ABSTRACT Sclerotinia sclerotiorum, a fungus that causes white-mold, is an important hard-to-control phytopathogen of several commercially valuable crops. It is necessary to search for sustainable tools for the management of this pathogen with the objective of achieving sustainability in the field. So, the research objective was to prospect bacteria for the biocontrol of this disease. A strain of S. sclerotiorum (VPB015) was used as phytopathogen. In total, 26 soil bacterial strains obtained from different collections were used, and 23 strains showed antagonistic action against fungus; of these, six produced thermostable metabolites with inhibitory action against the pathogen. Production of volatile compounds by the bacteria was not observed. The GN01 strain, identified as B. velezensis, decreased the disease severity in common-bean seedlings in soil infested with S. sclerotiorum. Five strains decreased disease severity in detached leaves. B. velezensis GN01 showed potential in disease control by seed treatment.
ABSTRACT Maize is prominent in silage production; however, the cropping season may compromise its yield performance. Nevertheless, nitrogen fertilization via irrigation has the potential to ensure high yield. The objective was to evaluate the levels of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) in the diagnostic leaf and their exports in maize for silage cultivated under increasing doses of N via fertigation, in Canindé de São Francisco, Sergipe, Brazil. The experiment was conducted in summer (January to April) and winter (June to September) of 2016. The experimental design was a randomized complete block design, with four replications and four N doses (0, 80, 160, and 240 kg ha⁻1), with a combined analysis of the growing seasons. Nutrient contents in the diagnostic leaf were increased with increasing N doses, except for Ca. Maize cultivated in winter showed higher contents of N (28.65 g kg⁻1) and P (3.59 g kg⁻1), while in summer the plants showed higher values for K (25.2 g kg⁻1), Ca (4.60 g kg⁻1), and Mg (8.52 g kg⁻1). The decreasing order of nutrient export was: N > K > Mg > Ca > P. In summer, exports of P (64.34 kg ha⁻1), K (156.99 kg ha⁻1), and Mg (78.35 kg ha⁻1) were favored up to the N dose of 124.43 kg ha⁻1. In the winter season, there were higher exports of N (185.01 kg ha⁻1), Mg (78.83 kg ha⁻1), and Ca (74.43 kg ha⁻1), especially with the application of 240 kg ha⁻1 of N.
ABSTRACT Soil mineralogy is a major determinant of soil physical, chemical, and biological properties. In semiarid environments, pronounced mineralogical heterogeneity requires specific management practices. This study characterized the mineralogy of the clay fraction of soils from rural communities in Mossoró, Rio Grande do Norte, Brazil, and evaluated the influence of parent material on mineralogical composition and pedogenetic development. Eight soil profiles were selected from 15 previously described profiles, and mineralogical analyses were performed on their diagnostic horizons. Iron forms were quantified by sulfuric acid digestion to determine iron associated with secondary minerals (Fes), dithionite-citrate-bicarbonate extraction to quantify free crystalline iron (Fed), and acid ammonium oxalate extraction to estimate low-crystallinity iron (Feo). The qualitative mineralogy of the clay fraction was determined by X-ray diffraction (XRD) using oriented slides subjected to the different chemical and thermal treatments. The soils were classified predominantly as mesoferric and hypoferric. XRD indicated the predominance of kaolinite, 2:1 phyllosilicates, probably illite and/or smectite, and iron oxides, with limited variation among parent materials. Under semiarid conditions, weathering and pedogenetic evolution, expressed by the mineral assemblage of the clay fraction and by iron forms, directly depended on parent material. These characteristics influence nutrient dynamics, natural soil fertility, and agricultural management in semiarid regions.
ABSTRACT Semen cryopreservation is essential for the conservation and maintenance of germplasm stocks from several species, each of which has specific requirements for successful cryopreservation. The objective of this study was to develop a sperm preservation protocol for Prochilodus lineatus (curimba) using the sugars trehalose, sucrose, lactose, and raffinose. Because synergy among cryoprotectants is not always beneficial, each cryoprotectant was tested separately at three concentrations (50, 100, and 150 mM), and dimethyl sulfoxide (DMSO) was used as the control. After thawing, sperm kinetic parameters were analyzed using computer-assisted sperm analysis (CASA), and cellular functional parameters were assessed by flow cytometry. In the sperm kinetic analyses, only the amplitude of lateral head displacement did not differ statistically from the control (p > 0.05), whereas the other parameters were lower than those of the control. In the motility-period analysis, 100 mM trehalose was superior to the control (p < 0.05), supporting its use in the protocol. However, the results for the different parameters analyzed showed that the other sugars tested were not superior to the control (10% DMSO), indicating that they were not effective for cryopreservation. Trehalose at 100 mM showed the most favorable response among the tested sugars for P. lineatus sperm cryopreservation.
ABSTRACT Among the environmental factors influencing plant development, light is one of the most critical, directly affecting growth and physiological processes. Fluctuations in light intensity can significantly alter plant physiological mechanisms. This study aimed to evaluate the effects of different photosynthetically active radiation flux densities (PPFD) on the physiological responses of desert rose throughout the day. The experimental design was completely randomized, with treatments consisting of 18 photosynthetic photon flux densities (0, 25, 50, 75, 100, 125, 150, 175, 200, 400, 600, 800, 1,000, 1,200, 1,400, 1,600, 1,800, and 2,000 μmol m⁻2 s⁻1) and three evaluations throughout the day (8 a.m., 12 p.m., and 4 p.m.). Variations in gas exchange were analyzed, as were the flux densities that promote greater chlorophyll fluorescence and electron transport rate in desert rose plants. The results showed that physiological processes varied significantly with PPFD throughout the day. At 12 p.m., a PPFD between 1800 and 2000 μmol m⁻2 s⁻1 favored the highest rates of CO₂ assimilation, stomatal conductance and transpiration. Chlorophyll fluorescence, especially maximum and variable, was also increased under high irradiance, while initial fluorescence was higher under low light availability. The results highlighted the influence of photon flux on photosynthetic efficiency, gas exchange and fluorescence parameters, demonstrating the importance of times of the day in CO₂ assimilation and stomatal opening.
