V6 Stage Research Articles

Estimating the Impacts of Plant Internal Nitrogen Deficit at Key Top Dressing Stages on Corn Productivity and Intercepted Photosynthetic Active Radiation.

Accurate and timely appraisal of plant nitrogen (N) demand is imperative to regulate the canopy structure and corn production. The strength and time of plant N deficit can be quantified by critical N concentration. The study was aimed to analyze nitrogen nutrition index (NNI), nitrogen deficit content (NDC), plant nitrogen productivity (PNP), and a fraction of intercepted photosynthetic active radiation (FIPAR) across different N treatments and to develop NNI-NDC, NNI-PNP, NNI-FIPAR, NDC-PNP, and NDC-FIPAR relationships from V6 to V12 stages of corn to quantify the suitable PNP and FIPAR values under the optimal plant N condition. Four multi-N rates (0, 75, 90, 150, 180, 225, 270, and 300 kg N ha−1) field experiments were conducted with two cultivars of corn in Henan province of China. Results indicated that N fertilization affected yield, plant biomass, plant N content, and leaf area index. The values of NNI and NDC were from 0.54 to 1.28 kg ha−1 and from −28.13 to 21.99 kg ha−1 under the different treatments of N rate, respectively. The NDC and NNI showed significantly negative relationships from V6 to V12 stages. The values of PNP and FIPAR increased gradually with the crop growth process. The PNP values gradually declined while the FIPAR values of every leaf layer increased with the increase of N supply. The NDC-PNP and NNI-FIPAR relationships were significantly positive; however, the relationships between NNI-PNP and NDC-FIPAR were significantly negative during the vegetative period of corn. The coefficient of determination (R2) based on NNI was better than that on NDC. The FIPAR values were ~0.35, 0.67, and 0.76% at the upper, middle, and bottom of leaf layers, respectively, and PNP values were ~39, 44, and 51 kg kg−1 at V6, V9, and V12 stages, respectively, when NNI and NDC values were equal to 1 and 0 kg ha−1, respectively. This study described the quantitative information about the effect of a plant's internal N deficit on plant N productivity and canopy light intercept. The projected results would assist in predicting the appropriate plant growth status during key N top-dressing stages of corn, which can optimize N application and improve N use efficiency.

Response of common bean to Rhizobium reinoculation in topdressing

ABSTRACT The response capacity of the bean to fix atmospheric nitrogen is questionable, mainly due to its inability to supply all the nitrogen in the flowering and grain filling phases when the crop needs it most. Thus, a new application of inoculant can keep the population of rhizobia in the soil at adequate levels, meeting all the nitrogen demands of the plant. This study aimed to investigate the nodulation capacity and the production of beans submitted to doses and reinoculation of Rhizobium in topdressing under field conditions in two growth stages. For this, an experiment was conducted using a randomized block design with four replicates in a 4 × 2 + 2 factorial scheme. The treatments consisted of the application of four doses of liquid inoculant containing Rhizobium tropici (SEMIA 4088), in the concentration 2 × 109 CFU g-1, in topdressing (0, 100, 200 and 400 mL ha-1), in two development stages (V4 and R5) of plants, and two additional treatments (inoculation via seed at a dose of 100 g of the product per 50 kg of seeds and mineral nitrogen fertilization at a dose of 16 kg ha-1 applied at sowing and 60 kg ha-1 in topdressing, divided into two stages, with half being applied at the stage V3 and the other half in V4 stage).The inoculant application increased the nodulation rates of bean cultivar BRS Cometa and the dry biomass produced by plants, using doses of 232 and 221 mL ha-1, respectively. The dose of 257mL ha-1 of the liquid inoculant applied in topdressing at the V4 stage, and the inoculation via seed provide greater common bean yield without supplementing mineral nitrogen.

Blockchain in Education - The Case of Language Learning

Abstract New technological developments, such as 5G networks, smart and interconnected devices, and the development of the Internet of Things (IoT), lead to a new reality in which the secure flow of data is non-negotiable. In this new reality, blockchain technology can play a crucial role, as it has the ability to provide the necessary background for the safe and inviolable operation of systems. Blockchain is a distributed ledger, in which information and data are stored and verified. These blocks of data do not have to be related to financial transactions but may concern any other type of data that needs to be securely recorded and not changed retrospectively. Although the first application of blockchain technology was about digital currency (Bitcoin), its usefulness is not limited to cryptocurrencies or the field of economics. Blockchain, especially in its last stage v3.0, has many applications in various sectors such as data storage, certification of products and services, government, insurance, health, science, and education. This paper focuses on the current and potential educational applications of blockchain and presents how this technology can be used to solve specific education problems. Nowadays, a variety of blockchain applications concerning the issue and storage of certificates and diplomas, the evaluation of learning outcomes, the support and the academic degree management, the protection of intellectual property, the cooperation between students and their professors, learning accreditation, payment for studies, formation of an academic passport (portfolio) or administration of the educational process are implemented in some HEI and institutions. The paper analyzes the features and advantages of blockchain technology, presents some of the current blockchain applications for education, as well as the benefits and challenges of using blockchain technology in the educational sector. Finally, special reference is made to applications related to the field of language learning.

Impact of delayed postemergence herbicide application on corn yield based on weed height, days after emergence, accumulated crop heat units, and corn growth stage

AbstractNine field experiments were conducted from 2017 to 2019 in Ontario to determine the impact of early weed interference on corn yield based on corn growth stage, days after emergence (DAE), accumulated crop heat units (CHU), and weed size. The predicted weed size at herbicide application that resulted in a 1%, 2.5%, 5%, 10%, 25%, and 50% yield loss in corn was estimated to be 1, 4, 11, 53, non-estimable (N est.*), and N est.* cm under low weed density and 3, 5, 7, 11, 27, and N est.* cm under high weed density, respectively. The predicted DAE at herbicide application time that resulted in a 1%, 2.5%, 5%, 10%, 25%, and 50% yield loss in corn was predicted to be 14, 20, 27, 44, N est.*, and N est.* DAE under low weed density and 5, 7, 11, 17, 25, and 59 DAE under high weed density, respectively. The predicted CHU from planting at herbicide application time that led to a 1%, 2.5%, 5%, 10%, 25%, and 50% yield loss in corn was 468, 636, 821, 1,271, N est.*, and N est.* CHU from planting under low weed density and 207, 283, 385, 551, 972, and 1,748 CHU from planting under high weed density, respectively. The predicted crop stage at herbicide application that led to a 1%, 2.5%, 5%, 10%, 25%, and 50% yield loss in corn was V5, V6, V7, V11, N est.*, and N est.* under low weed density and V1, V2, V3, V4, V8, and V14 under high weed density, respectively. Results indicate that weeds must be controlled before they reach 7 cm in height, prior to 11 d after crop emergence, prior to 385 accumulated CHU from emergence, or prior to the V3 stage under high weed density to avoid greater than 5% yield loss.

A Three-Year Plant Study of Salt-Tolerant Transgenic Maize Showed No Effects on Soil Enzyme Activity and Nematode Community.

The environmental effects of genetically modified crops are now a global concern. It is important to monitor the potential environmental impact of transgenic corn after commercial release. In rhizosphere soil, plant roots interact with soil enzymes and microfauna, which can be affected by the transgenes of genetically modified crops. To determine the long-term impact of transgenic plant cultivation, we conducted a field study for 3 consecutive years (2018–2020) and observed the enzyme activities and nematode populations in plots planted with transgenic maize BQ-2, non-transgenic wild-type maize (Qi319), and inbred line B73. We took soil samples from three cornfields at four different growth stages (V3, V9, R1, and R6 stages); determined soil dehydrogenase, urease, and sucrase activities; and collected and identified soil nematodes to the genus level. The results demonstrated seasonal variations in dehydrogenase, urease, and sucrase activities. However, there was a consistent trend of change. The generic composition and diversity indices of the soil nematodes did not significantly differ, although significant seasonal variation was found in the individual densities of the principal trophic groups and the diversity indices of the nematodes in all three cornfields. The results of the study suggest that a 3-year cultivation of transgenic corn had no significant effects on soil enzyme activity and the soil nematode community. This study provides a theoretical basis for the environmental impact monitoring of transgenic corn.

Mycorrhizal colonization associated with roots of field‐grown maize does not decline with increasing plant‐available phosphorus

AbstractMaize roots are colonized by arbuscular mycorrhizal fungi, but less mycorrhizal symbiosis is expected as the plant‐available phosphorus (P) concentration of soil increases, based on greenhouse and growth bench experiments. The objective of this study was to evaluate maize root colonization by arbuscular mycorrhizal fungi in a sandy loam soil with a gradient of plant‐available P concentrations resulting from P fertilizer inputs. The field experiment received inorganic and organic P fertilizers for 3 years, and this created a 20‐fold difference in the plant‐available P concentration, from 12 to 204 mg Mehlich‐3 extractable P kg−1. The proportion of maize roots colonized with arbuscular mycorrhizal fungi increased from 26 ± 2% during vegetative growth (V8 and VT growth stages) to 46 ± 2% in the reproductive R2 and R6 stages. The P fertilizer input did not affect maize root colonization by arbuscular mycorrhizal fungi. More arbuscular mycorrhizal fungi colonization of maize roots occurred in soil with increasing plant‐available P concentrations (r = .12, p = .05, n = 237), and this was associated with greater P uptake in the maize shoots (r = .53, p < .001, n = 240). We conclude that the root‐mycorrhizal symbiosis was more strongly related to maize growth than the plant‐available P concentration under field conditions.

Overexpression of ZmSPL12 confers enhanced lodging resistance through transcriptional regulation of D1 in maize.

Overexpression of ZmSPL12 confers enhanced lodging resistance through transcriptional regulation of D1 in maize.

Trinexapac-ethyl application time in the crop corn agronomic performance grown under different plant arrangements

Reduced row spacing promotes more uniform spatial distribution of plants in the field. However, the adoption of reduced row spacing only is possible with smaller plants, which may be obtained with the use of plant growth regulator. This study aimed to evaluate the agronomic performance of the first corn crop with Trinexapac-ethyl applied at the different plant development stages and grown under different row spacing, with the same plant population. The experiments were arranged in a split-plot randomized block design with four replications, with row spacing for the plots (0.45 and 0.90 m) and Trinexapac-ethyl (TE) application time to subplots (control without application, at the V3, V6, V9 and V12 phenological stages). The Trinexapacethyl application time interacted with row spacings changing the growth and yield performance of the corn crop. For 0.45 m spacing Trinexapac-ethyl application at V12 and for 0.90 m spacing application at V9 and V12 reduced plant height and ear height. Trinexapac-ethyl application at V9 for both row spacings changed the plant architecture without changing the ear length and grain yield.

Plant Nutrition Influences Resistant Maize Defense Responses to the Fall Armyworm (Spodoptera frugiperda)

Plants are often confronted by different groups of herbivores, which threaten their growth and reproduction. However, they are capable of mounting defenses against would-be attackers which may be heightened upon attack. Resistance to insects often varies among plant species, with different genotypes exhibiting unique patterns of chemical and physical defenses. Within this framework, plant access to nutrients may be critical for maximal functioning of resistance mechanisms and are likely to differ among plant genotypes. In this study, we aimed to test the hypothesis that access to nutrition would alter the expression of plant resistance to insects and alter insect performance in a manner consistent with fertilization regime. We used two maize (Zea mays) genotypes possessing different levels of resistance and the fall armyworm (Spodoptera frugiperda) as model systems. Plants were subjected to three fertilization regimes prior to assessing insect-mediated responses. Upon reaching V4 stage, maize plants were separated into two groups, one of which was infested with fall armyworm larvae to induce plant defenses. Plant tissue was collected and used in insect bioassays and to measure the expression of defense-related genes and proteins. Insect performance differed between the two plant genotypes substantially. For each genotype, fertilization altered larval performance, where lower fertilization rates hindered larval growth. Induction of plant defenses by prior herbivory substantially reduced naïve fall armyworm growth in both genotypes. The effects between fertilization and induced defenses were complex, with low fertilization reducing induced defenses in the resistant maize. Gene and protein expression patterns differed between the genotypes, with herbivory often increasing expression, but differing between fertilization levels. The soluble protein concentrations did not change across fertilization levels but was higher in the susceptible maize genotype. These results demonstrate the malleability of plant defenses and the cascading effects of plant nutrition on insect herbivory.

Mid-season proximal sensing for site-specific need-based fertilizer nitrogen management in spring maize

Canopy reflectance measurements using active optical sensors have emerged as potential solution to draw in-season nitrogen (N) topdressings in cereals. Site-specific need-based N management strategy using a GreenSeeker optical sensor was developed and evaluated in spring maize. Four field experiments were conducted at two locations during 2017 and 2018 to develop an algorithm, and two experiments during 2019 to validate the sensor-based application for improving N use efficiency (NUE) and grain yield. The sensor measurements made at V9 growth stage with R2 value of 0.61 obtained from the relation between in-season estimate of yield (INSEY) and grain yield rendered better corrective N rate for improving NUE and getting optimum grain yield, whereas sensor measurements at V6, V12 and VT growth stages were not reliable for the purpose. Applying N rate in two splits of 30 kg N ha−1 at planting and 45 kg N ha−1 at V6 growth stage was recommended before applying sensor based corrective N rate at V9 stage. Sensor guided N topdressing produced yields similar to those obtained by following the soil test-based N recommendations but with lower N rates. These results were also reflected in considerable increase in N recovery (8 _18%) and agronomic (4 _13.5 kg grain kg−1 N) efficiencies in comparison with soil test-based N recommendations, thereby signifying the usefulness of the sensor-based algorithm in optimizing need-based fertilizer N management in spring maize.

Biostimulants Increase Soybean Productivity in the Absence and Presence of Water Deficit in Southern Brazil

Biostimulants offer a potentially novel approach for the regulation/modification of physiological processes in plants to stimulate growth, to mitigate stress-induced limitations, and to increase yield. The objective of this work was to evaluate the influence of vegetable biostimulants in soybean crop subjected to different soil water conditions. The experiments were carried out in 2017/2018 and 2018/2019, in a completely randomized design (water deficit, combination of biostimulants, and application time). The combinations of biostimulants and time of application were: no combination (control); foliar application at stage V5; foliar application stages V5 and R1; seed treatment; seed treatment and V5 applications; and seed treatment, V5 and R1 applications. All the biostimulant combinations were moreover subject to either the presence or absence of water stress. Evaluations performed were maximum photochemical efficiency, pods per plant, seeds per pod, thousand grain mass, productivity, and incremental increases in performance of each biostimulant treatment. No differences were observed under water deficit in either season, and the use of biostimulants increased the thousand grain mass and final productivity. After two crop seasons with results in increasing yield, the application of biostimulants is recommended in three stages (TS + V5 + R1) for the best management of soybean crops.

Biological control of bacterial leaf streak of corn using systemic resistance-inducing Bacillus strains

Management options are needed for emerging bacterial diseases such as bacterial leaf streak of corn (maize), caused by Xanthomonas vasicola pv. vasculorum (Xvv). The objective of this study was to determine the potential for seed treatment with strains of Bacillus spp. to provide control of bacterial leaf streak. In two trials of a greenhouse pot experiment, B. pumilus R190 and B. subtilis 6051 were applied to corn seed prior to planting, and the plants were grown to V3 stage when they were inoculated with Xvv. Inoculation in Trial 1 was performed by streaking Xvv cells onto leaf surfaces, while leaves were sprayed with a bacterial cell suspension in Trial 2. In both trials, extensive lesion development occurred on leaves of the no-bacteria control 14 days after pathogen inoculation. Seed treatment with B. pumilus R190 reduced disease severity significantly by 85% and 56% compared to the control in Trial 1 and Trial 2, respectively. Disease severity was reduced by seed treatment with B. subtilis 6051 by 32% and 52% in Trial 1 and Trial 2, respectively, with the disease reduction being statistically significant only in Trial 2. The reduction in the foliar disease resulting from the application of bacteria to seed was an indication that induced systemic resistance was involved as the biological control mechanism. This is the first demonstration that root-colonizing bacteria have potential as biocontrol agents to suppress a foliar bacterial disease in corn.

Biochar amendment benefits 15N fertilizer retention and rhizosphere N enrichment in a maize-soil system

Biochar amendments regulate fertilizer nitrogen (N) transformation in soil and crop N uptake. To elucidate the effect of biochar amendment on the translocation of fertilizer N in a crop-soil system during crop growth, a maize pot experiment was conducted using an isotope tracer approach. The treatments were: without N application; 15N-labelled urea; and 15N-labeled urea plus biochar. During maize growth, biochar amendment increased root biomass, total crop N uptake, and urea N retention in soil. In bulk and rhizospheric soils, biochar amendment significantly (P < 0.05) increased urea N retention in soil total N (TN), microbial biomass N (MBN), particulate organic N (PON) and mineral associated total N (MTN) from the eighth leaf stage (V8) to physiological maturity (R6) and decreased fertilizer N retention in inorganic N and dissolved organic N from stages V8 to silking (R1). Relative to bulk soil, rhizospheric soil promoted urea N retention in TN, inorganic N, MBN, and MTN under both fertilizer treatments, and biochar application enlarged this difference for MBN; rhizospheric soil enhanced PON mineralization resulting in a significantly (P < 0.05) lower PON from stages R1 to R6 when compared with bulk soil, and biochar application retarded this mineralization. These findings unveiled that biochar application increased fertilizer N retention by increasing MBN, PON, and MTN and that biochar application benefited the enrichment of fertilizer N in rhizospheric soil.

Characterization of priming, induced resistance, and tolerance to Spodoptera frugiperda by silicon fertilization in maize genotypes

Fall armyworm (FAW) Spodoptera frugiperda is considered the main defoliating insect pest of maize in many countries. Silicon (Si) applied to plants has been shown to increase the resistance to insects, especially in grasses such as maize. This study characterized the effects of Si fertilization regarding priming, induced resistance, and tolerance to FAW in a landrace variety and hybrid of maize. Si was applied in soil of potted-plants as H4SiO4 at 2 t ha−1 when maize plants were at V2 stage, and when they reached V3 two FAW neonates were placed in the plant’s whorls to cause herbivory. FAW performance was evaluated on excised leaf sections in the laboratory and on plants with larvae infesting V4-stage plants in the greenhouse. Concentrations of H2O2, malondialdehyde, and Si, and the activities of antioxidant enzymes were recorded and correlated to Si-based responses on plant growth, and FAW injury and performance. As main results, there was reduced FAW injury and larval weight gain in Si-treated plants subjected to herbivory. Greater root dry mass was observed in the landrace variety with Si and without herbivory. Landrace plants showed higher shoot weights than the hybrid under FAW infestation. Si-fertilized plants showed higher H2O2 concentrations. The highest peroxidase activities occurred in Si-treated plants without herbivory, and the catalase and superoxide dismutase activities were highest in Si-treated plants without herbivory or herbivory-injured plants without Si. In conclusion, Si-based defense in maize to FAW involve mixed effects of priming and tolerance, and were more pronounced in the landrace variety.

Green bridge crops to manage corn nitrogen nutrition in the Southeastern Argentinean Pampas

An ecological intensification of agriculture through the use of green bridge crops (GBC) between cash crops is a way to improve resource use efficiency. This study aimed to assess vetch (Vicia villosa Roth.) (Ve), oat (Avena sativa L.) (Oa), Oa+Ve as GBC, and a control without GBC, with different termination dates (early and late), tillage systems (conventional tillage and no-tillage), and nitrogen (N)-fertilization to corn (Zea mays L.) (NF: 0 and 120 kg N ha−1) on soil N availability, and corn N uptake and yield. Three field experiments were carried out at the Southeastern Argentinean Pampas in 2012–2013, 2013–2014, and 2014–2015 on an Argiudoll. Corn and GBC aboveground dry matter and N accumulation and corn grain yield were determined. Soil nitrate-N at corn planting and V6 and anaerobically mineralizable N (AN) at corn planting were also determined. Water availability at corn planting was not limiting, whereas along corn cycle differed among years. The GBC terminated late accumulated more dry matter and N than those terminated early and Ve and Oa+Ve more N than Oa. Both early termination date and Ve tended to show higher nitrate-N at planting and at V6 stage. In general, NF improved corn behavior but response was different among GBC, being lower after Ve and Oa+Ve, and with late termination date. A simple model was fitted to predict corn relative yield based on nitrate-N at V6 stage, AN, GBC dry matter accumulation and C:N ratio. The model fitted allowed predicting relative corn grain yield and could be used as a tool to help N fertilization recommendation.

Root response of soybean genotypes to low phosphorus availability from juvenile to adult vegetative stages

ABSTRACT Due to the rapid exhaustion of global phosphorus (P) resources, P-efficient crops are required. In this study, we used various soybean genotypes collected from around the world and investigated the morphophysiological responses of their roots to low-P conditions at the cotyledon emergence (VE), unifoliate leaves emergence (VC), and fourth trifoliate leaflet emergence (V4) growth stages. First, we compared the growth of 81 soybean genotypes under different P conditions at the VC stage. The root morphology of most genotypes did not differ according to P conditions. However, GmWMC138 showed increased root weight under low-P conditions at the VC stage, and was therefore selected for further comparative analysis with genotypes with similar seed weights. Four selected genotypes were compared in terms of their seed storage P content and responses of plant growth and phytase and acid phosphatase activities to low-P conditions at the VE and VC stages. The inorganic-P (Pi) levels and shoot growth at the VE and VC stages of GmWMC138 were less affected by low-P conditions compared to the other genotypes. In this genotype, root fresh weight at the VC stage, phytase activity in roots at the VE stage, and acid phosphatase activity in roots at the VC stage increased under low-P conditions. The differences in these enzyme activities may have led to the maintenance of root Pi content and subsequent increase in the root fresh weight at the VC stage under low-P conditions. In addition, the low-P responses of growth and P content at the V4 stage were compared among the selected genotypes. In GmWMC138, fine-root length increased and total P content was maintained under low-P conditions compared to normal-P conditions. These results imply that in soybeans morphological changes in roots in response to low-P conditions at juvenile growth stages, such as the VE and VC stages, may contribute to P-deficiency tolerance in subsequent growth stages, such as the V4 stage.

Effect of herbicides on the activity of antioxidant enzymes and ALA-D in transgenic hybrid corn

A corn cultivar with resistance to 2,4-D, glyphosate, ammonium-glufosinate, and haloxyfop-R has been developed. However, it is known that the application of herbicides generally induces the accumulation of reactive oxygen species (ROS), which can cause oxidative damage to plants. In this study, we applied these herbicides in Enlist™ corn hybrids, in the doses recommended for weed control of herbicides alone and in mixtures, being 0, 670, 1080 400, and 60 g ha-1 a.e. of glyphosate, 2,4-D, ammonium-glufosinate, and haloxyfop-R, respectively. The experiment was conducted in a greenhouse at Universidade Federal da Fronteira Sul (UFFS), Erechim, RS, Brazil. The plants were grown in a soil and substrate mix (proportion of 1:1), in plastic vases (0.5 L). The design was completely randomized, with four replicates and two plants per replicate. The herbicides were sprayed 22 days after corn emergence (V2 stage). At seven days after the application, all plants were collected and macerated, then maintained in an ultra-freezer at -80 ºC until the biochemical analysis could be performed. The activity of antioxidant enzymes such as catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), ALA-D and the lipid peroxidation levels were evaluated to know the effects of herbicide application in these plants. The herbicides, especially the mixtures, increased the activity of the antioxidant enzymes that decompose H2O2, such as CAT and APX, and also caused an inhibition of the activity of GPX and ALA-D while promoting lipid peroxidation. This may be associated with the increased generation of H2O2, which was added to the production of other ROS, causing an overload of the antioxidant defense system of transgenic corn, resulting in damage to plant lipids

Waterlogging priming alleviates the oxidative damage, carbohydrate consumption, and yield loss in soybean (Glycine max) plants exposed to waterlogging.

In this study, we tested whether waterlogging priming at the vegetative stage would mitigate a subsequent waterlogging event at the reproductive stage in soybean [Glycine max (L.) Merr.]. Plants (V3 stage) were subjected to priming for 7days and then exposed to waterlogging stress for 5days (R2 stage) with non-primed plants. Roots and leaves were sampled on the fifth day of waterlogging and the second and fifth days of reoxygenation. Overall, priming decreased the H2 O2 concentration and lipid peroxidation in roots and leaves during waterlogging and reoxygenation. Priming also decreased the activity of antioxidative enzymes in roots and leaves and increased the foliar concentration of phenols and photosynthetic pigments. Additionally, priming decreased fermentation and alanine aminotransferase activity during waterlogging and reoxygenation. Finally, priming increased the concentration of amino acids, sucrose, and total soluble sugars in roots and leaves during waterlogging and reoxygenation. Thus, primed plants were higher and more productive than non-primed plants. Our study shows that priming alleviates oxidative stress, fermentation, and carbohydrate consumption in parallel to increase the yield of soybean plants exposed to waterlogging and reoxygenation.

Identification of sources of resistance to race 63-63 of Pseudocercospora griseola in common bean lines

Angular leaf spot (ALS), caused by the fungus Pseudocercospora griseola, is one of the most important foliar fungal diseases in common bean (Phaseolus vulgaris L.). The search for new sources of resistance to ALS is a promising activity in common bean breeding programs. In this study, the reaction of 416 germplasm accessions from the Universidade Federal de Lavras (UFLA) to P. griseola (race 63-63, the most important and most aggressive race) was assessed under greenhouse conditions (plants in the V2 stage, fully developed unifoliolate leaves). We identified 102 (24.5%) resistant and 314 (75.5%) susceptible accessions. Among the resistant lines, more than half are Carioca grain type lines. This study characterizes the resistance of a wide collection of common bean genotypes. The identification of new accessions resistant to P. griseola is an important step in common bean breeding programs. These lines can continually be incorporated in backcrosses to obtain cultivars resistant to ALS.

Evaluation of Soil Test Phosphorus Extractants and Tissue Analysis for Corn

The objective of this study was to evaluate the relationship of four different soil test phosphorus methods (Mehlich 3, Bray 1, Bray 2, and Haney H3A) for corn production, and determine critical P tissue concentration at different growing stages. The experiment was conducted at 12 locations, and the fertilizer treatments consisted of five phosphorus fertilizer rates applied by broadcast pre-plant. Soil samples were collected at 0- to 6-in. depth, then samples were collected before treatment application by block. Tissue samples were collected at the V6 and R1 growth stages. The relationship between the different soil test phosphorus methods and the R2 varies between 0.24–0.93. Mehlich 3 and Bray 1 have a higher correlation, and Bray 1 and Bray 2 have a lower correlation. Linear plateau determined the critical phosphorus levels for the V6 growth stage was 0.42%, and for the R1 stage was 0.22%. The relationship between the concentration at V6 and R1 was moderately correlated with R2 = 0.62, having a higher phosphorus concentration in the early stage.