, detached leaf tests and in vitro germination, respectively, were used. To evaluate the monocycle, detached leaves were inoculated with a urediniospore suspension and evaluated daily by counting the number of uredia. The occurrence of the mutations in CYP51 was investigated by a pyrosequencing assay. In both 2012/13 and 2013/14 seasons, the EC 50 to tebuconazole was lower for the population from the organic system (0.41 and 0.10 lg mL À1 , respectively) compared to the conventional system (1.60 and 4.44 lg mL À1 , respectively), while the EC 50 to azoxystrobin was similar for both populations. The lower sensitivity to tebuconazole and azoxystrobin was associated with F120L + Y131H mutations in CYP51, and the F129L mutation in CYTB, respectively. The monomolecular model fitted to monocycle data and parameters related to the maximum asymptote and the AUDPC were superior for organic than the conventional system.

Asian soybean rust (ASR) caused by Phakopsora pachyrhizi is the main soybean leaf disease in Brazil. Downy mildew (Peronospora manshurica) and powdery mildew (Microsphaera diffusa) are important soybean foliar diseases of occurrence in Paraná state. To reduce severity and yield losses caused by soybean foliar diseases, this work aimed to verify the efficacy of different application doses of the commercial product Dipel® Bacillus thuringiensis (Bt), which is a biological insect controller, combined with number of Opera® fungicide (pyraclostrobin + epoxiconazole) intercalated applications, and to investigate the effect of the Bt Dipel® in the resistance induction of soybean. For this study, different methodologies were used, including in vitro, in vivo and field assays. The results showed that Bt Dipel® can reduce soybean foliar diseases by inducing β-1,3 glucanase enzime and phytoalexin gliceolin. The fungicide application in the experiment condition reduced yield losses.

RESUMOObjetivou-se neste trabalho elaborar e validar uma escala diagramática para a ferrugem alaranjada da cana-de-açúcar e comparar a sua eficiência em avaliar a doença com a escala da ferrugem marrom. Para elaboração da escala foram coletadas 120 folhas de uma cultivar suscetível à doença, e a maior e menor severidades encontradas representaram os extremos da escala. Os níveis intermediários foram calculados respeitando a lei de Weber-Fechner. A escala foi proposta com nove níveis de severidade: 0,06; 0,14; 0,36; 0,89; 2,17; 5,18; 11,87; 24,92 e 45,00%. Oito avaliadores realizaram a validação estimando a severidade de 120 folhas em três avaliações: sem escala, com a escala da ferrugem marrom e com a escala da ferrugem alaranjada. A escala elaborada foi mais eficiente para avaliar a doença, proporcionando um coeficiente de determinação (R 2 ) médio de 0,91 e ausência de erros constantes e sistemáticos. Com a escala da ferrugem marrom, o R 2 médio foi de 0,84, e três avaliadores cometeram desvios constantes. Com a escala elaborada, aproximadamente 92% das estimativas estiveram na faixa de variação de 5% do valor real, enquanto que nas avaliações sem escala e com a escala da ferrugem marrom, aproximadamente 78% e 84% das estimativas, estiveram nessa faixa, respectivamente. Palavras-chave: Puccinia kuehnii, Saccharum spp., patometria, severidade. ABSTRACT Proposal and validation of diagrammatic scale for assessment of orange rust of sugarcaneThe aim of this work was to elaborate and validate a diagrammatic scale to quantify the severity of orange rust of sugarcane and to compare its efficiency in assessing the disease with the scale of brown rust. For the design of the scale, 120 sugarcane leaves were collected from a susceptible cultivar and the highest and the lowest severity founded were selected as extremes of scale. The intermediate levels were calculated according to the law of Weber-Fechner. The scale was proposed with nine levels of severity: 0,06; 0,14; 0,36; 0,89; 2,17; 5,18; 11,87; 24,92 and 45,00%. The validation was accomplished by eight appraisers who estimated the severity of 120 leaves in three assessments: without scale, with scale of brown rust and with the proposed diagrammatic scale. The scale proposed was more efficient than the scale of brown rust to assess the severity of this disease, providing an average coefficient of determination (R 2 ) of 0,91 and absence of constant and systematic errors. With the scale of brown rust, the average R 2 was 0,84 and three appraisers committed constant errors. Moreover, with the scale proposed, approximately 92% of the estimates of the appraisers had been in the range of variation of 5% of the value of real severity, while in the assessments without scale and with scale of brown rust, approximately 78% and 84% of the estimates were in that range, respectively.