Scielo RSS <![CDATA[Bragantia]]> vol. 76 num. 3 lang. en <![CDATA[SciELO Logo]]> <![CDATA[Involvement of peroxidases in structural changes of barley stem]]> ABSTRACT The aim of this study was to investigate anatomical characteristics of barley (Hordeum vulgare L.) internodes and to reveal the connection with activity of guaiacol-peroxidases, their isoenzyme profiles, lignin, and cellulose content. Three lower internodes were sampled at elongation stage and differed in their anatomical features by showing that lignin deposition follows developmental pattern. Epidermis and hypodermis in the first internode were characterized by continuous layer of the lignified cells while in the second and third internode thin walled parenchyma cells could be observed in the hypodermis. These observations were in accordance with increment of peroxidase activity from the first to the third internode. Two acidic and 2 basic isoforms of peroxidases were present. The third internode had higher total soluble protein content and lower dry weight as well as Klason lignin content in comparison to the first and second internode. Studying lignification process in barley stem by using anatomical and physiological approach will provide valuable information regarding developmental changes connected with lignin deposition in the stem. <![CDATA[Prohexadione calcium reduces vegetative growth and increases fruit set of ‘Smith’ pear trees, in Southern Brazil]]> ABSTRACT Prohexadione calcium (P-Ca) has been reported to effectively control shoot growth in several pear cultivars, but with a few reports about its efficiency under the climatic conditions of southern Brazil. Therefore, the objective of this study was to evaluate vegetative growth, production, and fruit quality of ‘Smith’ pear trees in response to the use of different rates of P-Ca in the climatic conditions of southern Brazil. The experiment was conducted during the 2013/2014 and 2014/2015 seasons, in a 6-year-old ‘Smith’ pear orchard, trained to a central-leader system, with spacing of 1.5 × 4.8 m, grafted onto Pyrus calleryana Decne. Different P-Ca rates were applied (100, 200, 300, and 400 mg∙L–1) in different stages: first, in early spring for all treatments, and the others when shoot growth resumed (GR), but only for some treatments. Variables for vegetative growth, yield components and fruit quality at harvest and post-harvest were evaluated. The use of P-Ca was effective to control vegetative growth in both seasons, at different rates. Yield components were not affected by P-Ca applications in 2013/2014, except return bloom and return yield. In 2014/2015 season, P-Ca applications positively affected yield components, except average fruit weight and return bloom. P-Ca applications did not alter the qualitative attributes of the fruits of ‘Smith’ pear trees at harvest and after a period of cold storage. These results implicate P-Ca as a potential tool to manage vigor of ‘Smith’ pear trees in climatic conditions of southern Brazil. <![CDATA[Development of mango wilt in mango cultivars submitted to salt stress]]> ABSTRACT Mango wilt, caused by Ceratocystis fimbriata, is one of the most important diseases affecting mango yield worldwide. Salt stress can affect host defense responses against pathogens infection. The aim of this study was to evaluate the development of mango wilt in 2 mango cultivars submitted to salt stress. Mango plants from cultivars Tommy Atkins and Ubá, considered to be moderately resistant and resistant to mango wilt, respectively, were grown in plastic pots which contained 20 kg of washed sand and daily irrigated with 3 L of a modified Hoagland solution during 40 days before being submitted to salinization. For this process of salinization, the plants received nutrient solution containing 0, 30, 60, and 90 mmol∙L–1 of sodium chloride (NaCl) during 50 days. At the 50th day, the plants were inoculated with C. fimbriata, and disease development was evaluated at 42 days after inoculation. During this period, the plants were also submitted to salinization. After disease evaluation, the stems of plants from each treatment were collected to determine the concentrations of chlorine (Cl) and sodium (Na). Plants from the 2 cultivars showed reduced mango wilt symptoms as the NaCl doses increased from 0 to 90 mmol∙L–1. Plants submitted to the highest NaCl doses showed greater Cl and Na concentrations on the stem. In conclusion, the resistance of plants against C. fimbriata infection can be potentiated when submitted to salt stress regardless of their basal level of resistance to mango wilt. <![CDATA[Potential of popcorn germplasm as a source of resistance to ear rot]]> ABSTRACT Because of its multi-purpose nature, popcorn has sparked the interest of the World Trade Organization as regards fungal contamination by mycotoxins. However, no investigations have been conducted on popcorn for resistance of genotypes to ear rot. The aim of this study was to evaluate the potential of popcorn genotypes as to resistance to ear rot and rotten kernels, as an initial step for the implementation of a breeding program with the popcorn crop in Northern Rio de Janeiro State, Brazil. Thirty-seven accessions from different ecogeographic regions of Latin America were evaluated in 2 cultivation periods, in a randomized block design with 4 replications. We evaluated the incidence of rotten ears, incidence of rotten ears caused by Fusarium spp., severity of ears with Fusarium spp. rot, and incidence of rotten kernels. The results were subjected to analysis of variance, and means were compared by the Scott-Knott clustering test (p &lt; 0.05). A significant effect was observed for all evaluated variables, characterizing them as efficient in the discrimination of genotypic variability for reaction to fungal injuries in popcorn. The gene pool of the tropical and temperate Germplasm Collection evaluated here has the potential to generate superior segregants and provide hybrid combinations with alleles of resistance to diseases affecting ears and stored kernels. Based on the different variables and times, the experiment was conducted, and genotypes L65, L80, and IAC 125 showed the highest levels of resistance. <![CDATA[Sampling grids for monitoring <em>Euschistus heros</em> infestation in soybean]]> ABSTRACT Euschistus heros is one the most important pest insect in soybean fields in Brazil. Therefore, site-specific management applied for controlling E. heros can result in economic and environmental benefits. However, sampling protocols for assessing spatialtemporal variability of this soybean pest and, then, for guiding a more sustainable pest management, were still unknown. Thus, the objective of this study was to compare the efficiency of sampling grid sizes for monitoring the spatial variability of E. heros infestation along the soybean reproductive stages. Nine sampling campaigns were carried out using the beating sheet method, from R2 to R7 soybean phenological stages. It was used a sampling grid of 10 × 10 m, totaling 338 points in an soybean field of 3.4 ha, located in Londrina, PR, Brazil, during the 2011/2012 growing season. Increased sampling grid sizes (i.e., 10 × 10 m, 10 × 20 m, 20 × 20 m, 20 × 30 m, 30 × 30 m, 30 × 40 m, and 40 × 40 m) were simulated by deleting points from the initial (reference) sampling grid. The data were analysed through statistical and geostatistical procedures. Thematic maps were built and compared using Pearson’s correlation and relative deviation coefficient (RDC). Spatial variability distribution pattern of E. heros infestation was dependent on sampling grid size and infestation pressure, in which smaller sampling grids and higher E. heros infestations enabled a more accurate monitoring. Based on study, an accurate protocol (r &gt; 0.70 and RDC &lt; 20%) for monitoring high infestation (i.e., &gt; 2 individual per meter) of E. heros in soybean reproductive stages should include sampling grids smaller or equal to 20 × 20 m. <![CDATA[<em>Annona crassiflora</em> Mart. (Annonaceae): effect of crude extract of seeds on larvae of soybean looper <em>Chrysodeixis includens</em> (Lepidoptera: Noctuidae)]]> ABSTRACT The effect of a crude extract of Annona crassiflora was evaluated on larvae of the soybean looper, Chrysodeixis includens (Lepidoptera: Noctuidae) in different stages of larval development. The extract was prepared with seeds of A. crassiflora fruits collected in the state of Mato Grosso, Brazil. The extract was diluted in water and solubilizer agent at the concentrations of 0.5, 1.0, 2.0, 4.0, and 8.0%; it was tested by ingestion of treated leaves and contact. The mortality rate of topically treated caterpillars of first, third, and fifth instars was significantly higher than that of the control group. For first instar caterpillars, mortality was observed within the first 24 h after application, while, for the remaining instars, it was significant after 72 h. For caterpillars fed treated leaves, no differences in mortality rates were observed within the first 120 h. These caterpillars were monitored until the end of the larval stage, during which mortality rates increased for first and third instar caterpillars. The mortality rate of fifth instar larvae was not significantly different between treatments. The treatment by ingestion was not efficient over a short period of time, but reduced the number of caterpillars that completed their development, decreasing the number of insects in the following generation. We concluded that the crude extract of A. crassiflora affected the development of C. includens and is a promising compound for the control of this pest. <![CDATA[Food quantity and quality of cassava affected by leguminous residues and inorganic nitrogen application in a soil of low natural fertility of the humid tropics]]> ABSTRACT The aim of this study was to test the hypothesis that the quality and quantity of biofortified cassava root in a humid tropical environment can be modified with the application of a combination of low- and high-quality residues of leguminous tree species. The experiment was designed as a 6 × 2 factorial (a combination of 4 legume species versus 2 levels of nitrogen) with 4 replications in a randomized block design and the following treatments: Gliricidia + Acacia, Gliricidia + Leucaena, Gliricidia + Clitoria, Leucaena + Acacia, Leucaena + Clitoria, and a control without legumes. We analyzed the shoot weight, number of roots/plant, root weight, root production, proximate composition, as well as the mineral, carotenoid, and pro-vitamin A contents. Root production increased with the application of high-quality residues. The protein level influenced the carotenoid content. The allelopathic effect of exotic genera — Leucaena and Acacia —, especially when combined, can decrease the mineral content such as potassium and, therefore, reduce the accumulation of starch. <![CDATA[Differential response of microbial respiration to supplied nitrogen forms in 3 contrasting alpine meadow soils on the Tibetan Plateau]]> ABSTRACT An incubation experiment was conducted to examine the effects of nitrogen (N) applications in different forms (NH4NO3, NH4Cl, and KNO3) on microbial respiration considering 3 different alpine meadow soils (C poor soil, pH = 8.1, 1.6% C; C moderate soil, pH = 6.0, 5.0% C; C rich soil, pH = 7.1, 7.4% C) in the Tibetan Plateau. The addition of NH4NO3 and NH4Cl increased the microbial respiration in C poor soil, but KNO3 had no effect. The inorganic N forms had no effects on C rich soil, but decreased microbial respiration in C moderate soil. Soil microbial respiration levels across the different types were ordered as follows: C poor soil &lt; C rich soil &lt; C moderate soil, regardless of N addition. These results suggest that the effect of N on microbial respiration in alpine meadow soils is more dependent on the initial soil pH than on soil C availability. <![CDATA[Phosphorus fractions in apple orchards in southern Brazil]]> ABSTRACT Phosphorus (P) applications at dosages higher than the necessary may cause P buildup in the soil labile fractions and, consequently, pollution of water sources. This study aimed to assess accumulation of P fractions as well as the parameters of adsorption isotherms in soil profiles having a history of application of phosphate fertilizers and cultivated with apple trees. Soil samples were collected from an area with no history of cultivation and 2 apple orchards cultivated for 8 (P8) and 18 (P18) years, in the city of Urubici, Santa Catarina, southern Brazil. Soil samples were air dried, sieved in a 2-mm mesh, and subjected to chemical analyses (P adsorption) besides P chemical fractionation. Applications of phosphate fertilizers to the orchards, particularly P18, increased the inorganic and organic concentrations of P in all fractions. The distribution of P in organic and inorganic forms in the planted soils was similar to the distribution observed for the native vegetation soil. The highest inorganic labile P fraction, the lowest maximum P adsorption capacity, and the highest equilibrium concentration values at P18 are indicators of a higher environmental pollution risk of the orchards soils compared to the native soil. <![CDATA[Surface and incorporated liming effects on clay dispersion, water availability, and aeration capacity of a Dystrudept soil]]> ABSTRACT Liming represents a management procedure that can affect the soil structure and its thermodynamic processes. In this context, the aims of this study were to assess (i) the effects of the surface and incorporated liming on the clay dispersion, soil water availability, and aeration capacity; (ii) the influence of soil chemical alterations in its physical attributes. For this, a field experiment was installed in a family farming property, located in the southeastern region of the State of Paraná, in a Dystrudept soil. The treatments were 3 application modes (on the surface, incorporated via plowing and incorporated via subsoiling and harrowing), with and without 15 Mg∙ha–1 of lime, aiming to increase the base saturation in the topsoil (0 – 0.20 m) to approximately 70%. Eighteen months after application, undisturbed and disturbed soil samples were collected from the 0 – 0.10 and 0.10 – 0.20 m layers to evaluate the waterdispersed clay (WDC), water content at the field capacity (θFC) and at the permanent wilting point (θPWP), plant available water capacity (PAWC), relative water capacity (RWC), aeration capacity (AC), granulometry and the soil structural and chemical attributes. WDC content in the 0 – 0.10 m layer increased when the soil was revolved and it was influenced exclusively when lime was applied on the soil surface. With surface liming there were increase in θFC, θPWP, PAWC and RWC, and reduction in AC in the 0 – 0.10 m layer. In the 0.10 – 0.20 m layer isolated effects were verified of the modes application and liming on θFC, PAWC and RWC, while θPWP was not influenced by treatments. The soil water availability and aeration capacity alterations were mainly affected by micro and macroporosity increases, pH reduction, Al3+ precipitation, and substitution of this ion in the exchange complex by Ca2+ and Mg2+. <![CDATA[TVDI spatiotemporal pattern of a soybean growing area in humid subtropical climate]]> ABSTRACT The most southern Brazilian state, Rio Grande do Sul, is characterized by high crop yield and is, currently, the third leading soybean producer in the country. Therefore, agriculture is very important to the economy of the region. Because agriculture is highly dependent on variable weather parameters, the present study aimed to test the Temperature-Vegetation Dryness Index (TVDI) as a regional indicator of water status under the climate and soybean crop management conditions that predominate in northwestern Rio Grande do Sul. For this, soybean crop seasons with contrasting yields were selected: 2004 – 2005 (yield 0.5 t∙ha–1) and 2009 – 2010 (2.7 t∙ha–1). TVDI was obtained from the surface temperature (TS) and Normalized Difference Vegetation Index (NDVI) images available from MODIS products, which were correlated to obtain a triangular scatter plot. Rainfall data from surface weather stations were also used. The results showed that the pattern of the TVDI is associated with rainfall variability. However, as the TVDI is based on normalization of the wet and dry edges of each image individually, the comparison of TVDI values across different images is challenging. This deficiency can be mitigated by analysis of the parameters used to derive the index. Therefore, both the TVDI and the “b” and TSmin parameters used to derive it can elucidate the patterns of crop response to water availability.