V6 Stage Research Articles

MISIRoot: A Robotic, Minimally Invasive, in Situ Imaging System for Plant Root Phenotyping

HighlightsA non-destructive, in situ, and low-cost root phenotyping system was developed.The system can collect color images and 3D cloud points of corn roots in soil.When tested in a greenhouse, the scanning process did not cause significant disturbance of corn plants.The results showed significant differences in root growth for different watering treatments and growth stages.Abstract. Plant root phenotyping technologies play an important role in breeding, plant protection, and other plant science research projects. Root phenotyping researchers urgently need technologies that are low-cost, in situ, non-destructive to roots, and suitable for the natural soil environment. Many recently developed root phenotyping methods, such as minirhizotron, X-CT, and MRI scanners, have unique advantages in observing plant roots, but they also have disadvantages and cannot meet all the critical requirements simultaneously. This study focused on the development of a new plant root phenotyping robot, called MISIRoot, that is minimally invasive and works in situ in natural soil. The MISIRoot system mainly consists of an industrial-level robotic arm, a miniature camera with lighting, a plant pot holding platform, and image processing software for root recognition and feature extraction. MISIRoot can acquire high-resolution color images of roots in soil with minimal disturbance to the roots and measure the roots’ three-dimensional (3D) structure with an accuracy of 0.1 mm. In tests, well-watered and drought-stressed groups of corn plants were measured with MISIRoot at the V3, V4, and V5 growth stages. The system successfully acquired RGB color images of the roots and 3D point cloud data containing the locations of the detected roots. The plants measured with MISIRoot and the plants not measured (control) were carefully compared with the results from a hyperspectral imaging facility (reference). No significant differences were found between the two groups of plants at different growth stages. Keywords: 3D point cloud, Low-cost phenotyping, Minimally invasive root measurement, Plant root phenotyping, Robotic arm application, Root imaging.

Biological control of Meloidogyne javanica in bean plants by Hohenbuehelia spp. and Trichoderma koningiopsis

ABSTRACT Nematode control strategies are limited and alternative control is demanded. The main aim was to evaluate control potential of Hohenbuehelia spp. (Hohenbuehelia mastrucata, Hohenbuehelia barbatula, Hohenbuehelia bullulifera, Hohenbuehelia portegna, Hohenbuehelia petaloides and Hohenbuehelia paraguayensis) and Trichoderma koningiopsis against Meloidogyne javanica in bean plants in greenhouse. The parameters evaluated were the number of galls and egg masses which were evaluated in three root regions: basal, intermediate and tip; nematode reproduction factor; vegetal growth parameters (plants height on V1, V2, V4, and R5 growth stages, root length, dry weight of root and aerial part dry weight); Treatments were composed by individual interactions of each fungal isolate with 4,000 eggs of M. javanica, having a total control (bean) and a partial control (bean + nematode) arranged in completely randomized design with four repetitions. Data were tested by Scott–Knott (5%). For vegetal growth parameters, there was only significance for dry weight of roots. All species were able to control nematodes.

NITROGEN ACCUMULATION AND EXPORT BY COMMON BEAN AS A FUNCTION OF STRAW AND N SPLITTING IN NO-TILLAGE SYSTEM

ABSTRACT Determining nitrogen (N) accumulation and export by common bean as a function of straw and of the splitting of this nutrient is very important, aiming at the management and sustainability of agricultural systems. This study aimed to determine the N accumulation and export by common bean as a function of Zea mays and Urochloa ruziziensis grass straw (maize, maize/U. ruziziensis intercropping and U. ruziziensis) and splitting of top-dressing N fertilization. The experiment was conducted in Jaboticabal-SP-Brazil, during the 2012/13 crop season, in a Red Eutrophic Oxisol (Eutrudox) in no-tillage under irrigation. The experimental design was a randomized block with split plots with four replicates, totaling 120 subplots sized in 25m2 each. The plots consisted of the cropping systems prior to common bean: maize, maize/ U. ruziziensis intercropping and U. ruziziensis. The subplots were composed of ten top-dressing N fertilization splitting schemes (NS) at the phenological stages V3, V4 and R5 in different combinations. Common bean grain yield differs among cropping systems and as a function of top-dressed N split application. U. ruziziensis grass as single crop promotes greater N accumulation in common bean shoots compared to maize and its intercropping with U. ruziziensis grass. Regardless the cropping system, top-dressing N application in a single dose (90 kg ha-1) at V4 leads to similar accumulations and exports to those found in the absence of N fertilization. Splitting schemes with N application at the R5 stage increase the exports of this nutrient by common bean in succession to maize and its intercropping with U. ruziziensis grass.

Does crop succession and nitrogen splitting fertilization change the technological quality of common bean?

ABSTRACT The crop succession and nitrogen splitting fertilization are managements that can affect the common bean technological quality and, consequently, the profitability of producer and the food biological value. The aim of this study was to evaluate whether crop succession and N splitting fertilization promote differences in the technological quality of common bean grains. The experiment was carried out during winter over two agricultural years in southeastern Brazil. A randomized block design was used in a split-plot scheme, with four replications. The plots were composed of three crop successional systems (maize sole, maize + Urochloa ruziziensis, U. ruziziensis sole) and the subplots contained nine combinations of N splitting fertilization at a rate of 90 kg·ha-1 N top-dressing in the phenological stages V3, V4, and R5 of the common bean and a control without fertilization. The evaluated variables were: sieve yield greater than or equal to 12 (SY ? 12), crude protein content, cooking time, and hydration ratio. Crop succession promotes differences in the technological quality of common bean; however, the N splitting fertilization did not change the technological attributes of grains. The highest technological quality of common bean was obtained after succession with U. ruziziensis sole, generating large size and crude protein content of grain, followed by the succession with maize + U. ruziziensis intercropping, and finally, the succession with maize sole. Therefore, the crop succession is a fundamental factor for obtaining common bean with higher technological quality, affecting the food biological value and the profitability of producers.

Relativna osetljivost konvencionalne soje u zavisnosti od fenofaze razvoja na tri različita herbicida na bazi dikambe

Widespread use of dicamba-based herbicides such as Clarity® (dicamba diglycolamine salt, 480 g l-1), Engenia® (dicamba N,N-Bis-[3-aminopropyl] methylamine salt, 600 g l-1) and XtendiMax® (dicamba diglycolamine salt, 350 g l-1)with Vapor-Grip Technology for weed control in dicamba-tolerant (DT) crops have resulted in UN-intended drifts, partly due to windy and common temperature inversions in many parts of United States. It is unclear if the dicamba-based herbicides made of different formulations or technologies have differential impact on sensitive soybeans including a conventional variety. Thus, field studies were conducted in 2016 and 2017 to evaluate the relative sensitivity of a conventional soybean to micro-rates of three dicamba-based herbicide products (Clarity®, Engenia® and XtendiMax® ) applied at second trifoliate (V2), seventh trifoliate/beginning of flowering (V7/R1), and full flowering (R2) stages of soybean. The dicamba micro-rates were 0, 0.56, 1.12, 5.6, 11.2, and 56 g ae ha-1; equivalent to 0, 1/1000, 1/500, 1/100, 1/50, 1/10 of the standard rate (560 g ae ha-1) respectively. The experimental design was a randomized complete block design in a split-split-plot arrangement with 4 replications. There was no significant difference in visual injury, growth or yield response of the conventional soybean to the three dicamba herbicides. The dicamba micro rates caused 40-80% visual injury and 0-97% yield loss depending on the growth stage of application. The estimated effective doses (ED values) suggested that conventional soybeans exposed to dicamba micro-rates at V7/R1 growth stage were more sensitive than those exposed at V2 and R2 growth stages. Based on the ED values, about 0.1% of dicamba standard rate was enough to cause 10% soybean yield loss when applied at V7/R1 stage; while about 1% of dicamba standard rate was required to cause the same level of yield loss when applied at V2 or R2 stage. By implication, dicamba drift on sensitive soybean plants should be avoided to prevent yield loss.

Corn response to tillage and side‐dress nitrogen management on claypan soil

AbstractSince information islimited regarding N management and tillage options for corn (Zea mays L.) grown on claypan soil in the eastern Great Plains, the objective of this study was to determine the effect of preplant and side‐dress N applications on corn grown in conventional‐ and no‐till systems. The yield penalty for no‐till grown corn was nearly 20% due partially to an 8% stand reduction, but also to lower kernel weight and kernels ear–1 than with conventional till. These yield and yield component reductions with no‐till may be because of lower dry matter production and N uptake throughout the growing season. The general lack of interactions suggest that N management system effects on corn were not influenced by tillage system selection. Fertilizing with N more than doubled corn yields primarily by nearly doubling the number of kernels ear–1, but with additional increases in kernel weight and average number of ears plant–1. Averaged over years, split‐N resulted in up to 15% greater yield, and additional side‐dress N resulted in up to 28% greater yield than when 168 kg N ha–1 was applied only at preplant, with no yield reduction for delaying side‐dress application from V6 to V10. The relationship of relative N uptake to relative corn yield approached a direct 1:1 relationship by R1 (silking). The decision of whether to split‐apply fertilizer N or to add additional N, regardless of tillage system, will likely be influenced by economic factors, but side‐dress N applications may extended to the V10 stage with no yield penalty.

QUALITY OF SOWING AND DEVELOPMENT OF MAIZE AS A FUNCTION OF BLACK OAT MANAGEMENT METHODS APPLIED IN DIFFERENT PERIODS BEFORE MAIZE SOWING

The correct straw management in no-tillage system is necessary and has demonstrated to be an excellent alternative to improve sowing quality. Cover crop management periods may compromise the performance of planters and the productivity of the successor crop. The objective of this study was to evaluate the effect of black oat management methods, carried out in different periods before maize planting, on the quality of sowing and development of the crop. Two experiments were conducted in the municipality of Coimbra, MG: the first in 2013 and the second in 2016. Randomized block design was used in both experiments, in split-plot arrangement (4x3), with four replications. The plots consisted of four black oat management periods (21, 14, 7 and 0 days before sowing) and the subplots consisted of three black oat management methods (desiccated, rolled and cleared). The plants were managed in the flowering stage. The characteristics evaluated were: average, faulty, double and normal spacing between plants; sowing depth; emergence speed index; plant stand; and uniformity of plant development in V5 stage. In both experiments, the desiccated black oat presented lower emergence speed index, plant stand and uniformity of plant development. The mechanical managements of black oat, regardless of the period before maize planting, improve the quality of maize sowing, with significant reduction of faulty and double spacing, and promote proper plant development.

TOP-DRESSING NITROGEN DOSES IN MAIZE SOWN IN SINGLE AND DOUBLE ROWS AND CULTIVATED IN WINTER

Due to the intensification of production in irrigated areas, maize hasbeen sown in winter, enabling three seasons in one agricultural year. The objective of this study was to evaluate the agronomic performance of maize under irrigation and cultivated in winter under different plant arrangements (single and doublerow) under top-dressing nitrogen doses. The experimental design used was in randomized blocks in a split-plot scheme, with four replicates. Plots were formed by sowing systems single and double rows and subplots were formed by four top-dressing N doses: 0 kg ha-1 of N; 80 kg ha-1 of N with single application in phenological stage V3; 160 kg ha-1 of N with application of 80 kg ha-1 in V3 and V6, and 240 kg ha-1 of N with application of 80 kg ha-1 in stages V3, V6 and V8. The single-row sowing system led to higher grain yield compared to maize grown in the double-row system. Maize grain yield showed progressive linear increments with increasing top-dressing N doses, reaching 11,089 kg ha-1 of grains with the maximum studied dose of 240 kg ha-1 of N. Sowing systems in single and double rows do not differ with respect to the use of top-dressing N.

Spatial and temporal distribution of mung bean (Vigna radiata) and soybean (Glycine max) roots

Spatial and temporal distribution of roots of mung bean and soybean originated from different geographical backgrounds is an important scientific issue. The aim of this study was to research the spatial and temporal distribution of roots system of soybean cultivar ‘Hefeng55’ and mung bean cultivar ‘Jilv7’ which can elucidate differences between soybean roots and mung bean roots in the key spatial and temporal locations. The roots at V6, R2, R4, R5, R6, and R7 stages were collected to acquire data of root length, root surface area, root volume and root dry weight. 49.8%, 11.7%, 13.2%, 14.7% and 10.6% of soybean roots and 57.8%, 10.7%, 11.2%, 11.9% and 8.4% of mung bean roots were in 0-5, 5-10, 10-15, 15-20 and 20-25 cm horizontal soil layers, respectively; 79.2%, 11.5%, 4.3%, 1.8%, 1.1%, 1.0% and 1.1% of soybean roots and 70.0%, 12.3%, 8.0%, 3.0%, 1.6%, 1.7% and 3.4% of mung bean roots were in 0-20, 20-40, 40-60, 60-80, 80-100, 100-120 and 120-140 cm vertical soil layers, respectively. Compared with mung bean, soybean had a much larger root system during development. In horizontal direction, soybean root tended to be more laterally developed, but the distribution of mung bean root was more uniform in vertical direction. With a greater root surface area to weight ratio (AWR), mung bean had a finer root system than soybean. These findings can help to clarify the four-dimensional spatial and temporal distribution characteristics of legumes and may provide reference for production practice of soybean and mung bean in the future.

A Global Screening Assay to Select for Maize Phenotypes with a High Tolerance or Resistance to Fusarium verticillioides (Sacc.) Nirenberg Rots

Fusarium verticillioides (Sacc.) Nirenberg (Fv) causes rots in maize around the world and produces mycotoxins that contaminate grains, making this species a significant health concern for both animals and humans. One of the best approaches to address rots is to identify highly tolerant or resistant genotypes that can be used for genetic improvement. The aim of the study was to evaluate dose-response assays to tolerance or resistance for Fv rots throughout the maize life cycle. These tests assessed the effects of Fv during post-germination development and the seedling (V2) stage by seed infection, the plantlet (V4) stage by substrate infection, and in the reproductive phase in maize stalks (R2 stage) and ears (R6 stage) by R1 stage inoculation. In all assays, the doses were effective at distinguishing contrasting phenotypes. Severity, root fresh weight, and aerial length were the most informative parameters at the V2 and V4 stages. Evaluation of the stalk necrosis area between and within the internodes of susceptible genotypes revealed significant differences among doses, and a positive correlation between necrosis and conidia concentration was observed in internodes. Injecting eight million conidia in the ear was sufficient for selecting different phenotypes. A total of 85% of the genotypes conserved their same capacity to respond to Fv infection throughout the maize life cycle, so that screening at the early vegetative stage (e.g., V2) could be useful for distinguishing contrasting phenotypes in the reproductive stage. Implementing these screening assays in a maize breeding program could be valuable for classifying the degrees of resilience of maize germplasms to Fv rots. This global screening has the potential to be employed to select against other Fusarium species.

A Novel Nomogram Model Based on Cone-Beam CT Radiomics Analysis Technology for Predicting Radiation Pneumonitis in Esophageal Cancer Patients Undergoing Radiotherapy.

PurposeWe quantitatively analyzed the characteristics of cone-beam computed tomography (CBCT) radiomics in different periods during radiotherapy (RT) and then built a novel nomogram model integrating clinical features and dosimetric parameters for predicting radiation pneumonitis (RP) in patients with esophageal squamous cell carcinoma (ESCC).MethodsAt our institute, a retrospective study was conducted on 96 ESCC patients for whom we had complete clinical feature and dosimetric parameter data. CBCT images of each patient in three different periods of RT were obtained, the images were segmented using both lungs as the region of interest (ROI), and 851 image features were extracted. The least absolute shrinkage selection operator (LASSO) was applied to identify candidate radiomics features, and logistic regression analyses were applied to construct the rad-score. The optimal period for the rad-score, clinical features, and dosimetric parameters were selected to construct the nomogram model and then the receiver operating characteristic (ROC) curve was used to evaluate the prediction capacity of the model. Calibration curves and decision curves were used to demonstrate the discriminatory and clinical benefit ratios, respectively.ResultsThe relative volume of total lung treated with ≥5 Gy (V5), mean lung dose (MLD), and tumor stage were independent predictors of RP and were finally incorporated into the nomogram. When the three time periods were modeled, the first period was better than the others. In the primary cohort, the area under the ROC curve (AUC) was 0.700 (95% confidence interval (CI) 0.568–0.832), and in the independent validation cohort, the AUC was 0.765 (95% CI 0.588–0.941). In the nomogram model that integrates clinical features and dosimetric parameters, the AUC in the primary cohort was 0.836 (95% CI 0.700–0.918), and the AUC in the validation cohort was 0.905 (95% CI 0.799–1.000). The nomogram model exhibits excellent performance. Calibration curves indicate a favorable consistency between the nomogram prediction and the actual outcomes. The decision curve exhibits satisfactory clinical utility.ConclusionThe radiomics model based on early lung CBCT is a potentially valuable tool for predicting RP. V5, MLD, and tumor stage have certain predictive effects for RP. The developed nomogram model has a better prediction ability than any of the other predictors and can be used as a quantitative model to predict RP.

Stimulation action of mefenpyr-diethyl on soybean, wheat, and signal grass plants

Mefenpyr-diethyl is a safener used for protection of cereal plants under applications of ACCase and ALS inhibitor herbicides. Current studies are describing safeners using a new approach, relating these products to stimulation action on plants. The objective of this work was to evaluate the stimulation action of mefenpyr-diethyl on soybean, wheat, and signal grass plants. The experiment was conducted in a greenhouse, under a completely randomized design, with four replications, in two seasons. Mefenpyr-diethyl (50 g a.i. ha−1) was applied on soybean plants (at V4 stage), and wheat and signal grass plants (both with 15 cm height). The variables evaluated were plant height, dry matter, and lipid content of the three species, and number of tillers of wheat and signal grass plants. The application of mefenpyr-diethyl in the first season increased the number of tillers of wheat and height of soybean plants. The soybean presented 24 and 14% more dry matter than the control in the first and second season, respectively, and 0.5% more lipid content in plants treated with mefenpyr-diethyl. These results show the stimulation action of mefenpyr-diethyl on wheat and soybean plants, denoting its potential for growth promotion and indicating the need for studies with this approach. No effect was found for the signal grass plants.

Can low doses of glyphosate stimulate common bean growth?

Plant growth can be stimulated by low doses of glyphosate. The objective of this work was to evaluate the effect of low doses of glyphosate and sowing season on the growth of the early cycle common bean. Two experiments were conducted in the field, the first in the winter and the second in the wet season, with the early cycle common bean cultivar IAC Imperador. The experimental design was a randomized complete block design, consisting of low doses of glyphosate applied on phenological stage V4, with four replications. Environmental conditions, such as air temperature, interfered in the early cycle common bean response to low doses of glyphosate. In the winter season, a dose of 36 g a.e. ha−1 promoted growth in the common bean, and a dose of 7.2 g a.e. ha−1 improved the harvest index. In the wet season, there was no growth stimulus, and the harvest index increased with a dose of 36 g a.e. ha−1. The harvest index was the only characteristic improved in both seasons, but with different doses. Our study indicates that growth characteristics of early cycle common bean are stimulated by low doses of glyphosate, but this response is dependent on the growing environment.

Flow investigation of cross-flow turbine using CFD method

Cross-flow turbine is one of prime mover type that is simple, capable to extract water power and easy to be manufactured. The runner is working at 2 stages. The need of high momentum has lead researchers to design water nozzle, blades, as well as the set-up between nozzle and runner. High momentum water nozzle and cross-flow runner has been designed individually with the same design criteria. Unfortunately, experimental testing may not gain specific flow pattern inside the nozzle and the runner. The purpose of this study is to investigate the flow pattern inside the nozzle, runner using CFD method, Ansys 2019 R3 academic version. The CFD simulation done 3-dimensionally with 5 nozzle inlet velocity variations: 2 m/s, 3 m/s, 4 m/s, 5 m/s and 6,487 m/s. The fluid is assumed to be 1 phase, using mesh with 17.750 nodes, inlet fluid pressure 1,05 Pa, and temperature 24,85°C. The results showed that the lowest velocity and pressure for variation 1 at 1st stage (v1) = 6,65 m/s and (p1) = -11931,5 Pa, and the highest velocity and pressure at 1st stage (v5) = 21,72 m/s and (p5) = -127521 Pa. At 2nd stage, variation 1 and 5 resulting velocity (v1) = 1,78 m/s and (p1) 593,264 Pa, (v5) = 5,83 m/s and (p5) = 6360,32 Pa respectively. The main different of the flow pattern between 5 inlet velocity variations is the final flow thickness inside the runner get thicker at higher velocity, which is assumed to gain more rotational velocity.

MicroRNA transcriptomic analysis of the sixth leaf of maize (Zea mays L.) revealed a regulatory mechanism of jointing stage heterosis

BackgroundZhengdan 958 (Zheng 58 × Chang 7–2), a commercial hybrid that is produced in a large area in China, is the result of the successful use of the heterotic pattern of Reid × Tang-SPT. The jointing stage of maize is the key period from vegetative to reproductive growth, which determines development at later stages and heterosis to a certain degree. MicroRNAs (miRNAs) play vital roles in the regulation of plant development, but how they function in the sixth leaf at the six-leaf (V6) stage to influence jointing stage heterosis is still unclear.ResultOur objective was to study miRNAs in four hybrid combinations developed in accordance with the Reid × Tang-SPT pattern, Zhengdan 958, Anyu 5 (Ye 478 × Chang 7–2), Ye 478 × Huangzaosi, Zheng 58 × Huangzaosi, and their parental inbred lines to explore the mechanism related to heterosis. A total of 234 miRNAs were identified in the sixth leaf at the V6 stage, and 85 miRNAs were differentially expressed between the hybrid combinations and their parental inbred lines. Most of the differentially expressed miRNAs were non-additively expressed, which indicates that miRNAs may participate in heterosis at the jointing stage. miR164, miR1432 and miR528 families were repressed in the four hybrid combinations, and some miRNAs, such as miR156, miR399, and miR395 families, exhibited different expression trends in different hybrid combinations, which may result in varying effects on the heterosis regulatory mechanism.ConclusionsThe potential targets of the identified miRNAs are related to photosynthesis, the response to plant hormones, and nutrient use. Different hybrid combinations employ different mature miRNAs of the same miRNA family and exhibit different expression trends that may result in enhanced or repressed gene expression to regulate heterosis. Taken together, our results reveal a miRNA-mediated network that plays a key role in jointing stage heterosis via posttranscriptional regulation.

Enhanced Tolerance to Cold in Common Bean Treated with Biostimulant

Plants exposed to suboptimal temperatures suffer damage to physiological processes, growth, development and yield. Acting as enhancers of physiological and metabolic performance of plants, biostimulants have been used to mitigate crop damage caused by abiotic stresses. This study aimed to determine which formulation and dosage of FH Attivus® biostimulant have the best effects on the development of bean plants exposed to suboptimal temperatures (<20 °C). The experiment was conducted in a greenhouse under suboptimal temperatures in a randomized block design with four replications and ten treatments, consisting of three formulations and dosages of the biostimulant, applied at V4 stage, besides a control without biostimulant application. Growth, physiological and biochemical variables were evaluated. The application of biostimulant made bean plants more tolerant to low temperatures by maintaining CO2 net assimilation rate (A) and increasing the activity of antioxidant enzymes. The relative chlorophyll content (SPAD index), PSII effective quantum yield of linear electron flux (ϕPSII), apparent electron transport rate (ETR) and photochemical extinction coefficient (qP) were higher in all treatments compared to the control, as well as the lowest values of A and ETR were observed in the control. In addition, the activities of all evaluated antioxidant enzymes were superior to the control at the lowest dosages of formulation 2, and at all dosages of formulation 3, indicating, in these treatments, greater protection of cells against oxidative damage. The use of biostimulant is, therefore, a management that makes plants less susceptible to low temperatures in the growing environment.

Technical and economic viability of biostimulant applied in post-emergence of common bean

A intensificação da produção agrícola aumenta a busca por manejos que aumentem a produtividade das culturas, incluindo uso de bioestimulantes vegetais. O objetivo deste trabalho foi avaliar a viabilidade técnica e econômica do bioestimulante Stimulate®, aplicado nos estágios V4 ou R5 da cultura do feijão. Dois experimentos foram conduzidos em diferentes épocas (estação das águas e da seca) em Londrina, PR, no ano agrícola de 2016/17. Os tratamentos foram organizados em esquema fatorial (5x2) e consistiram em doses do bioestimulante Stimulate® (0; 500; 1.000; 1.500 e 2.000 mL ha-¹) e estágios fenológicos da cultura no momento da aplicação (V4 e R5). O rendimento de grãos e os componentes de rendimento da cultura foram avaliados e uma análise econômica foi realizada. Na estação das águas, a aplicação do bioestimulante na dose de 500 mL ha-1 apresentou os melhores resultados, resultando em produtividade 226 Kg ha-1 superior ao controle e aumento de rentabilidade em 6,22%. Na estação seca, a maior produtividade também foi alcançada com a aplicação de 500 mL ha-1, proporcionando uma produtividade 39,4% maior que o controle e um aumento de 36,4% na margem de lucro. Não foram observadas diferenças entre os estágios de aplicação para a variável rendimento de grãos. No entanto, para alguns componentes de rendimento, a aplicação em R5 resultou em melhores resultados. A estação das águas foi mais produtiva, com produtividade média de 3.630 kg ha-1, enquanto na estação seca a média foi de 1.360 kg ha-1. O uso do bioestimulante foi técnicamente e economicamente viável quando aplicado na dose de 500 mL ha-1 em ambos estádios do feijão comum (V4 ou R5) e épocas de cultivo (estação das águas e da seca).

New insights on molybdenum fertilization in common bean under no-tillage system: rates and application time to obtain high vigor seeds

Molybdenum (Mo) is a key element in the N fixing and assimilation processes in leguminous plants. This study aimed to evaluate the effects of Mo fertilization on the yield and seed vigor of the common bean. Molybdenum was applied at six rates (0, 20, 40, 80, 120 and 160 g ha−1) in field trials over 2 consecutive years (2015 and 2016). Foliar applications were performed during the phenological stages V4 (4th trifoliolate leaf unfolded) and R1 (early flowering). The SPAD index, height of first pod insertion, number of pods per plant, number of seeds per pod, weight of 100 seeds, yield and seed vigor were determined. Molybdenum affected the production of reproductive organs only in the second agricultural year. Application of Mo at T-V4 resulted in an increase in the number of pods per plant (11%), and at 120 g ha−1, there was an increase (41%) in the number of seeds per pod, but this did not result in a yield seed increase. Molybdenum applied at the T-V4 phase reduced electrical conductivity in the first year of the experiment at rates of 40 g ha−1 (17%) and 160 g ha−1 (13%). In the second agricultural year, Mo applied at the T-R1 phase reduced in 44% the electrical conductivity, as well as the application of 20 g ha−1 also at the T-R1 phase increased seed germination (28%), seedling length (8%), and length of the primary root (10%). Different responses to the Mo application time and dose between the experimental years suggest that common bean plants recycle Mo. Molybdenum applied in the first agricultural year may have satisfied the initial Mo demand of the common beans in the second year of crop due it's low Mo requirement. This study show that foliar Mo application is an important strategy to achieve sustainable production of higher quality seeds of common bean.

NITROGEN RATES AND SOWING DATES INFLUENCE THE SEVERITY OF WHITE SPOT DISEASE AND GRAIN YIELD OF MAIZE

The objective of this study was to analyze the effects of nitrogen rates and sowing dates on the severity of white spot disease (WSD) in first season maize hybrids, and their correlation with relative chlorophyll content, thousand grain weight and yield. The experiment was set in a randomized block design with treatments arranged in split-split plots. Two hybrids were tested in the main plots: AG9025 PRO3 (super early) and 30F53 VYH (early). Two sowing dates were evaluated in the split plots: preferential (9/20/2016) and late (12/05/2016). Four nitrogen rates were applied in the split-split plots. Nitrogen rates were top-dressed at the V4, V8 and V12 vegetative stages. The relative chlorophyll content reading was performed at VT stage. The quantification of WSD severity was made at R6, using diagrammatic scale. The AG9025 PRO3 hybrid showed higher average WSD severity (17.7%) than the 30F53 VYH (9.3%). The preferential sowing date showed lower severity (2.2%) compared to the late sowing date (31.4%). There was a significant positive correlation between the disease severity and the relative chlorophyll content, thousand grain weight and grain yield, except for the 30F53 VYH hybrid on the late sowing date. The hybrid AG9025 PRO3 showed increase in WSD severity when the highest nitrogen rates were applied, on both sowing dates. The effect of N rates on WSD was not significant for the 30F53 VYH hybrid. The late sowing time generates greater disease severity. The AG9025 PRO3 hybrid is more susceptible and the severity of its white spot is increased with the increment in N doses. There is a positive correlation between the relative chlorophyll content, disease severity, yield and thousand grain weight.

AGRONOMIC PERFORMANCE OF MAIZE UNDER Azospirillum brasilense INOCULATION AND TOP-DRESSING NITROGEN FERTILIZATION

Maize inoculation with bacteria of the genus Azospirillum can reduce the consumption of nitrogen fertilizers to obtain maximum grain yield. In this context, the aim was to evaluate the effect of inoculation with Azospirillum brasilense associated with nitrogen fertilization on the maize agronomic performance. A randomized block design was used in a split-plot scheme with four replicates. Four inoculation managements with Azospirillum brasilense (T0 - control without inoculation; TC2 - seed box inoculation, 200x108 viable cells ha-1; TC3 - seed box inoculation, 400x108 viable cells ha-1; TS1 - previous inoculation of the seeds, 600x108 viable cells ha-1) associated with four top-dressing N doses (0, 60, 120 and 180 kg ha-1), applied at maize stage V6 by urea. Inoculation with Azospirillum brasilense associated with top-dressing nitrogen fertilization increases the number of grain rows per ear, number of grains per row, number of grains per ear and grain yield of maize, mainly due to its positive effects on plant nutrition. Managements with seed box inoculation with 400x108 viable cells per ha (TC3) and inoculation in seed pre-treatment (TS1) are the most recommended for maize.