Impact of fungicide application volume on ASIAN rust control and soybean crop yield

European Journal of Plant Pathology - Multisite fungicides are an anti-resistance strategy to control Phakopsora pachyrhizi. Among the protective fungicides, mancozeb is a fungicide that has been...     

Grapevine anthracnose in berries causes biochemical and enzymatic alterations

European Journal of Plant Pathology - Anthracnose (Elsinöe ampelina) is a major fungal disease in humid regions, causing damage to grapevine berries and decreasing fruit quality. Studies...     

Unmanned aerial vehicle to evaluate frost damage in coffee plants

Damage caused by frost on coffee plants can impact significantly in the reduction of crop quality and productivity. Remote sensing can be used to evaluate the damage caused by frost, providing precise and timely agricultural information to producers, assisting in decision making, and consequently minimizing production losses. In this context, this study aimed to evaluate the potential use of multispectral images obtained by unmanned aerial vehicle (UAV) to analyze and identify damage caused by frost in coffee plants in different climatic favorability zones. Visual evaluations of frost damage and chlorophyll content quantification were carried out in a commercial coffee plantation in Southern Minas Gerais, Brazil. The images were obtained from a multispectral camera coupled to a UAV with rotating wings. The results obtained demonstrated that the vegetation indices had a strong relationship and high accuracy with the frost damage. Among the indices studied the normalized difference vegetation index (NDVI) was the one that had better performances (r?=?? 0.89, R²?=?0.79, MAE?=?10.87 e RMSE?=?14.35). In a simple way, this study demonstrated that multispectral images, obtained from UAV, can provide a fast, continuous, and accessible method to identify and evaluate frost damage in coffee plants. This information is essential for the coffee producer for decision-making and adequate crop management.

     

Irrigation,nitrogen and gypsum effects on specific gravity and internal defects of Atlantic potatoes

Irrigation, nitrogen and gypsum were investigated in a 3-year study to determine their influence on specific gravity and internal physiological defects. Excess irrigation during August and September reduced specific gravity, increased the incidence of hollow heart, and in some years, internal brown spot. Tuber yields were not significantly affected by excess irrigation. Exclusion of late season irrigation, however, significantly reduced tuber yields. No consistent yield response to nitrogen was evident, but a response up to 168 kg/ha was observed in 1987. Nitrogen rate did not effect hollow heart, internal brown spot or chip color. The incidence of internal brown spot in the tubers of check treatments was quite variable from year to year, and ranged from 8 to 21%. The lowest incidence of internal brown spot observed in 1989 coincided with the highest calcium levels in the tuber peel. Although gypsum treated potatoes had reduced incidence of internal brown spot, the effects were partial and inconsistent. Significant increases in peel and petiole calcium concentrations in the gypsum treated plots only occurred in one year. The peel calcium levels appeared to be influenced more by the season and to a lesser extent by gypsum. Gypsum applications produced no effects on total or US#1 tuber yield, specific gravity, hollow heart, or chip color. Preliminary data also suggested that gypsum did not markedly influence the incidence of blackspot. Based on this study, a routine gypsum application to improve the tuber quality of the variety Atlantic is not recommended.     

Nitrogen Use Efficiency in Cacao Genotypes

Cacao (Theobroma cacao L) is mostly grown on soils with low natural fertility. On such soils nitrogen (N) is one of the most yield limiting nutrients for cacao. Information is lacking on N use efficiency in cacao. A greenhouse experiment was conducted to evaluate growth response and N use efficiency by two cacao genotypes. The genotypes used were TSH-565 and ICS-9 and N rates adapted were 0, 120, 240, 360, and 480 mg N /pot. In both genotypes, increasing levels of applied N improved growth (stem girth, dry weight of shoot and roots and shoot/root ratio), and concentration and uptake of N. Genotypes differed significantly for stem girth and ICS -9 produced greater stem girth compared with TSH-565. Nitrogen uptake had a linear relationship with root dry weight of the two genotypes. In both genotypes, increasing levels of applied N overall increased N-uptake efficiency (NEFF = N concentration in shoot x shoot/root), but decreased N-use efficiency by shoot and roots (NUE = g dry matter of shoot or root/mg N) and N-use efficiency of carbohydrate (NUEC = mg of total carbohydrates in shoot/mg of N in shoot). Both genotypes responded differently to applied N, despite the existence of close genetic relatedness between them. The method used here appears to be suitable method for identification of cacao genotypes that are efficient in uptake and utilization of N.     

ALUMINUM TOXICITY IN CORN PLANTS CULTIVATED WITH LOW AND HIGH IONIC STRENGTH NUTRIENT SOLUTIONS

The objective of the present study was to evaluate the phytotoxic effect of aluminum (Al) in corn plants in nutrient solution under high ionic strength (0.0094 uM) and low ionic strength (0.00001 uM). Regarding the low ionic strengths, nutrient solution was added daily until the end of the experimental period. The findings showed that the pH of the nutrient solution reduced with the increase in Al concentration, under both high and low ionic strengths solutions. Electrical conductivity of the nutrient solution increased with Al concentrations only in the solution with low ionic strength, demonstrating that the plant was more sensible to the element toxicity, thus reducing its growth and absorption of nutrients. The production of the total dry mass of corn was affected by the increase of Al concentration in the solution only under low ionic strengths, which reinforces the greater activity and absorption of the element under such condition.     

Macronutrient deficiency and anatomic modifications in crambe leaves

Abstract

This study had the objective of assessing growth, deficiency symptoms and leaf anatomy of crambe plants submitted to macronutrient availability. The experimental design was the complete randomized with four replications. The first treatment consisted of cultivating crambe plants in a nutrient solution completed with N, P, K, Ca, Mg, and S. Using the diagnosis by subtraction, the other treatments consisted of the same solution with individual omission of each nutrient, totaling seven treatments. Supplement of different solutions took place two weeks after emergence. One week forward, visual symptoms of deficiency started to be evaluated. By the end of the experiment, the number of leaves, number of branches, shoot dry matter and leaf anatomic parameters were evaluated. Nutrient deficiency limited shoot dry matter in the following order: N?>?Ca?>?P>Mg?>?S?>?K. Subtracting Ca from the solution was most limiting to crambe growth once plants did not even reach reproductive stages. Individual subtractions of each macronutrient anatomically altered crambe leaves, especially omitting Ca, K, and S, which reduced tissue thickness.     

Mobilization of seed reserves pretreated with H2O2 during germination and establishment of sunflower seedlings under salinity

Abstract

Several studies have shown hydrogen peroxide (H₂O₂) as a metabolic messenger that increases plant tolerance to various stress conditions. However, little is known about its effect on the mobilization of seed reserves in the establishment of seedlings. Thus, this study aimed to evaluate the effect of pretreatment with H₂O₂ in salt-tolerance and mobilization of reserves during the germination of seeds and establishment of sunflower seedlings. Seeds were pre-imbibed for 24?hr in solutions containing: deionized water (control); H₂O₂ (1?mM); NaCl (100?mM). Subsequently, seeds were distributed on germitest paper, moistened with deionized water or saline solution (100?mM NaCl). In seedlings not pretreated with H₂O₂, the salinity increased Na⁺ and Cl^? ions contents and reduced the growth of sunflower seedlings. However, pretreatment of seeds with H₂O₂ reduced the negative effect of salinity, promoted an increase in salt-tolerance by the reduction of Na⁺ and Cl^? uptake, lower energy cost for osmoprotection by compatible solutes accumulation, and by the higher equilibrium in the mobilization of the cotyledon reserves for the development of the embryonic axis.     

Fulvic acid in foliar spray is more effective than humic acid via soil in improving coffee seedlings growth

ABSTRACT

Humic (HA) and fulvic (FA) acids improve the nutrient availability and uptake by plants but some aspects of their agronomic use still need to be clarified. The effects of HA soil application and FA foliar application on the growth, Zn and B uptake by coffee seedlings were evaluated. HA was added to an Oxisol at concentrations 0, 10, 25, 50, 75 and 100 mg kg^?1 (C-HA), in both limed (pH 6.2) and overlimed (pH 7.2) conditions. FA (0, 0.2, 0.5 and 1 g L^?1 C-FA) was applied to coffee leaves in three different application modes (M): with 0.3% Zn and 0.6% B supplied via foliar (M₁), 0.6% B and 1.2% Zn supplied via foliar (M₂) and 1.2 mg kg^?1 B and 6 mg kg^?1 Zn supplied via soil (M₃). HA addition in soil significantly (p < 0.05) reduced leaf B and Zn accumulation and coffee growth in both pH conditions. In the M₁ and M₂, FA application significantly (p < 0.05) increased the shoot growth at 0.59 and 0.45 g L^?1 and B accumulation at 0.96 and 0.45 g L^?1 C-FA. Foliar application of C-FA, instead soil application of C-HA, is a suitable practice to improve coffee seedlings growth and nutrition on Oxisol.     

High K+ supply avoids Na+ toxicity and improves photosynthesis by allowing favorable K+ : Na+ ratios through the inhibition of Na+ uptake and transport to the shoots of Jatropha curcas plants

This study assessed the relationships between external K⁺ supply and K⁺ : Na⁺ ratios associated with Na⁺ toxicity in Jatropha curcas. Plants were exposed to increasing external K⁺ concentrations (6.25, 12.5, 25, 37.5, and 50 mM), combined with 50 mM NaCl in a nutrient solution. Photosynthesis progressively increased as the external K⁺ : Na⁺ ratios increased up to 0.75. The increase of photosynthesis and plant dry matter correlated positively with K⁺ : Na⁺ in xylem and leaves. The transport rates of K⁺ and Na⁺ from roots to xylem and leaves were inversely correlated. These ions presented an antagonistic pattern of accumulation in all organs. Maximum rates of photosynthesis and plant growth occurred with leaf K⁺ : Na⁺ ratios that ranged from 1.0 to 2.0, indicating that this parameter in leaves might be a good indicator for a favorable K⁺ homeostasis under salinity conditions. The higher K⁺ affinity and selectivity compared with Na⁺ in all organs associated with higher xylem flux and transport to shoots are essential for maintaining adequate K⁺ : Na⁺ ratios at the whole‐plant level. These characteristics, combined with adequate K⁺ concentrations, allow J. curcas to sustain high rates of photosynthesis and growth even under toxic NaCl levels.