Carolina Cardoso Deuner

Limiares térmicos para a germinação de conídios de Cercospora sojina em dois regimes luminosos

The aim of this study was to evaluate the germination of exposure time of 3 hours, the best germination occurred at a Cercospora sojina conidia at different temperatures under continuous temperature of 23.8 oC, for 6 hours at 24.3 oC, for 9 hours at 22.9 oC light and in the dark in order to determine the lower and the upper and for 12 hours at 22.4 oC. When the plates were incubated in the temperature threshold, as well as the optimum temperature. Conidia dark, conidium germination was greater when exposure time was 3 were deposited on the surface of Petri plates containing agar-water hours at a temperature of 23.8 oC 6 hours at 23.4 oC, 9 hours at 22.9 substrate. They were then incubated in BOD under continuous light oC and 12 hours at 22.7 oC. The optimum temperature for conidium and in the dark at different temperatures (0; 5; 10; 15; 20; 25; 30; 35 germination under continuous light was 22.4 oC and in the dark it was and 40 oC) and withdrawn at different exposure times (3, 6, 9 and 12 23 oC, while the lower temperature threshold was 0 oC and the upper hours). For C. sojina conidia subjected to continuous light for the threshold was 40 oC.

Sensibilidade do método de obtenção das células bacterianas e da técnica de PCR para detecção de Curtobacterium flaccumfaciens pv. flaccumfaciens em sementes de feijão

Currently, there is a need to develop sensitive methods, inexpensive, reproducible and rapid detection of phytobacteria seeds. The objective of this study was to optimize a method for obtaining bacterial cells and the PCR technique to detect Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff), in bean seeds using PCR. It was used one pairs of primers CffFOR2-REV4, designed from an PCR amplified fragment of the conserved repetitive sequence (Rep-PCR). The primer pair CffFOR2-REV4 was selected in this study, because demonstrated higher reproducibility and efficacy in the detection of Cff strains in bean seeds. Four methods were also evaluated in the seed extract preparation for PCR: 1) rough seed extract; 2) millipore membrane filter (0.22Mu diameter) concentrated seed extract and subsequently ressuspended in water; 3) centrifuge concentrated seed extract 10.000 xg for 15 minutes for 20 and 80 mL; 4) Bio-PCR. Among those methods, either Bio-PCR or centrifuge concentrated extract, in a total 20 or 80 mL suspension volume, produced a 306bp DNA fragment, diagnostic for Cff. Those two techniques detected the bacterium and presented high sensitivity, detecting up to 1 Cff physiological conditioning artificially contaminated seed in a total 999 healthy ones. A total of seventeen commercial bean seed lots were analyzed by the method of concentration of the extract by centrifugation, and twelve detected in the bacterium Cff, observed by the presence of bands with 306 bp. Therefore, it was possible to optimize a method of obtaining the bacterial cells and PCR for detection of Cff in bean seeds, that is sensitive, reproducible and easy to perform, which can be used routinely in laboratories for seed.

Inoculação de Curtobacterium flaccumfaciens pv. flaccumfaciens em sementes de feijão por meio da técnica de condicionamento fisiológico

This study used the physiological conditioning technique in an agar-based medium for Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff) to inoculate dry beans. The seed performance of the Perola dry bean variety was evaluated after submitting it to physiological conditioning in a water restricted agar-based medium. The treatments consisted of exposing dry bean seeds to the bacteria for different time periods at four levels of water restriction in 523 medium (-0.55, -0.75, -0.95 and -1.15 MPa), and four substrates (523 medium, 523 medium+KCl, 523 medium+mannitol and 523 medium+sucrose) with an additional control treatment of 523 medium without any osmotic restriction (-0,55 MPa). After each time period, the number of germinated seeds in the medium was evaluated and the water content, germination and seed enzymatic patterns were assessed. In a second study, growth was assessed for four Cff strains (Cff DF - Feij-2936, Cff PR - 12768, Cff SC - Feij-2928 e Cff SP - Feij-2634) in different water restriction 523 media. The treatments in the third phase were defined on the basis of the results of the first stage, where the best combination was mannitol-amended 523 medium set for -0,95 MPa water potential and 48 hours exposure to the pathogen. In the second phase, the Cff SC (Feij-2928) strain from Santa Catarina state showed the best growth in an agar-based medium and water potential as defined in the first phase. Thus, Cff artificial inoculation in bean seeds was done by using the physiological conditioning technique in an agar-based medium without the occurrence of any detectable changes in the seed physiological quality patterns.

In vitro Determination of Fungicide Inhibitory Concentration for Phakopsora pachyrhizi isolates

In vitro assays were preformed to obtain the IC50 of eight fungicides against Phakopsora pachyrhizi isolates from Passo Fundo, RS, Ponta Grossa, PR, and Primavera do Leste, MT. Different concentrations of the fungicides were added to Petri dishes containing soybean leaf extract agar medium. One milliliter of P. pachyrhizi uredospore suspension at the concentration of 3.0 x 104 uredospores/mL was added to each dish for subsequent viability quantification. Only pyraclostrobin and the mixture trifloxystrobin + prothioconazole showed IC50 values inferior to 1.0 mg/L for all tested isolates, demonstrating high fungitoxicity. There was not loss of sensitivity to any of the tested fungicides.

Inoculum production and evaluation of temperature and leaf wetness for Passalora sojina inoculation in soybean

Postgraduate student in Agronomy at University of Passo Fundo, Passo Fundo, Rio Grande do Sul, 99052-900, Brazil. ju_camera@yahoo.com. br; Professor at University of Passo Fundo, Passo Fundo, Rio Grande do Sul, 99052-900, Brazil. Researcher at OR Seeds, Passo Fundo, Rio Grande do Sul, 99050-380, Brazil. erleireis@upf.br; Professor at University of Cruz Alta, Cruz Alta, Rio Grande do Sul, 98020-290, Brazil. jkoefender@unicruz.edu.br. Autor para correspondência. Carolina Cardoso Deuner (carolinadeuner@gmail.com). Data de chegada: 30/08/2016. Aceito para publicação em: 11/04/2017. 10.1590/0100-5405/168573

Influence of continuous cropping on corn and soybean pathogens

ABSTRACT The objective of this study was to evaluate the influence of two tillage programs (conventional and no-tillage) and different rotations with soybeans and corn on the occurrence of Fusarium species. The work was conducted in the experimental field and Seed Laboratory at Iowa State University. The treatments were: tillage (no-tillage and conventional tillage), crop (corn and soybeans) and three different cropping sequences for corn and soybeans, respectively. Treatment with corn: (1) the first year after four years of soybeans (1C); (2) alternating corn and soybeans each year (C / SB); (3) Continuous corn (C). Treatment with soybeans; (1) the first year after four years of corn (1S); (2) alternating soybeans and corn each year (SB / C); (3) Continuous soybeans (S). Two plant counts were performed in two stages in soybean (VC and V3) and corn (V1 and Ranzi, C.; Camera, J.N.; Deuner, C.C. Influence of continuous cropping on corn and soybean pathogens. Summa Phytopathologica, v.43, n.1, p.14-19, 2017.

Resistência de cultivares de trigo à giberela mediante inoculação artificial em espiguetas

This study aimed to determine the optimal concentration of F. graminearum conidia for artificial inoculation in wheat spikelets and to verify the type of head blight resistance (Type I and / or II) in wheat cultivars. The study consisted of two experiments, and in the first one, the optimal concentration of conidia mL-1 was determined for artificial inoculation in four cultivars. Thus, the tested concentrations were 5x103, 15x103, 25x103, 35x103and 40x103 conidia mL-1. Twenty-one days after inoculation, the incidence of F. graminearum in spikelets was quantified, and regression analysis was used to determine the optimal concentration of conidia ml-1 for each cultivar. In the second experiment, the resistance of wheat cultivars to artificially inoculated head blight was evaluated, using the same methodology adopted in the previous experiment and the concentration of 31x103 conidia mL-1. The evaluated variables were severity, affected grains and incidence in affected spikelets. The best concentration for artificial inoculation of head blight in wheat spikelets is 31x103 conidia mL-1. The greatest severity of the disease was observed for wheat cultivars BRS 208 and Pampeano, and the highest percentage of affected grains was noted for BRS 208. The cultivars Pampeano and BRS 177 did not show Type I resistance to head blight but had Type II resistance, while the cultivars Mirante and BRS 208 had neither of the resistance types.

Efeito de temperaturas na expansão, número de lesões e severidade da mancha-amarela da folha do trigo

Tan spot of wheat, caused by the fungus Pyrenophora tritici-repentis, anamorphic form Drechslera tritici-repentis, is one of the major diseases affecting this crop. The lesion expansion is an important component of this epidemic and, similarly to others, can be influenced by temperature. Therefore, the aim of this study was to evaluate the effect of temperature on the expansion and number of lesions, as well as on the severity of tan spot of wheat. The study was conducted in climatic chambers at five temperatures (10, 15, 20, 25 and 30°C) with the cultivars Mirante and Fundacep Horizonte. Plants were inoculated, in the stage of three expanded leaves, with 3x103conidia/ml suspension in water. The lesions were measured at every three days from the onset of symptoms. In addition, lesions were counted per leaf and severity scores were estimated. The adopted design was in randomized block with four replicates, and each pot constituted a replicate. Temperature positively influenced the disease increase, and at 30°C the number and progress of lesions, as well as the severity of the disease, were greater.

Etiology of phomopsis root rot in soybean

Em levantamento de danos causados por podridoes radiculares da soja, em lavouras do sul do Brasil durante varios anos, tem sido encontrado com maior frequencia uma podridao radicular causada por Phomopsis sp. Os sintomas primarios sao visualizados quando se corta longitudinalmente a raiz principal, observando-se a morte do lenho ostentando coloracao branca, com linhas negras bem definidas, sem um formato definido. Por isso, por semelhanca, tem sido chamada de podridao radicular de geografico, pelo aspecto que lembra as linhas irregulares separando regioes num mapa. Isolamentos foram feitos durante varias safras e feita a prova de patogenicidade. Nos isolamentos tem predominado colonias e os esporos alfa de Phomopsis sp. A prova de patogenicidade foi feita pela inoculacao no colo de plantas cultivadas em câmara de crescimento. Reproduziram-se os sintomas de geografico nas plantas e foi reisolado o fungo Phomopsis sp. Em hastes de soja naturalmente infectadas pela seca-da-haste e da-vagem sao encontrados sintomas de geografico causados por Phomopsis phaseoli. Aos sintomas conhecidos em hastes, vagens e graos acrescenta-se agora o de podridao radicular causada por P. phaseoli.

Agressividade de três raças de Cercospora sojina em folhas de soja

Aggressiveness of three races of Cercospora sojina in soybean leaves This study aimed to evaluate the pathogenicity and aggressiveness of three races of C. sojina to the soybean cultivars Bragg and BMX Magna. A conidial suspension was prepared in the concentration of 40 x 10 3 conidia mL -1 for plant inoculation. Fifteen days after inoculation with the fungus, no statistical difference was found among cultivars for severity and number of lesions per leaflet for race 23. Races 24 and 25 caused the highest infection in cv . BMX Magna , significantly different from cultivar Bragg. Alpha Lesion diameter for race 23 was larger in cv. Bragg and for race 24 was larger in cv. Magna BMX, but for race 25 there was no statistical difference between the cultivars. Therefore, the races of C. sojina are pathogenic to the two soybean cultivars and there is difference in aggressiveness among them, with the races 24 and 25 being more aggressive than race 23.