Idalmir dos Santos

Escala diagramática para avaliação de severidade da helmintosporiose comum em milho

The Helminthosporium leaf blight, caused by Exserohilum turcicum, is one of the main spots that attacks corn crop in Southern Brazil. This disease causes considerable economic losses on this crop, especially when the attack begins before the flowering period. The aim of this research was to elaborate and validate a diagrammatic scale to evaluate the severity of the Helminthosporium leaf blight in corn. Corn leaves with symptoms of the disease were collected for measuring the real severity and defining the maximum and minimum limits, as well as the intermediate levels and the logarithmic increments, according to Weber-Fechners stimulus-response law. The elaborated scale suggested seven severity levels: 0,5; 1,0; 2,5; 6,5; 15,5; 30,0 and 54,0%. The validation was performed by six persons without previous experience to quantify this disease. The severity of 30 leaves with different levels of symptoms was estimated, with and without the help of the scale. The use of the diagrammatic scale resulted in better accuracy and precision in the estimates, being a tool for quick and easy use, which can be adopted to assist in the severity evaluation of the Helminthosporium leaf blight in corn.

Reação de genótipos de feijão ao crestamento bacteriano comum, avaliado por dois métodos de inoculação

The knowledge of resistance of bean genotypes to pathogens is important to genetic breeding programs. Two methods of bacterial inoculation were tested to evaluate the sensitivity of bean genotypes to common bacterial blight, caused by Xanthomonas axonopodis pv. phaseoli. Leaves of 56 bean genotypes were inoculated by the method of multiple needles and the method of incision with scissors, using the isolated XAP 15497. We classified 21 genotypes as resistant, 13 as moderately resistant, 9 as moderately susceptible, and 13 as susceptible by the method of inoculation with multiple needles. With the method of inoculation with scissors it was possible to classify 24 genotypes as resistant, 21 as moderately resistant, 7 as moderately susceptible, and 4 as susceptible. The genotypes IPR Chopim, IAPAR 81, IAPAR 16, BRS Campeiro, BRS Radiante, IAPAR 80, UTF 6, SM 9906, PI 2072620, LP 01-51, PB 4, Uirapuru, IAPAR 20, Zonin, IAPAR 31, 2 V, CNPF 7762, BRS Talisma, Perola, Lon Rosinha, and UTF 9 had similar behavior in the two methods of inoculation. Both methods of inoculation were efficient in determining the reactions of susceptibility and resistance of the genotypes but the method of inoculation with multiple needles was more precise and practical in the evaluation of the inoculated portion of the leaf.

Influência da nutrição mineral foliar sobre doenças da parte aérea da cultura do trigo

The use of fungicide for controlling of wheat foliar diseases is a common practice among farmers. However, due to the environmental impact caused by widespread use, some alternative pathogen controls are needed. This work aimed to evaluate the effect of leaf mineral nutrition on the control of wheat foliar diseases, and its effect on the plant. The experiment was arranged in a randomized block design with four replications and four treatments: 1- control; 2- leaf fertilization at 30 days after emergence (DAE) and at 75 DAE; 3- fungicide at 30 and 75 DAE; and 4- leaf fertilization at 30 DAE and foliar fertilizing + fungicide at 75 DAE. Nine incidence evaluations were carried out for powdery mildew to calculate the area under the disease progress curve; three evaluations for rust severity and gluma spots; and two evaluations for yellow spot yield, mass of fresh and dry matter of aerial parts and root system were determined. There was reduction in the intensity of powdery mildew as a function of leaf fertilization, only in the first evaluation of incidence and in the second and fifth evaluations of severity. There was complementary effect of the nutrients with the fungicide for reducing diseases only for yellow spot, with a reduction in severity of approximately 11.16 %. Higher yield was recorded for the treatments with fungicide only and for fungicide + nutrients. Leaf fertilization promoted increase in root fresh mass and root dry mass; however, there was no increase in fresh mass of aerial part as a function of the leaf fertilization.

Efeito do chorume líquido de suínos na podridão do colo e tombamento de plântulas de feijoeiro causadas por Sclerotium rolfsii

Liquid swine manure (LSM) can be used as a source of nutrients and organic matter for some agricultural crops, and may interfere in plant diseases caused by soil-borne plant pathogens. Thus, the effect of LSM on bean (Phaseolus vulgaris) diseases caused by Sclerotium rolfsii was studied. LSM was incorporated into 1 m2 plots at doses equivalent to 0, 20, 40, 60, and 80 m3 ha-1. The soil was infested two months prior to LSM application with 100 g of substrate (unhulled rice) colonized by the pathogen. Eighty bean seeds were sown per plot in two successive cultivations, 1 day and 45 days after LSM application. Intensity of the disease was evaluated based on plant emergence, final stand, and severity of the disease, in both cultivations. Microbial activity, ammonia concentration at the soil surface layer, and fertility levels were only evaluated in the second cultivation. A reduction in disease intensity was observed as LSM doses increased. Among the characteristics evaluated, the factors that best explain such a reduction are increased microbial activity, ammonia concentration, and copper and zinc levels.

Potencial de extratos à base de Calendula officinalis L. na indução da síntese de fitoalexinas e no efeito fungistático sobre Botrytis cinerea, in vitro

Three experiments were carried out to evaluate the potential of calendula (Calendula officinalis L.) extracts for phytoalexin induction in soybean cotyledons, resistance mechanism induction in strawberry fruits and fungistatic effect on Botrytis cinerea in vitro. Experimental design was completely randomized with 15 treatments resulting from the combination of three forms of extraction (alcohol extract, infusion and maceration) at five concentrations (zero, 1.25, 2.5, 5 and 10%). Results showed that C. officinalis extracts could induce the phytoalexins glyceollins in soybean cotyledons. In the application of extracts during the strawberry postharvest, there was a change in flavonoid content, as well as in the activity of the enzyme PAL, which was stimulated by the application of extracts; however, fruit rot control was not noted. Fungistatic effect was observed for the extract obtained by maceration at all used concentrations, reducing in vitro the growth of the fungus B. cinerea, and from 2.5% there was total inhibition. The extract obtained by infusion also showed a positive response in reducing B. cinerea growth, with better response at the concentration of 10% extract.

PLANO AMOSTRAL PARA A AVALIAÇÃO DA SEVERIDADE DE PODRIDÃO-PARDA EM PÊSSEGOS SUBMETIDOS A DIFERENTES EXTRATOS VEGETAIS

The identification of brown rot control derivatives has been the focus of intense research owing to the negative effects of the unrelenting usage of fungicides. Brown rot, caused by Monilinia fructicola, is an important post-harvest disease of peaches. The goal of this study was to estimate the optimum sample size of peaches in order to assess the average lesion size and the influence of different plant extracts on the fruits. Three preparation forms (FPE) were evaluated, as well as another seven forms of application (FAE) of canola and mustard extracts on peaches, with applications of the pathogen’s inoculum. Five fruits were utilized in five repetitions per treatment. Evaluation involved measurement of the fruits’ lesioned areas. The necessary sampling size was determined for estimation of the averages for each treatment and experiment. For measurement of the lesion size, 99 fruits in FPE and 23 fruits in FAE were sufficient for estimating the average with an estimation error of 10%. Based on the same estimation error, the sampling size is contingent on the extracts (canola, and mustard), batches of fruits, forms of extraction, and extract application on the fruits.

Propolis for the control of powdery mildew and the induction of phytoalexins in cucumber

espanolDebido a sus propiedades antimicrobianas el propoleo ha sido utilizado por el hombre desde hace milenios, sin embargo solo recientemente se ha probado como un agente antimicrobiano agricola. Ademas, la capacidad de este producto para activar los mecanismos de defensa de la planta es muy prometedor, debido a la gran cantidad de sustancias en su composicion. Por tanto, el objetivo de este estudio fue evaluar el efecto de diferentes concentraciones y tiempos de aplicacion de los extractos etanolicos de propoleos (EEP) en el oidio (Podosphaera fuliginea) en cultivos de pepino, para establecer el metodo mas adecuado para el control y la existencia o no de este potencial para inducir los mecanismos de defensa de la planta. El experimento se llevo a cabo en macetas en un invernadero. Fue empleado un diseno experimental completamente al azar, utilizando un factorial 6x3, que consiste en seis concentraciones (0; 0,5; 1; 2; 4 y 8%) y tres momentos de aplicacion EEP (24 horas antes de la inoculacion del patogeno, 24 horas despues de la inoculacion de patogenos y en la aparicion de los primeros sintomas de la enfermedad) con cuatro repeticiones. Las evaluaciones para la incidencia y gravedad de la enfermedad se realizaron semanalmente. El experimento se repite para mas de un cultivo, siguiendo la misma metodologia establecida en la primera. Tambien se evaluo el efecto de diferentes concentraciones de EEP en la activacion de los mecanismos de defensa de la planta, mediante la induccion de fitoalexinas en la soja (Glycine max), cotiledones. Se observo una interaccion significativa entre los factores de concentracion (x tiempo de aplicacion) para la incidencia de la enfermedad. Para el area bajo la curva de progreso de la enfermedad (AUDPC) para la gravedad no hubo interaccion observada entre los factores, sin embargo, se observaron diferencias significativas para los dos factores por separado. El AUDPC para la incidencia fue menor para la aplicacion 24 horas despues de la inoculacion de patogenos a la mayor concentracion. El EEP inducida aumento los niveles de fitoalexina en cotiledones de frijol de soya segun la concentracion aplicada. Los extractos etanolicos de propoleos podrian tener potencial para el control del mildiu pulverulento, principalmente en los pepinos, por medio de la aplicacion preventiva de una concentracion al 8%. EnglishDue to its antimicrobial properties propolis has been utilised by man for millennia, however, only recently has its use as an agricultural antimicrobial agent been tested. The capacity of this product to activate plant defence mechanisms is highly promising, due to the large number of substances in its composition. Therefore, the objective of this study was to evaluate the effect of different concentrations and application times of ethanol extracts of propolis (EEP) on powdery mildew (Podosphaera fuliginea) in cucumber crops, to establish the most suitable method for control and whether or not there is potential to induce plant defence mechanisms. The experiment was conducted in pots in a greenhouse. A completely randomised experimental design was employed, using a 6x3 factorial consisting of six concentrations (0; 0.5; 1; 2; 4 and 8%) and three EEP application times (24 hours before pathogen inoculation, 24 hours after pathogen inoculation and at the onset of first symptoms of the disease), replicated four times. Evaluations for disease incidence and severity were made weekly. The experiment was repeated for a second crop, following the same methodology established in the first. We also evaluated the effect of different EEP concentrations on the activation of plant defence mechanisms, through the induction of phytoalexins in soybean (Glycine max) cotyledons. A significant interaction was observed between the factors (application time x concentration) for disease incidence. For the area under the disease progress curve (AUDPC) for severity there was no interaction observed between the factors, however, we observed significant differences for the two factors separately. The AUDPC for incidence was less for the application 24 hours after pathogen inoculation, principally at the highest concentration. The 8% concentration of EEP controlled disease severity by 31.33 and 43.68% for the first and second crops, respectively. The application of the concentrations 24 hours before and 24 hours after pathogen inoculation showed less AUDPC for severity, but this difference was not significant for either crop. The EEP induced increasing phytoalexin levels in soybean cotyledons as the applied EEP concentration increased. Ethanol extracts of propolis could have potential for the control of powdery mildew, principally in cucumbers, through the preventive application of an 8% concentration.