Disease Severity Of Powdery Mildew Research Articles

Evaluation of germicidal UV-C light for suppression of grape powdery mildew and Botrytis bunch rot in Western Oregon.

Germicidal ultraviolet light (UV-C) has been shown to effectively suppress several plant pathogens, as well as some arthropod pests. Recent reports describe the efficacy of nighttime applications of UV-C at doses from 100 to 200 J/m2 in vineyards to reduce grape powdery mildew (Erysiphe necator). Our in vitro studies confirmed efficacy of UV-C to inhibit germination of E. necator and Botrytis cinerea conidia, demonstrated a range of tolerances to UV-C within a collection of E. necator isolates, and showed growth stage-specific effects of UV-C on B. cinerea. Nighttime use of UV-C was evaluated at 48 to 96 J/m2 in small plot trials (<1,000 vines) from 2020 to 2023. Once or twice weekly UV-C applications significantly reduced the incidence of foliar powdery mildew compared to non-UV-C-treated controls (P < 0.02). Suppression of powdery mildew on fruit was less consistent, where once or twice weekly UV-C exposure reduced powdery mildew disease severity in 2020 (P = 0.04), 2021 (P = 0.02) and 2023 (P =0.003), but less so in 2022 (P = 0.07). Bunch rot severity was not significantly reduced with UV-C treatment in any year of the study. Application of UV-C until the onset of fruit color change (veraison) also had a minimal effect on the fruit soluble solids, pH, anthocyanins, or phenolics in harvested fruit at any UV-C dose or frequency (P > 0.10). Suppression of powdery mildew by nighttime application UV-C at lower doses in small plots suggests that such treatments merit further evaluation in larger-scale studies in Western Oregon.

Genetic Mapping, Identification, and Characterization of a Candidate Susceptibility Gene for Powdery Mildew in Cannabis sativa.

Powdery mildew (PM) in Cannabis sativa is most frequently caused by the biotrophic fungus Golovinomyces ambrosiae. Based on previously characterized variation in susceptibility to PM, biparental populations were developed by crossing the most resistant cultivar evaluated, 'FL 58', with a susceptible cultivar, 'TJ's CBD'. F1 progeny were evaluated and displayed a range of susceptibility, and two were self-pollinated to generate two F2 populations. In 2021, the F2 populations (n = 706) were inoculated with PM and surveyed for disease severity. In both F2 populations, 25% of the progeny were resistant, while the remaining 75% showed a range of susceptibility. The F2 populations, as well as selected F1 progeny and the parents, were genotyped with a single-nucleotide polymorphism array, and a consensus genetic map was produced. A major effect quantitative trait locus on C. sativa chromosome 1 (Chr01) and other smaller-effect quantitative trait loci (QTL) on four other chromosomes were identified. The most associated marker on Chr01 was located near CsMLO1, a candidate susceptibility gene. Genomic DNA and cDNA sequencing of CsMLO1 revealed a 6.8-kb insertion in FL 58, relative to TJ's CBD, of which 846 bp are typically spliced into the mRNA transcript encoding a premature stop codon. Molecular marker assays were developed using CsMLO1 sequences to distinguish PM-resistant and PM-susceptible genotypes. These data support the hypothesis that a mutated MLO susceptibility gene confers resistance to PM in C. sativa and provides new genetic resources to develop resistant cultivars. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Enhancing chili pepper (Capsicum annuum L.) resistance and yield against powdery mildew (Leveillula taurica) with beneficial bacteria

BackgroundLeveillula taurica is an obligate pathogen that causes powdery mildew on chili pepper (Capsicum annuum L.) which is considered one of the most serious diseases for the crop.ResultsLeveillula taurica was isolated from infected pepper plants in Assiut Governorate, Egypt. Pathogenicity test was performed, and it was found that the pathogen can cause the symptoms of powdery mildew on the pepper plant. Under greenhouse conditions, treatment with Bacillus thuringiensis MW740161.1, Pseudomonas fluorescens, and Bacillus subtilis cultures resulted in a significant reduction in conidial germination of the pathogen (69.07, 29.55, and 19.58%, respectively). Spraying chili pepper plants with the microorganisms effectively reduced the powdery mildew's disease severity. Also, treatment with the bacterial strains resulted in a significant (P 0.05%) increase in the yield of chili pepper. Based on the findings, it appears that the use of B. thuringiensis, as foliar spraying, significantly induced resistance of chili pepper plants against L. taurica and stimulated many biochemical functions in the plant. Also, it increased the crop yield compared to all other treatments.ConclusionsThis study recommends B. thuringiensis as a viable alternative to harmful pesticides, and it is feasible to formulate an appropriate fungicide for the sustainable green production of chili peppers. The B. thuringiensis can increase the resistance of chili pepper plant to L. taurica the causal pathogen of powdery mildew.

Evaluation of Native Bacterial Isolates for Control of Cucumber Powdery Mildew under Greenhouse Conditions

Cucumber plants are often attacked by various pathogens, which can considerably decrease production and cause significant losses. One of the most prevalent fungal diseases is powdery mildew, caused by an obligate pathogen, Podosphaera xanthii. It is a serious disease that causes significant damage to the whole plant, i.e., leaves, fruits, and stems, under both greenhouse and field conditions. The main objective of this result is to assess the effectiveness of Bacillus spp. against cucumber powdery mildew under in vitro and in vivo conditions. Treatment with B. licheniformis and B. aerius culture filtrates reduced the conidial germination of the pathogen by 60 and 85%, respectively. Under greenhouse conditions, spraying cucumber plants with both microorganisms was effective at reducing powdery mildew disease severity. High reductions of disease severity were achieved by treatment of B. licheniformis as a cell suspension and B. aerius strain as culture filtrate, 45.3 and 77.3%, respectively, two days before inoculation. Additionally, treatment with these bacterial strains resulted in a significant increase in the fresh and dry weights of the cucumber plants. The highest increase of fresh and dry weight was found with B. licheniformis CS and B. aerius strain CF treatment at two days before or after infection. After treatment with the bioagents, the content of total phenols, polyphenol oxidase, and peroxidase was enhanced in treatment plants. The use of B. licheniformis and B. aerius as foliar sprays significantly induced resistance to P. xanthii in cucumber plants and stimulated many biochemical functions. Therefore, we propose B. licheniformis and B. aerius as an effective alternative to harmful chemicals.

Management of powdery mildew and aphid in organically grown Indian mustard (Brassica juncea L.) through different oils

All the cultivated Brassica species exhibited powdery mildew severity with highest (43.2%) on Brassica juncea followed by B. rapa (28.0%) which is widely cultivated in India. Yield losses from 10-90 per cent with reduction in 6.47 per cent oil content have been estimated from different Brassica species. Hence, the present study was carried out to evaluate different oils to manage powdery mildew disease and aphids in an organically grown mustard crop. Five oils (castor, groundnut, sunflower, neem and mustard oil) and ghee were evaluated against powdery mildew (Erysiphae cruciferarum) and aphid (Lipaphis erysimi) of Indian mustard (Brassica juncea). Castor oil 50 EC, neem oil 50 EC and mustard oil 50 EC and deshi ghee 50 EC (@ 100 ml/10 litre water) were effective over untreated control in reducing powdery mildew disease severity when applied as foliar spray (@ 5 ml/litre) in the experiment carried out in organic field (plot No. B-2 at Agronomy Instruction Farm, S. D. Agricultural University, Sardarkrushinagar). Maximum reduction in germinated conidia (66.0%) over control, disease severity (50.0%), area under disease progress curve (AUDPC) values (51.8%) and maximum increase over control in 1000 seed weight (16.7%) and seed yield (10.3%) was observed with neem oil. This was followed by the application of ghee which exhibited reduced disease severity (22.9%) and AUDPC values (30.6%) and increased seed yield (8.1%) and the application of castor oil 50 EC which exhibited an increased in seed yield (8.0%) and reduced powdery mildew severity (20.8%). Shortest log phase was observed with neem oil during 10th std. week. All the oils tested (castor, groundnut, sunflower, neem and mustard oil) and deshi ghee were effective in reducing aphid population (39.5 to 65.9%) and damage index (6.1 to 25.1%). A maximum reduction in aphid population (65.9%) over control and lowest aphid damage index (3.70) was observed with neem oil 50 EC 6 days after 2nd spray. Application of neem oil, castor oil and deshi ghee resulted in increased seed yield (8.1 to 10.4%). This information could be useful in devising strategies for powdery mildew and aphid management in organic cultivation, eco-friendly management and IPM of mustard.

Hyperspectral Monitoring of Powdery Mildew Disease Severity in Wheat Based on Machine Learning.

Powdery mildew has a negative impact on wheat growth and restricts yield formation. Therefore, accurate monitoring of the disease is of great significance for the prevention and control of powdery mildew to protect world food security. The canopy spectral reflectance was obtained using a ground feature hyperspectrometer during the flowering and filling periods of wheat, and then the Savitzky–Golay method was used to smooth the measured spectral data, and as original reflectivity (OR). Firstly, the OR was spectrally transformed using the mean centralization (MC), multivariate scattering correction (MSC), and standard normal variate transform (SNV) methods. Secondly, the feature bands of above four transformed spectral data were extracted through a combination of the Competitive Adaptive Reweighted Sampling (CARS) and Successive Projections Algorithm (SPA) algorithms. Finally, partial least square regression (PLSR), support vector regression (SVR), and random forest regression (RFR) were used to construct an optimal monitoring model for wheat powdery mildew disease index (mean disease index, mDI). The results showed that after Pearson correlation, two-band optimization combinations and machine learning method modeling comparisons, the comprehensive performance of the MC spectrum data was the best, and it was a better method for pretreating disease spectrum data. The transformed spectral data combined with the CARS–SPA algorithm was able to extract the characteristic bands more effectively. The number of bands screened was more than the number of bands extracted by the OR data, and the band positions were more evenly distributed. In comparison of different machine learning modeling methods, the RFR model performed the best (coefficient of determination, R2 = 0.741–0.852), while the SVR and PLSR models performed similarly (R2 = 0.733–0.836). Taken together, the estimation accuracy of spectral data transformation using the MC method combined with the RFR model (MC-RFR) was the highest, the model R2 was 0.849–0.852, and the root mean square error (RMSE) and the mean absolute error (MAE) ranged from 2.084 to 2.177 and 1.684 to 1.777, respectively. Compared with the OR combined with the RFR model (OR-RFR), the R2 increased by 14.39%, and the R2 of RMSE and MAE decreased by 23.9 and 27.87%. Also, the monitoring accuracy of flowering stage is better than that of grain filling stage, which is due to the relative stability of canopy structure in flowering stage. It can be seen that without changing the shape of the spectral curve, and that the use of MC to preprocess spectral data, the use of CARS and SPA algorithms to extract characteristic bands, and the use of RFR modeling methods to enhance the synergy between multiple variables, and the established model (MC-CARS-SPA-RFR) can better extract the covariant relationship between the canopy spectrum and the disease, thereby improving the monitoring accuracy of wheat powdery mildew. The research results of this study provide ideas and methods for realizing high-precision remote sensing monitoring of crop disease status.

Integration of bioagents with antioxidants to control Powdery Mildew disease in sunflower

Powdery mildew disease, caused by Erysiphe cichoracearum, is considered one of the most severe pathogenic threats of sunflower worldwide. This study discusses how to improve the effect of biocontrol agents, as a more economic and eco-friendlier alternative to fungicides, by mixing different bioagents (Trichoderma harzianum and Bacillus subtilis) with different antioxidants (ascorbic acid and salicylic acid), either individually or combined. They were applied to sunflower during two successive seasons to determine their effectiveness in promoting growth and inducing resistance in sunflower against powdery mildew disease under field conditions. Results show that all treatments reduced the severity of powdery mildew disease significantly compared with control. A synergistic effect was noticed when combining T. harzianum and salicylic acid led to a significant decrease in powdery mildew disease severity in sunflower in comparison to control. In general, the results suggested that the integration of antioxidants with bioagents showed a better response to control powdery mildew disease than single treatments. In field experiments, the applied treatments significantly increased all of the studied growth parameters, plant length, fresh and dry weight. All treatments showed a remarkable increase in physiological aspects (enzymes activity and total phenol content).

Management of Powdery Mildew on Ninebark Using Sanitizers, Biorational Products, and Fungicides

Ninebark (Physocarpus opulifolius) is a popular ornamental shrub and considered a hardy and tough plant that can thrive in different environmental conditions and resist diseases. However, powdery mildew, caused by Podosphaera physocarpi, can severelyaffect ninebark, deteriorating the ornamental value and making them unmarketable. Only a few studies have been done in managing powdery mildew of ninebark. The current study focuses on evaluating and identifying effective products (sanitizers, biorational products, and fungicides) for the management of powdery mildew disease of ninebark. A total of 12 treatments, including nontreated control, were studied. The experiment was arranged in randomized complete block design with four-single ‘Mindia Coppertina®’ ninebark plant per treatment and repeated twice. Powdery mildew disease severity, growth parameters, and phytotoxicity were assessed in the study. All treatments significantly reduced the powdery mildew disease severity and disease progress [area under disease progress curve (AUDPC)] compared with the nontreated control. The treatments, such as azoxystrobin + benzovindiflupyr at 0.17 and 0.23 g·L–1 total active ingredients (a.i.) applied, chlorothalonil + propiconazole at 1.12 mL·L–1 total a.i. applied, azoxystrobin + tebuconazole at 0.11 and 0.16 g·L–1 total a.i. applied, and giant knotweed extract [Reynoutria sachalinensis (0.5 mL·L–1 total a.i. applied)] were the most effective treatments in reducing disease severity and disease progress in both trials. The treatments had no significant effects on the plant growth parameters such as height and width. In Expt. 2, azoxystrobin + benzovindiflupyr and hydrogen peroxide + peroxyacetic acid treated plants showed the low level of phytotoxic symptoms. The phytotoxicity of these two treatments in Expt. 2 could be related to higher environmental temperature during the experimental period.

Surfactants in plant disease management: A brief review and case studies

AbstractIn plant disease management, surfactants are generally used in combination with pesticides to facilitate delivery of the pesticide chemicals to the target sites in plants, vectors, or pathogens. Their intended use is rarely for direct effect on plant pathogens. However, trends in recent studies have revealed an appreciable increase in their use for direct management of plant diseases. In this paper, we briefly review the progress made in the use of surfactants for disease management, as adjuvants and when applied for direct effect. We carried out experiments to evaluate the effect of selected synthetic surfactants (Cohere, Kinetic, Silwet‐77, and Induce) on powdery mildew in squash and bacterial spot in tomato. Results from this study showed that the effect of surfactants on these pathogens is dependent on the type of plant pathogen or disease. All tested surfactants exhibited in vitro bactericidal activity against Xanthomonas perforans, a causal pathogen of bacterial spot of tomato. In the greenhouse, Cohere significantly reduced disease severity of powdery mildew in squash compared to the untreated control. Cohere also showed promise in field trials against bacterial spot of tomato, but the other surfactants tested promoted this disease. Our studies demonstrate the importance of evaluating surfactants for their use in management of plant diseases both for direct effect and as adjuvants in tank mix.

Genetics of Quality Attributes and Powdery Mildew Severity in Garden Pea (Pisum sativum Var. Hortense L.) under Sub Temperate Conditions of North-Western Himalayas

Background: The choice of appropriate breeding method for improvement of traits depends largely on gene action. Hence, an understanding of the inheritance of quantitative traits is essential to develop an efficient breeding strategy.Methods: Twelve generations of three inter-varietal crosses involving four diverse parents of garden pea were studied for biochemical traits and powdery mildew disease severity to analyze the nature of gene effects by using generation mean anaylsis.Result: Duplicate type of epistasis was observed for protein content in all or one or other crosses. In most cases, the presences of linkage among interacting genes or higher order interactions at several loci were involved. Non-fixable gene effects were many times higher than fixable one in all the crosses indicating a major role non-additive gene effects in the inheritance of these traits. The type of gene effects along with presence of non-allelic interactions suggested the adoption of population improvement methods to break undesirable linkages through recombination. The other alternative can be to defer selection in the later generations by advancing segregating populations through bulk pedigree or SSD methods with one or two inter-matings like recurrent selection. Based on pod characteristics and powdery mildew disease severity203 single plant progenies were isolated over the generations of three crosses along with bulk seed following SSD and bulk method to isolate transgressive segregants.

Management Powdery Mildew of Marigold (Calendula Officinalis) Using some Nanoparticles and Chitosan

The effect of seven substances, Copper, CuO, ZnO, AlO NPs (8 mg L−1), CuO, ZnO, AlO (8 mg L−1) and chitosan was evaluated under both greenhouse and field conditions during two growing seasons (2017/2018 and 2018/2019) to control powdery mildew disease caused by Erysiphe cichoracearum on marigold (Calendula officinalis). Results have shown that all the treatments tested had decreased disease severity compared to the non-treated control. In this respect, chitosan showed the best effect in decreasing disease severity followed by ZnO NPs. Meanwhile, CuO gave the lowest effect in this respect. The decrease in disease severity of powdery mildew was positively expressed by an increase in crop parameters, i.e. numbers of inflorescence weight, fresh and dry weights of plants, plant height, number of branches and increased chlorophyll ( a and b) and carotenoids.

Assortment for host resistance and eco-friendly management of mulberry powdery mildew caused by Phyllactinia corylea (Pers.) Karst

Powdery mildew caused by Phyllactinia corylea (Pers.) Karst, is an obligate parasitic disease of mulberry inflicting considerable qualitative as well as quantitative losses of leaf yield. Screening of 16 mulberry varieties against powdery mildew disease under field conditions yielded two resistant varieties with the lower powdery mildew disease severity of 2.5 and 5.42 per cent in a variety S-13 and in variety S-34 had 3 and 5.37 per cent after 55 and 70 days after planting respectively. The three varieties viz., Kanva-2 / M-5, Mysore local and S-1635 were moderately resistant with the less DS values of 11.43, 11.47 and 11.48 per cent respectively. In management studies, the plant extracts at all concentrations tested were effective in suppressing the disease and at higher concentration of 15%, Zinger officinale reduced the disease to 60.31 per cent and Lantana camara to 59.04 per cent disease over control and were considered as best for managing powdery mildew disease in mulberry. Among the culture filtrate of different bioagents tested, the Trichoderma harzianum reduced the disease to 51.56 per cent and Pseudomonas fluorescens to 51.09 per cent over control at 15% concentration and were shown to be potent in fading away the disease.

Molecular mapping of two quantitative trait loci for adult-plant resistance to powdery mildew in common wheat (Triticum aestivum L.)

Powdery mildew is one of the major wheat diseases in regions with maritime or semi-continental climate and can strongly affect grain yield. Breeding wheat varieties with quantitative resistance to powdery mildew would be relatively more durable and promising than varieties with only major resistance genes (Pm genes). The chief aim of the present study is to map the quantitative trait loci (QTLs) for adult plant resistance (APR) to powdery mildew. A population of 176 recombinant inbred lines was developed from a cross of “Shannong 0431 × Lumai 21” (SN0431 × LM21) and evaluated for disease severity of powdery mildew under two cropping seasons. Two major QTLs (QPm.sdau-2A and QPm.sdau-2B) for APR to powdery mildew were mapped on chromosomes 2A and 2B, which were contributed by LM21 and SN0431. The molecular markers associated with the QTLs will be useful for selecting partial and potentially durable resistance genes against powdery mildew.

Identification of powdery mildew resistance QTL in strawberry (Fragaria\u2009\xd7\u2009ananassa)

Key MessagePowdery mildew resistance in two strawberry mapping populations is controlled by both stable and transient novel QTL of moderate effect. Some low transferability of QTL across wider germplasm was observed.The obligate biotrophic fungus Podosphaera aphanis is the causative agent of powdery mildew on cultivated strawberry (Fragaria × ananassa). Genotypes from two bi-parental mapping populations ‘Emily’ × ‘Fenella’ and ‘Redgauntlet’ × ‘Hapil’ were phenotyped for powdery mildew disease severity in a series of field trials. Here, we report multiple QTL associated with resistance to powdery mildew, identified in ten phenotyping events conducted across different years and locations. Six QTL show a level of stable resistance across multiple phenotyping events; however, many other QTL were represented in a single phenotyping event and therefore must be considered transient. Subsequent screening of identified QTL across a validation set determined whether identified QTL remained closely linked to the associated resistance gene in the wider germplasm. Furthermore, a preliminary association analysis identified a novel conserved locus for further investigation. Our data suggest that resistance is highly complex and that multiple, primarily additive, sources of quantitative resistance to powdery mildew exist across strawberry germplasm. Utilisation of the reported markers in marker-assisted breeding or genomic selection would lead to improved powdery mildew-resistant strawberry cultivars, particularly where the studied parents, progeny and close pedigree material are included in breeding germplasm.

Gas Chromatography-Mass Spectrometry (GC-MS) Analysis of Sugar Beet Leaf Extracts in Response to Exogenous Application of Resistance Inducers to Manage Sugar Beet Powdery Mildew

The effect of foliar application of some chemical resistance inducers i.e., chitosan, ascorbic acid, salicylic acid and tap water as a control were tested to evaluate their efficacy to induce systemic resistance against Erysiphe betae, the causal agent of sugar beet powdery mildew (Herkl cv.) versus the traditional fungicide Opera under greenhouse and field conditions at Gemmeiza Agric. Res. Sta., Agric. Res. Cent. (ARC), Egypt during two successive winter seasons (2014/2015 and 2015/2016). Under greenhouse conditions, results revealed that spraying plants with all the tested IRCs reduced the disease severity of powdery mildew. The fungicide Opera was the most effective treatment in reducing disease severity and increasing the efficacy followed by chitosan and salicylic acid. Also, all treatments significantly increased total phenols and orthodihydric (OD) phenol content of the leaves compared to the control at 15, 30 and 45 days after inoculation. The GC-MS analysis of methanol extracts of 60 days old leaves of sugar beet plants under the greenhouse conditions, which have been treated with chitosan, ascorbic acid, salicylic acid as inducers to the systemic resistance of sugar beet against Erysiphe betae recorded the highest concentration (peak area %) for all bioactive phytochemical compounds such as flavonoids, alcohols, aldehydes, aromatic compounds, fatty acid methyl esters, terpenoids, phenolics and steroids that can be postulated for antimicrobial activity compared to control (tap water). Under field conditions, results indicated that the fungicide Opera was the most effective treatment for controlling powdery mildew followed by ascorbic acid. Meanwhile, all treatments showed lower effect than the fungicide Opera in this regard but higher than control. All treatments increased root yield per feddan compared to the control. The fungicide Opera and salicylic acid gave the highest root yield per feddan followed by ascorbic acid then chitosan. Moreover, salicylic acid and the fungicide Opera gave the highest percentages of total soluble solids (T.S.S.) and sucrose percentages, whereas salicylic acid, ascorbic acid and fungicide Opera gave the highest percentages of purity in sugar beet roots.

Pumpkin powdery mildew disease severity influences the fungal diversity of the phyllosphere.

Phyllosphere microbiota play a crucial role in plant-environment interactions and their microbial community and function are influenced by biotic and abiotic factors. However, there is little research on how pathogens affect the microbial community of phyllosphere fungi. In this study, we collected 16 pumpkin (Cucurbita moschata) leaf samples which exhibited powdery mildew disease, with a severity ranging from L1 (least severe) to L4 (most severe). The fungal community structure and diversity was examined by Illumina MiSeq sequencing of the internal transcribed spacer (ITS) region of ribosomal RNA genes. The results showed that the fungal communities were dominated by members of the Basidiomycota and Ascomycota. The Podosphaera was the most dominant genus on these infected leaves, which was the key pathogen responsible for the pumpkin powdery mildew. The abundance of Ascomycota and Podosphaera increased as disease severity increased from L1 to L4, and was significantly higher at disease severity L4 (P < 0.05). The richness and diversity of the fungal community increased from L1 to L2, and then declined from L2 to L4, likely due to the biotic pressure (i.e., symbiotic and competitive stresses among microbial species) at disease severity L4. Our results could give new perspectives on the changes of the leaf microbiome at different pumpkin powdery mildew disease severity.

Induction of Defense-Related Physiological and Antioxidant Enzyme Response against Powdery Mildew Disease in Okra (Abelmoschus esculentus L.) Plant by Using Chitosan and Potassium Salts

Foliar sprays of three plant resistance inducers, including chitosan (CH), potassium sorbate (PS) (C6H7kO2), and potassium bicarbonates (PB) (KHCO3), were used for resistance inducing against Erysiphe cichoracearum DC (powdery mildew) infecting okra plants. Experiments under green house and field conditions showed that, the powdery mildew disease severity was significantly reduced with all tested treatments of CH, PS, and PB in comparison with untreated control. CH at 0.5% and 0.75% (w/v) plus PS at 1.0% and 2.0% and/or PB at 2.0% or 3.0% recorded as the most effective treatments. Moreover, the highest values of vegetative studies and yield were observed with such treatments. CH and potassium salts treatments reflected many compounds of defense singles which leading to the activation power defense system in okra plant. The highest records of reduction in powdery mildew were accompanied with increasing in total phenolic, protein content and increased the activity of polyphenol oxidase, peroxidase, chitinase, and β-1,3-glucanase in okra plants. Meanwhile, single treatments of CH, PS, and PB at high concentration (0.75%, 2.0%, and/or 3.0%) caused considerable effects. Therefore, application of CH and potassium salts as natural and chemical inducers by foliar methods can be used to control of powdery mildew disease at early stages of growth and led to a maximum fruit yield in okra plants.

Role of some Non-traditional Compounds in Managing Sugar Beet Powdery Mildew

Certain non-traditional compounds such as compost tea, humic acid and sulphated canola oil were tested as foliar application to evaluate their efficacy to induce systemic resistance against Erysiphe betae, the causal agent of powdery mildew in sugar beet (Herkl cv.) versus the traditional fungicide Opera under greenhouse and field conditions at Gemmeiza Agricultural Research Station, Agricultural Research Center (A.R.C.), Egypt during two successive winter seasons (2014/2015 and 2015/2016). Under greenhouse conditions, results revealed that spraying plants with all the tested compounds reduced disease severity of powdery mildew. The fungicide Opera was the most effective treatment in reducing disease severity and increasing the efficacy followed by Sulplex, compost tea and humic acid. Also, all treatments significantly increased total phenols and orthodihydric (OD) phenol content of the leaves compared to the control 15, 30 and 45 days after inoculation. Also, spraying plants with the tested compounds increased the activity of peroxidase (PO), polyphenoloxidase (PPO) and chitinase enzymes compared to the control, 15, 30 and 45 days after artificial inoculation. Inthe detection of chitinase activity by using SDS-glycol chitin polyacrylamide gel electrophoresis the molecular weight for all samples ranged from 28 to 30 kDa. high intensity band expressing the highest chitinase activity was found in compost-tea treatment followed by Sulplex. Moreover, control, fungicide Opera and humic acid treatments showed low chitinase activity. Under field experiments, results indicated that the fungicide Opera was the most effective treatment for controlling powdery mildew followed by Sulplex and compost tea. Meanwhile, humic acid was the lowest effective one in this regard. All treatments increased root yield per feddan compared to the control. The fungicide Opera and Sulplex gave the highest root yield per feddan followed by compost tea then humic acid. Moreover, compost tea and Sulplex gave the highest percentages of total soluble solids (T.S.S.), sucrose percentages in beet roots and purity.

Comparative Study of Powdery Mildew (Erysiphe polygoni) Disease Severity and Its Effect on Yield and Yield Components of Field Pea (Pisum sativum L.) in the Southeastern Oromia, Ethiopia

Field pea or “dry pea” (Pisum sativum L.) is an annual cool-season food legume which grows worldwide and is the major pulse crop in the highlands of Bale next to Faba bean. The experiment was conducted for two consecutive cropping seasons; 2011/12 and 2012/13 at Sinana agricultural research center (SARC) on-station research site. The objective was to find out the effect of Powdery mildew disease on field pea yield and yield components. Local field pea cultivar was used with a fungicide Benomyl at a rate of 2.5 kg/ha and four fungicide application schemes (spraying every 7 days, 14 days, 21 days and no fungicide spray) arranged in randomized complete block design (RCBD) with 3 replications. Logistic model (ln [y/ (1-y)]) was employed to analyze the Field experiment data using SAS procedure. The association between disease parameters and yield and yield components were assessed using regression and correlation techniques. ANOVA has shown significant difference (p ≤ 0.05) among treatments for disease severity. The highest diseases severity (41.98%) and Area Under Disease Progress Curve (AUDPC) (1458.33% days) and the lowest disease severity (13.89%) and AUDPC (471.15% days) were recorded from a plot with no fungicide treatment and plot sprayed every 7 days, respectively. Similarly, the highest disease progress rate (r) (0.044227 units-day-1) and the lowest r (-0.006122 units-day-1) were recorded from a plot with no fungicide treatment and plot sprayed every 7 days, respectively. Regarding the yield and yield related parameters; ANOVA has shown significant variations (P ≤ 0.05) between treatments for number of pods per plant, seeds per plant, TKW and grain yield. The highest number of pod per plant (21.75), seed per plant (89.5), TKW (189.81 g) and grain yield (2945.6 kg/ha) were recorded from plots sprayed every 7 days; while the lowest were from non-sprayed plots. On the other hand, the higher grain yield loss of 21.09% and the lowest loss (8.53%) were recorded from plots without fungicide spray and plot received spray at 7 days interval, respectively. The linear regression between powdery mildew severity index and grain yield revealed significant difference (P ≤ 0.0001) between treatments; and the estimated slope of the regression line obtained for Powdery mildew severity index was -34.16. Correlation analysis has shown that Powdery mildew disease severity have significantly strong negative correlation with grain yield (r= -0.76120, P ≤ 0.01). Similarly, grain yield has significant strong negative correlation (r= -0.76298, P ≤ 0.0001) with AUDPC.

Effect of some Plant Extracts on Sugar Beet Powdery Mildew

This work was carried out under field conditions of two Governorates i.e. Menoufiya and Giza, during two successive sugar beet growing seasons (2013/14 and 2014/15). The efficacy of using extracts of four medicinal and aromatic plants, i.e. Fennel, Rosemary, Marjoram and Thyme extract by three organic solvents (ethanol, petroleum ether and chloroform) on the disease severity of sugar beet powdery mildew was studied. All treatments significantly reduced the disease severity of powdery mildew disease. Rosemary ethanol extract was the best treatment in reducing disease severity in the both seasons at the two governorate followed by fennal ethanol extract. On the other hand, marjoram petroleum ether extract was the least effective one. Also, the application of these treatments increased some crop parameters, i.e. total soluble solids (T.S.S), sucrose percent in root, purity of sugar and root weight.