ABSTRACT This study aimed to identify the correlations between traits of the groups stem cutting, seedling, stem, and root of cassava. Length, diameter, and weight of stem cutting (Group 1) were measured at each growing season (July, August, September, and October). A total of 300 cuttings were collected after sprouting and planted at seasons of September 22, October 7 and 19, and November 25. Plant height at planting, number of leaves at planting, and number of leaves at 7 days after planting were measured. The number of leaves at transplanting and plant height at transplanting were determined after acclimation (Group 2). Seedling transplanting was carried out on November 9 and 24 and December 3 and 26, and the traits stem (Group 3) and root (Group 4) yield were measured at harvest. Associations between the groups stem cutting and seedling were established by stem cutting diameter and weight, and height and number of leaves at planting. Seedling traits had the greatest influence on the number of buds per stem and stem diameter. Main stem branching height and stem diameter can be used for selecting plants with an indication of the best quality and yield of root traits.

Abstract In agricultural experiments, measuring all plants that constitute an experimental unit is the most appropriate method for estimating averages. This study analyzed sample sizes (number of plants) for estimating averages of agronomic traits in cassava. The experiment for seedling production was conducted on four sowing dates: September 22, October 7, October 19, and November 25, 2017. The evaluated characters were plant height at planting, number of leaves at planting, number of leaves at 7 days after planting, number of leaves at transplanting, and plant height at transplanting. The seedlings were transplanted to the field on November 9, November 24, December 3, and December 26. Root characteristics and root yield were measured at harvest. The following statistics were measured: minimum, maximum, range, mean, median, variance, standard deviation, and coefficient of variation. The sample size was determined by resampling with replacement when the range of the 95% confidence interval (CI) was 10%, 20%, 30%, and 40% of the average estimate. Larger sample sizes were needed to estimate trait averages with a 95% CI range of 10% of the average estimate, i.e., when estimation accuracy was higher. In contrast, lower sample sizes were required to estimate averages of all characters in all planting times with a 95% CI range of 40%. For measuring seedling production and stem and root yield, 63 and 153 plants are sufficient to estimate averages when the range of the 95% confidence interval was 20%.

Resumen En experimentos agrícolas, medir todas las plantas que constituyen una unidad experimental es el método más apropiado para estimar promedios. Este estudio analizó tamaños de muestra (número de plantas) para estimar promedios de caracteres agronómicos en yuca. El experimento para la producción de plántulas se realizó en cuatro fechas de siembra: 22 de septiembre, 7 de octubre, 19 de octubre y 25 de noviembre de 2017. Los caracteres evaluados fueron la altura de la planta en la siembra, el número de hojas en la siembra, el número de hojas a los 7 días después de la siembra, el número de hojas en el trasplante y la altura de la planta en el trasplante. Las plántulas se trasplantaron al campo el 9 de noviembre, 24 de noviembre, 3 de diciembre y 26 de diciembre. Las características de la raíz y el rendimiento de la raíz se midieron en la cosecha. Se midieron las siguientes estadísticas: mínimo, máximo, rango, media, mediana, varianza, desviación estándar y coeficiente de variación. El tamaño de la muestra se determinó mediante remuestreo con reemplazo cuando el rango del intervalo de confianza (IC) de 95% fue de 10%, 20%, 30% y 40% de la estimación promedio. Se necesitaron tamaños de muestra más grandes para estimar los promedios de rasgos con un rango de IC de 95% de 10% de la estimación promedio; es decir, cuando la precisión de la estimación fue mayor. En contraste, se requirieron tamaños de muestra bajos para estimar promedios de los caracteres en los tiempos de siembra con un rango de IC de 95% de 40%. Para medir la producción de plántulas y rendimiento de tallos y raíces, 63 y 153 plantas son suficientes para estimar promedios cuando el rango del intervalo de confianza de 95% fue de 20%.

ABSTRACT Chia is a plant whose seeds are used in cooking and is a natural source of omega-3 fatty acids, fiber and protein, as well as other important nutritional components such as antioxidants. The objective of this work was to estimate the base temperature, plastochron and chia seed yield for different sowing times in Cruz Alta, Rio Grande do Sul, Brazil. The experimental design was completely randomized and the treatments consisted of different sowing times (September, October and November). For the determination of the base temperature for node emission in the main stem of the plants, the method of least mean square error of linear regression between the number of nodes and the accumulated thermal sum was used. Regarding estimation of the plastochron at each sowing time, a simple linear regression was obtained between the number of nodes in the main stem and the accumulated thermal sum. Seed yield was measured at harvest. Sowing in times with air temperature below 19 ºC should be avoided so that the development of plants is not impaired. Plastochron ranges from 28.01 ºC to 32.26 ºC day for successive node emission in the main stem of chia plants and September sowing promotes higher seed yield.

ABSTRACT. A study was conducted during four growing seasons to investigate the rooting capacity and survival percentage of cassava seedlings from stem cuttings selected based on their number of leaves. The experimental design was a randomized block design with five replications in a factorial scheme (4 × 2 × 2), totalling 16 treatments. Treatments consisted of combinations of growing season (September 22, October 7 and 19, and November 25), stem cuttings smaller (15 to 19.99 mm) and larger (20 to 25 mm) than 20 mm in diameter, and number of leaves on the stem cuttings (3 to 5 and 6 to 8 leaves). The experiment was carried out during the four growing seasons in a Van der Hoeven greenhouse. The greenhouse, as well as the benches on which the treatments were placed, had a north-south orientation. The greenhouse has an automatic mist irrigation system, and the mean temperature was 25 °C. The plant height at planting, number of leaves at planting, and number of leaves at 7 days after planting were measured. The final number of leaves, final plant height, shoot dry matter, root dry matter, and total dry matter were measured after acclimatization. Stem cuttings between 20 and 25 mm in diameter should be used to produce cassava seedlings with the rapid multiplication method. Cuttings with 6 to 8 visible leaves should be collected, and the cuttings should be planted at the end of September.

ABSTRACT Physalis angulata L. is a plant with great fruit production potential, mainly in family farms, due to its versatility and valuable products such as jellies and juice concentrates. The aim of the present study is to evaluate the effect of two cytokines - i.e., plant growth regulators 6- benzylaminopurine (BAP) and kinetin (KIN) -, in association, or not, with auxin (2,4-dichlorophenoxyacetic acid - 2.4-D), on P. angulata multiplication in vitro. The experiment followed a completely randomized design, with eighteen treatments and five repetitions, based on factorial arrangement 2 x 5 x 2. Cytokinin sources were used at concentrations: 0, 2.5, 5.0, 7.5 and 10 mg L-1; in the presence (0.05 mg L-1) or absence of 2.4-D. Explants comprised nodal segments (approximately 1 cm) deriving from Physalis seed germination in vitro. Results indicate that the growth regulator KIN, at 5 mg L-1 concentration and in the absence of auxin 2.4-D, has potential to enable longer shoot length and larger number of internodes. However, the culture medium (MS) without plant growth regulators recorded higher biomass (fresh and dry weight) and increased root rate.

RESUMO A helmintosporiose está entre as principais doenças da cultura do milho. Realizou-se dois ensaios com os objetivos de avaliar a esporulação do fungo diferentes meios de cultura, métodos de inoculação e concentrações de inóculo para Exserohilum turcicum. Para a esporulação em diferentes meios de cultura, testou-se seis diferentes substratos: batata sacarose ágar (BSA), extrato de folha de milho (FM), potato dextrose ágar (PDA), suco V8 ágar (V8), lactose caseína hidrolisada ágar (LCHA) e meio semi-seletivo De Rossi e Reis (DRR) submetidos a dois regimes luminosos, fotoperíodo de 12 e escuro contínuo. E no segundo ensaio avaliou-se dois métodos de inoculação: a aspersão e a deposição do inóoculo no cartucho das plântulas, sendo testadas as concentrações de 5x103, 10x103, 15x103 20x103, 25x103 conídios/mL, e para o segundo foram depositados 0,5 mL na concentração de 20x103 conídios/mL nos cartuchos. Para ambos os métodos a inoculação foi feita no estádio V4 (quarta folha expandida, apresentando colar, lígula e aurículas visíveis), e mantidos em câmara úmida por 24 horas na temperatura de 25 0C. Quinze dias após a inoculação, avaliou-se a severidade estimada e a área da lesão. O delineamento experimental foi inteiramente casualizado com quatro repetições e os dados obtidos foram submetidos à análise de variância e de regressão. O maior número de conídios.cm-2 foi obtido no meio DRR, independente do regime luminoso. O método de aspersão mostrou-se eficaz nas concentrações de 15x103, 20x103 e 25x103 conídios/mL

ABSTRACT Helminthosporiosis is among the major corn diseases. Two experiments were carried out with the aim of evaluating fungal sporulation in different culture media, inoculation methods and inoculum concentrations for Exserohilum turcicum. For sporulation in different culture media, six different substrata were tested: potato sucrose agar (BSA), maize leaf extract (FM), potato dextrose agar (PDA), V8 juice agar (V8), lactose casein hydrolysate agar (LCHA) and semi-selective medium De Rossi and Reis (DRR) subjected to two light regimes, 12 hours photoperiod and continuous dark. In the second assay, two inoculation methods were evaluated: spray and deposition of the inoculum in the seedling cartridge, testing the concentrations of 5x103, 10x103, 15x103 20x103, 25x103 conidia / mL, and in the second one, 0.5 mL at the concentration of 20x103 conidia/mL were deposited in the cartridges. For both methods, inoculation was done in stage V4 (fourth expanded leaf, showing collar, ligule and visible auricles) and kept in a humid chamber for 24 hours at the temperature of 25 0C. Fifteen days after inoculation, the estimated severity and the lesion area were evaluated. The experimental design was completely randomized with four replicates, and data were subjected to analysis of variance and regression. The highest number of conidia.cm-2 was obtained in the DRR medium, independent of the light regime. The spray method was effective at the concentrations of 15x103, 20x103 and 25x103 conidia/mL.

ABSTRACT Nematodes of the genus Meloidogyne are associated with soybean cultivation, unknown the reaction of cultivars. The objective of this work was to determine the reaction of soybean cultivars to M. javanica and M. incognita. Twenty-seven soybean cultivars were sown in plastic pots, in a completely randomized experimental design with eight replicates. Ten days after emergence of the seedlings, in a separate experiment, M. javanica and M. incognita were inoculated. For M. javanica, cultivars classified as susceptible were BMX Lança IPRO, AMS Tibagi RR, BMX Vanguarda IPRO, NS 6700 IPRO, BMX Ativa RR, FPS Solimões RR, TEC 6702 IPRO, NS 5909 RR, NS 5445 IPRO, 54i52 RSF IPRO, M 6410 IPRO and NS 5959 IPRO and BMX Elite IPRO, NA 6211 RR, BMX Valente RR, FPS Júpter RR, FPS Iguaçú RR, BMX Tornado RR, GMX Cancheiro RR, TMG 7161 IPRO, TMG 7062 IPRO, FPS Solar RR, M 5730 IPRO, DM5958 RSF IPRO, NS 6006 IPRO, SYN 1163 RR and M 5947 IPRO were resistant. Regarding M. incognita, the resistant cultivars were FPS Iguaçú RR, FPS Solar IPRO, SYN 1163 RR and TMG 7062 IPRO. The cutlivars FPS Júpter RR, SYN 1163 RR e TMG 7062 IPRO were resistant to both nematodes.

RESUMO: A helmintosporiose e a ferrugem comum estão entre as principais doenças fúngicas que afetam a produção do milho. Os objetivos desse trabalho foram avaliar a suscetibilidade de dez híbridos de milho a helmintosporiose e a ferrugem comum e verificar a eficiência de fungicidas no controle de Exserohilum turcicum. No primeiro experimento utilizaram-se os híbridos Pioneer (30F53, P1630H, P2530), Monsanto (AG 8045, AG 9045), Dow AgroSciences (2A550, 2A106 e 2B587) e Syngenta (SYN7205 VIPTERA, SW 3949 TL), e no experimento de eficiência de fungicidas no controle de helmintosporiose, testou-se a eficiência dos fungicidas propiconazol, azoxistrobina, ciproconazol + azoxistrobina, protioconazol + trifloxistrobina, benzovindiflupir + azoxistrobina, ciproconazol + azoxistrobina + mancozebe, no híbrido Pioneer P1630H. Em ambos os experimentos avaliaram-se a severidade foliar das doenças (%), o rendimento e o peso de mil sementes. O delineamento experimental foi em blocos ao acaso com quatro repetições. Os híbridos SYN7205, P2530, SW 3949 TL, 2B587, AG 9045, 2A550, P1630H, 2A106 e AG 8025 apresentam as menores áreas abaixo da curva de progresso de severidade de ferrugem comum. Os híbridos AG9045, 30F53 e 2A550 apresentam as menores áreas abaixo da curva de progresso de helmintosporiose. Os híbridos AG8025, 2B587, P1630H, AG9045, 2A106 e 2A550 apresentam os maiores rendimentos. Os fungicidas protioconazol + trifloxistrobina apresentam a maior eficiência de controle químico de helmintosporiose e a menor AACPD.

ABSTRACT: Northern corn leaf blight (NCLB) and common rust are among the primary fungal diseases affecting maize production. This study aimed to evaluate the susceptibility of ten maize hybrids to NCLB and to common rust and to verify the efficiency of fungicides in the chemical control of Exserohilum turcicum. In the first experiment, hybrids Pioneer (30F53, P1630H, P2530), Monsanto (AG 8045, AG 9045), Dow AgroSciences (2A550, 2A106 and 2B587) and Syngenta (SYN7205 VIPTERA, SW 3949 TL) were used and in the experiment for effectiveness of fungicides in the control of NCLB. The efficiency of fungicides propiconazole, azoxystrobin, cyproconazole + azoxystrobin, prothioconazole + trifloxystrobin, benzovindiflupir + azoxystrobin, cyproconazole + azoxystrobin + mancozeb were tested in the Pioneer P1630H hybrid. In both experiments, the leaf disease severity (%), yield and the weight of one thousand seeds were evaluated. The experimental design was carried out in randomized blocks with four replicates. The hybrids SYN7205, P2530, SW 3949 TL, 2B587, AG 9045, 2A550, P1630H, 2A106 and AG 8025 showed the smallest areas under the common rust severity progress curve. Hybrids AG9045, 30F53, and 2A550 presented the smallest areas under the NCLB progress curve. Hybrids AG8025, 2B587, P1630H, AG9045, 2A106, 2A550, present the highest yields. The fungicides prothioconazole + trifloxystrobin present the highest chemical control efficiency for NCLB and the lowest area under the disease progress curve (AUDPC).

RESUMO O objetivo desse trabalho foi desenvolver uma metodologia para produção de inóculo e inoculação de Passalora sojina em soja visando avaliar a reação à mancha foliar “olho-de-rã”. Para isso foi quantificada a esporulação de raças do fungo em cinco substratos, sob dois regimes luminosos. Também foi determinada a temperatura e duração do período de molhamento foliar que resultasse na maior eficiência da infecção. Placas de Petri com os meios de cultura Farinha de Aveia Ágar (FAA), Suco de Tomate Temperado (STT), Suco V8 ágar (V8), Alimento Infantil (AI) e Batata Sacarose Ágar (BSA) contendo isolados das raças de P. sojina 23, 24 e 25 foram submetidas aos fotoperíodos de 12 h e 24 h de escuro contínuo. Plantas inoculadas foram incubadas a temperaturas de 15, 20, 25, 30 e 35 ºC e períodos de molhamento foliar de 12, 24, 36, 48 e 72 h. O delineamento experimental foi inteiramente casualizado com cinco repetições. Houve interação entre isolado, meio de cultura e fotoperíodo. A maior esporulação (conídio/cm2) foi obtida no meio de cultura STT (raça 23) e no meio V8 (raças 24 e 25), sob fotoperíodo de 12 h. A temperatura ótima para o desenvolvimento da doença foi de 27 oC com 72 horas de molhamento foliar contínuo.

ABSTRACT The objective of this study was to develop a methodology for inoculum production and inoculation of Passalora sojina in soybean to assess the reaction to frogeye leaf spot. Thus, sporulation of fungal races was quantified in five substrates under two light regimes. The temperature and the leaf wetness period that resulted in greater infection efficiency were also determined. Petri dishes containing the culture media Oat Flour Agar (OFA), Tomato Juice (FTJ), V8 agar juice (V8), Infant Food (IF) and Potato Sucrose Agar (PSA) plus isolates of P. sojina races 23, 24 and 25 were subjected to 12-h photoperiod and 24-h continuous dark. Inoculated plants were incubated at temperatures of 15, 20, 25, 30 and 35 ºC and leaf wetness periods of 12, 24, 36, 48 and 72 hours. Experimental design was completely randomized with five replicates. There was interaction among isolate, culture medium and photoperiod. The highest sporulation (conidia/cm2) was obtained in the culture media FTJ (race 23) and V8 (races 24 and 25) under 12-h photoperiod. The optimum temperature for the disease development was 27oC under 72 hours of continuous leaf wetness.

RESUMO O milho (Zea mays L.) é cultivado em todo o Brasil e apresenta grande importância econômica, dentre as doenças que causam redução na produtividade está a helmintosporiose. O objetivo deste trabalho foi avaliar a germinação de conídios do agente causal da helmintosporiose, Exserohilum turcicum, em diferentes temperaturas e diferentes regimes luminosos, para determinar os limiares térmicos inferior e superior e a temperatura ótima para a germinação. As temperaturas avaliadas foram 0; 5; 10; 15; 20; 25; 30; 35 e 40 °C, com tempos de exposição de 3, 6, 9 e 12 horas. Após cada tempo de exposição, determinou-se o número de conídios germinados e o comprimento do tubo germinativo. O delineamento experimental foi inteiramente casualizado, com quatro repetições, e os dados obtidos foram submetidos à análise de variância. Para os conídios de E. turcicum, submetidos à luz contínua, verificou-se que a maior taxa de germinação ocorreu na temperatura de 23,3 °C, para o tempo de exposição de três horas; na de 22,3 °C, para seis horas; na de 21,8 °C, para nove horas e, na de 21,7 °C, para 12 horas. Para o escuro contínuo, a maior taxa de germinação foi verificada na temperatura de 24,0 °C, para o tempo de exposição de três horas, na de 22,5 °C, para seis horas; na de 21,8 °C para nove horas e, na de 21,7 °C, para 12 horas. Os esporos de E. turcicum germinaram numa faixa de temperatura de 0 a 40 °C, sendo a temperatura ótima de 23 °C. O escuro favoreceu a germinação dos esporos de E. turcicum.

ABSTRACT Corn (Zea mays L.) is cultivated throughout Brazil and presents great economic importance. Among the diseases that cause reduction in its productivity is helmintosporiosis. The objective of this study was to evaluate the conidial germination of the pathogen that causes helmintosporiosis, Exserohilum turcicum, in different temperatures and under different light regimes, to determine lower and upper temperature thresholds and optimum temperature for germination. The temperatures evaluated were 0, 5, 10, 15, 20, 25, 30, 35, and 40 °C, with exposure times of 3, 6, 9, and 12 h. After each exposure time, the number of germinated conidia and germinative tube length were determined. The experimental design was completely randomized with four replications and the data were subjected to analysis of variance and regression. For conidia of E. turcicum subjected to continuous light, it was found that most conidia germination occurred at the temperature of 23.3 °C for 3-h exposure; at 22.3 °C for 6 h; at 21.8 °C for 9 h; and at 21.7 °C for 12 h. For continuous darkness, the higher germination was observed in the temperature 24.0 °C for an exposure time of 3 h; at 22.5 °C for 6 h, at 21.8 °C for 9 h; in 21 7 °C for 12 h. Exserohilum turcicum spores germinated in a temperature range of 0 to 40 °C, the optimum temperature being 23 °C. The dark regime favored the germination of E. turcicum spores.

RESUMO O objetivo deste estudo foi avaliar a influência de dois diferentes manejos (convencional e plantio direto) e diferentes rotações com soja e milho sobre a ocorrência de espécies de Fusarium. O trabalho foi conduzido no campo experimental e laboratório de Sementes da Iowa State University. Os tratamentos foram: manejo (plantio direto e convencional), cultura (milho e soja) e três rotações diferentes para milho e soja, respectivamente. Tratamento com milho: (1) o primeiro ano milho após quatro anos de soja (1C); (2), alternando a cada ano com a soja e milho (C / SB); (3) contínuo de milho (C). Tratamento com soja; (1) o primeiro ano de soja após quatro anos de milho (1S); (2) a soja alternada anualmente com milho (SB / C); (3) contínuo de soja (S). Duas contagens da população de plantas foram realizadas em duas épocas em soja (VC e V3) e em milho (V1 e V3). O sistema radicular de dez plantas foi coletado nos estágios vegetativo V2 para soja e V5 para milho. Os fungos foram isolados a partir das raízes, as espécies identificadas com base nas características morfológicas mais distintivas. O delineamento experimental foi em blocos casualizados com quatro repetições. Nove espécies foram identificadas tanto na soja como no milho, incluindo F. acuminatum, F. equiseti, F. graminearum, F. oxysporum, F. proliferatum, F. solani, F. subglutinans, F. verticillioides e F. virguliforme. Não houve diferenças significativas entre os tratamentos relativos à composição de espécies de Fusarium, tanto para soja quanto para milho. Foi observado que a espécies de F. oxysporum foi mais frequente seguida por F. solani para a soja. Para o milho, as principais tendências dos dados foi à predominância de F. solani em todos os tratamentos e maior frequência foi no sistema de plantio direto.

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 V3). The root system of ten plants were collected in the vegetative stages V2 and V5 for soybeans and corn. The fungi were isolated from the roots, and the Fusarium species were identified based on the most distinctive morphological characteristics. Nine species were identified in both soybeans and corn, namely F. acuminatum, F. equiseti, F. graminearum, F. oxysporum, F. proliferatum, F. solani, F. subglutinans, F. verticillioides and F. virguliforme. There were no significant differences among the treatments concerning the Fusarium species composition, for both soybeans and corn. In soybeans Fusarium oxysporum was the most frequently observed saprophyte species, followed by F. solani. For corn the main trends in the data was the predominance in all treatments of F. solani, whose highest frequency was in the no-tillage system.

Este trabalho teve como objetivo determinar a concentração ótima de conídios de F. graminearumpara inoculação artificial em espiguetas de trigo e verificar o tipo de resistência à giberela (Tipo I e/ou II) dos cultivares de trigo. O trabalho foi composto por dois experimentos, sendo que no primeiro determinou-se a concentração ótima de conídios mL-1 para inoculação artificial em quatro cultivares. Para isso, testou-se as concentraçóes de 5x103, 15x103, 25x103, 35x103 e 40x103 conídios mL-1. Vinte e um dias após a inoculação quantificou-se a incidência de F. graminearum em espiguetas, sendo que através de análise de regressão, determinou-se a concentração ótima de conídios mL-1 para cada cultivar. No segundo experimento, avaliou-se a resistência à giberela dos cultivares de trigo mediante inoculação artificial, utilizou-se a mesma metodologia do experimento anterior e a concentração de 31x103conídios mL-1. As variáveis avaliadas foram severidade, grão giberelados e incidência em espiguetas gibereladas. A melhor concentração para inoculação artificial de giberela em espiguetas de trigo é de 31x103conídios mL-1. A maior severidade da doença foi verificada para os cultivares de trigo BRS 208 e Pampeano e a maior percentagem de grão giberelado foi para o cultivar BRS 208. Os cultivares Pampeano e BRS 177 não apresentaram resistência do Tipo I à giberela, porém apresentam do Tipo II, enquanto que os cultivares Mirante e BRS 208 não apresentam nenhum dos dois tipos de resistência.

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.

A mancha-amarela do trigo, causada pelo fungo Drechslera tritici-repentis, é de ocorrência mundial e uma das principais doenças da cultura. No Brasil, a mesma está presente em todas as safras e pode reduzir o rendimento de grãos em mais de 40%. A sua ampla adaptabilidade a ambientes diversos pode estar relacionada à capacidade dos esporos germinarem sob diferentes temperaturas, assunto que foi examinado neste experimento conduzido na UPF, em 2011. Suspensões de conídios (350 µL) foram depositadas em placas de Petri com meio ágar-água e incubadas em câmara tipo BOD, na presença e ausência de luz, a -5, 0, 5, 10, 15, 20, 25, 30, 35 e 40ºC, por 2, 4, 6, 8 e 10 horas. O trabalho foi conduzido duas vezes, em delineamento inteiramente casualizado, com quatro repetições. Os conídios germinaram tanto na presença como na ausência de luz. A germinação foi nula a -5ºC ou 40ºC. A mesma foi detectada após 2h e aumentou com o tempo de incubação. Através de polinômios de segundo grau estimou-se a máxima germinação a 19ºC e 9,5h de incubação. Houve predominância da germinação bipolar (frequência de 45,0%), seguida da intercalar (33,5%) e da unipolar (21,5%). Os resultados obtidos indicam grande amplitude térmica para germinação dos conídios de D. tritici-repentis, o que explica, parcialmente, sua ampla distribuição geográfica.

Tan spot, caused by the fungus Drechslera tritici-repentis, is of worldwide occurrence and one of them main diseases affecting the wheat culture. In Brazil, tan spot is present in every crop season and may reduce grain yield by more than 40%. The great adaptability of this disease to diverse environments may be related to the capability of spores to germinate at different temperatures, which was examined in this experiment conducted at UPF, in 2011. Conidial suspensions (350 µL) were placed onto Petri plates containing water-agar medium and incubated in a BOD-type chamber, in the presence and absence of light, at -5, 0, 5, 10, 15, 20, 25, 30, 35 and 40ºC, during 2, 4, 6, 8 and 10 hours. The experiment was conducted twice, in a completely randomized design, with four replicates. Conidia germinated either in the presence or in the absence of light. Germination was null at -5ºC or 40ºC. It was detected after 2h and increased with the incubation time. Second-degree polynomials were used to estimate maximum germination at 19ºC and 9.5h of incubation. There was predominance of bipolar germination (frequency of 45.0%), followed by intercalar (33.5%) and unipolar (21.5%) germination. The obtained results showed a large temperature range for D. tritici-repentis conidial germination, which may partially explain the widespread distribution of this fungus.

Este trabalho teve como objetivo avaliar a patogenicidade e a agressividade de três raças de Cercospora sojina, em dois cultivares de soja, BMX Magna e Bragg. Para isso, preparou-se suspensão, na concentração de 40 x 10³ conídio mL-1, para inoculação das plantas. Quinze dias após a inoculação com o fungo, verificou-se que a severidade e o número de lesões por folíolo, para a raça 23, não apresentaram diferenças estatísticas entre os cultivares. Para as raças 24 e 25, o cultivar BMX Magna apresentou maior valor do grau de infecção, diferindo estatisticamente daquele do cultivar Bragg. Com relação ao diâmetro das lesões, para a raça 23, o cultivar Bragg apresentou maior valor, para a raça 24, o maior valor ocorreu em BMX Magna e para a raça 25, não houve diferença estatística entre os cultivares. Portanto, as raças de C. sojina são patogênicas para os dois cultivares de soja e há diferença de agressividade entre elas, sendo as raças 24 e 25 mais agressivas do que a raça 23.

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 10³ 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.

O objetivo desse trabalho foi avaliar a germinação de conídios horas, verificou-se que a maior germinação ocorreu na temperatura de Cercospora sojina em diferentes temperaturas com luz contínua de 23,8 ºC, para 6 horas foi de 24,3 ºC, para 9 horas foi de 22,9 ºC e no escuro, visando a determinar os limiares térmicos inferior e e para 12 horas foi de 22,4ºC. Quando as placas foram incubadas superior e a temperatura ótima. Os conídios foram depositados na no escuro, verificou-se que a maior germinação dos conídios para superfície das placas de petri contendo substrato ágar-água. Em o tempo de exposição de 3 horas foi na temperatura de 23,8 ºC, seguida foram incubadas em DBO com luz contínua e no escuro para 6 horas foi de 23,4 ºC, para 9 horas foi de 22,9 ºC e para 12 nas temperaturas (0; 5; 10; 15; 20; 25; 30; 35 e 40 ºC) e retiradas horas 22,7 ºC. A temperatura ótima para a germinação de conídios nos tempos de exposição (3, 6, 9 e 12 horas). Para os conídios de na luz contínua foi de 22,4 ºC e no escuro de 23 ºC, sendo o limiar C. sojina submetidos à luz contínua no tempo de exposição de 3 térmico inferior de 0 ºC e o superior de 40 ºC.

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.