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.     

Biocontrol of potato early blight and suppression of Alternaria grandis sporulation by Clonostachys spp.

Early blight, caused by Alternaria solani and A. grandis, severely affects potato crops around the world, and few management options apart from intensive fungicide use are available. In this work, we tested whether biocontrol treatments with different species of the mycoparasitic fungus Clonostachys could reduce early blight severity on the foliage of pot-grown potatoes of cultivar Ágata, and affect the survival and sporulation of the causal pathogen A. grandis. Twenty isolates from five Clonostachys species were screened in a preliminary biocontrol trial, and nine of them were selected and tested further in two confirmation trials. Treatments with three isolates from three species (C. chloroleuca, C. pseudochroleuca, C. rhizophaga) resulted in a significant reduction in disease severity in both confirmation trials, with control efficacy ranging from 88.7% to 92.9% in the first trial, and from 83.1% to 84.7% in the second trial. All Clonostachys isolates used in the confirmation trials survived on potato leaf tissues for at least 15 days, and resumed growth when subjected to high humidity, resulting in mycoparasitic overgrowth and significant reduction of the pathogen sporulation. Our results provide evidence that different species of Clonostachys, not only the ubiquitous C. rosea, are sources of useful candidates for the biocontrol of potato early blight and possibly other plant diseases caused by fungal pathogens.     

Target Spot Control and Modulation of the Physiology in Cucumber Using Phosphites and Chitosan

Phosphites and chitosan were evaluated in target spot control, nutrition and gas exchange in cucumbers. Three weekly sprayings of commercial products were conducted, and Corynespora cassiicola (causal agent of target spot) was inoculated in the second and third true leaves four days after the last spraying. Zn, Mn, K and Cu phosphites reduced the disease severity, but the treatments had no effect on the development of the plants and the accumulation of macronutrients in the above ground part, with the exception of sulfur. The accumulation of Cu, Mn and Zn micronutrients were higher in plants treated with Cu, Mn and Zn phosphites, respectively. The green color index was influenced by the treatments after pathogen inoculation, with the highest values for Zn and Cu phosphites. Before inoculation, the products influenced net CO₂ assimilation rate (A), stomatal conductance (g_s) and internal CO₂ concentration (C_i). The parameters g_s and C_i increased, which indicates that the treatments can physiologically benefit the plants in the absence of a stress condition. After fungal inoculation, the Cu, Mn and Zn phosphites caused positive physiological effects, leading to the highest A values and adequate carboxylation efficiency (CE), which increases the capacity of plants to assimilate CO₂. These phosphites also maintained adequate water use efficiency and g_s and C_i values. Such indexes corresponded to lower disease severity, indicating that Mn, Zn and Cu phosphites reduced the stress caused by the disease, preserving the functionality of the photosynthetic apparatus.

     

Soybean drought-stressed plants impair Anticarsia gemmatalis (Lepidoptera: Erebidae) midgut proteolytic activity and survival

Phytoparasitica - Soybean plants are exposed to multiple stresses during development. Co-occurring stresses can activate common defense pathways on plants, increasing end products concentrations,...     

Standard area diagram set for assessment of severity and temporal progress of apple blotch

Apple blotch (Marssonina coronaria) is a foliar disease of increasing importance globally. Methods to quantify the disease and knowledge about epidemiology are required for new studies on the disease. The objectives of this study were to develop a standard area diagram set (SADs) to assess apple blotch severity and to describe the temporal progress of the disease under field conditions on older and younger leaves of two apple cultivars. For the development of SADs, symptomatic leaves were collected and scanned to obtain the actual severity. Based on the pattern of the disease, a SADs was elaborated and validated. Leaf severities were estimated without and with SADs by 12 raters to validate the tool. After validation, the SADs was used to assess apple blotch in older and younger leaves of selected shoots during the vegetative cycle of cvs. Eva and Gala. SADs severities ranged from 0.2 to 96%. Accuracy, precision, and reliability of the estimates were significantly improved when the SADs was used. In the field, the onset of apple blotch was in late spring and greater increases in severity occurred during summer. Rates of disease progress ranged from 0.09 to 0.13. Epidemics were different in older and younger leaves at the end of the apple vegetative cycle for both cultivars tested. Our work provided a tool for apple blotch quantification and described the disease progress curve under subtropical conditions, which can contribute as basis for future studies.