scholarly journals Weather During Critical Epidemiological Periods and Subsequent Severity of Powdery Mildew on Grape Berries

Plant Disease ◽  
2016 ◽  
Vol 100 (1) ◽  
pp. 116-124 ◽  
Author(s):  
Michelle M. Moyer ◽  
David M. Gadoury ◽  
Wayne F. Wilcox ◽  
Robert C. Seem
Keyword(s):  
Powdery Mildew ◽  
Disease Severity ◽  
Late Summer ◽  
Environmental Variable ◽  
Collective Effects ◽  
Risk Models ◽  
Current Season ◽  
Grape Berries ◽  
Effects Of Temperature ◽  
Recursive Partition

Recorded severity of grape powdery mildew on berries of untreated, susceptible hybrid cultivars varied from 0.2 to 50.5% across a 30-year period in Geneva, NY; within 7 of those years, cluster disease severity ranged from 3.42 to 99.5% on Vitis vinifera ‘Chardonnay’. Although existing temperature-driven risk models could not account for this annual variation, pan evaporation (Epan), an environmental variable influenced by the collective effects of temperature, vapor pressure deficit, solar radiation, and wind speed, did. Logistic regression analysis (LRA) was used to classify epidemics as either mild or severe. Recursive partition analysis (RPA) provided a simplified decision tree for calculation of powdery mildew risk and incorporated (i) an estimate of the relative primary inoculum levels based on temperatures in the previous late summer and (ii) the current season favorability for pathogen development during the grapevine phenological period critical for berry infection by Erysiphe necator. Although the LRA had fewer instances of misclassification, RPA provided a rapid means for seasonal risk classification. Both the RPA and LRA models are able to describe disease severity risk in real time or can be used to forecast risk, thereby allowing growers to adjust management programs in a responsive manner.

Influence of sowing dates on the incidence of powdery mildew of chilli

2017 ◽  
Vol 4 (2) ◽  
Author(s):  
SUDHEENDRA A. ASHTAPUTRE
Keyword(s):  
Powdery Mildew ◽  
Field Experiment ◽  
Disease Severity ◽  
Agricultural Research ◽  
Time Interval ◽  
Research Station ◽  
Inoculum Potential ◽  
Weather Factors ◽  
Agricultural Research Station ◽  
Sowing Dates

A field experiment was conducted during kharif, 2005 at Agricultural Research station, Devihosur, Haveri, Karnataka to assess the progress of powdery mildew at different time interval of sowing dates. Totally 20 different dates of sowings were imposed in the experiment at an interval of 10 days. The crop sown on last week of May to mid of June recorded minimum disease severity compared to rest of the date of sowings. This clearly indicated that crop sown during this period suffers less, which may be due to low inoculum potential, whereas late sown crop suffers more because of the readily available inoculum in the early sown crops. Low disease severity in last week of May to mid of June sowing may be attributed to the non-congenial weather factors for the development of the disease.

scholarly journals Variety resistance of winter barley to powdery mildew in the field in 1976−2005

2008 ◽  
Vol 43 (No. 3) ◽  
pp. 87-96 ◽  
Author(s):  
A. Dreiseitl
Keyword(s):  
Powdery Mildew ◽  
Disease Severity ◽  
Powdery Mildew Resistance ◽  
Specific Resistance ◽  
Winter Barley ◽  
Mildew Resistance ◽  
Average Resistance ◽  
The Difference ◽  
The Given ◽  
Resistance Of Varieties

The results of evaluation of powdery mildew resistance in winter barley varieties in 285 Czech Official Trials conducted at 20 locations were analysed. Over the period, the number of varieties tested per year increased from four to seven in 1976−1985 to 53−61 in 2002−2005. To assess the resistance of varieties, only trials with sufficient disease severity were used. In 1976−2000, six varieties (1.7% of the varieties tested in the given years) ranked among resistant (average resistance of a variety in a year > 7.5) including NR-468 possessing the gene <i>Mla13</i>, KM-2099 with <i>mlo</i> and Marinka with the genes <i>Mla7</i>, <i>MlaMu2</i>. In 2001−2005, already 33 varieties (16.9%) ranked among resistant, of which Traminer possessing the genes <i>Ml(St)</i> and <i>Ml(IM9 </i> dominated. The proportion of susceptible varieties (average resistance ≤ 5.5) did not change in the two mentioned periods. Two-rowed varieties began to be tested as late as in 1990 (the first variety was Danilo), however, no difference was found in the resistance of two- and six-rowed varieties. Using an example of two pairs of varieties (Dura-Miraj and Marinka-Tiffany) with identical genes for specific resistance but with different resistance in the field, the efficiency of non-specific resistance is discussed. The resistance of domestic and foreign varieties was similar in 1994−2000; however, in 2001−2005 the difference was 0.75 point to disadvantage of domestic ones.

scholarly journals Continuous Lighting Reduces Conidial Production and Germinability in the Rose Powdery Mildew Pathosystem

Plant Disease ◽  
2010 ◽  
Vol 94 (3) ◽  
pp. 339-344 ◽  
Author(s):  
A. Suthaparan ◽  
Arne Stensvand ◽  
S. Torre ◽  
Maria L. Herrero ◽  
R. I. Pettersen ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Disease Severity ◽  
Interspecific Hybrid ◽  
Day Length ◽  
Artificial Light ◽  
Potted Plants ◽  
Severity Of Disease ◽  
Detached Leaves ◽  
Growth Chambers ◽  
The Rose

The effect of day length on production and germinability of conidia and severity of disease caused by Podosphaera pannosa, the causal agent of rose powdery mildew, was studied. Whole potted plants or detached leaves of Rosa interspecific hybrid ‘Mistral’ were inoculated with P. pannosa and exposed to 0, 12, 18, 20, 22, or 24 h of artificial light per day in growth chambers equipped with mercury lamps. Increasing duration of illumination from 18 to 20 to 24 h per day reduced production of conidia by 22 to 62%. Exposure to 24 h of illumination per day also strongly reduced disease severity compared with 18 h. Our results suggest that increasing day lengths from 18 h per day to 20 to 24 h may suppress the disease significantly and, thereby, reduce the need for fungicide applications against powdery mildew.

Identification of powdery mildew (Erysiphe graminis sp. tritici) and take-all disease (Gaeumannomyces graminis sp. tritici) in wheat (Triticum aestivum L.) by means of leaf reflectance measurements

2006 ◽  
Vol 1 (2) ◽  
pp. 275-288 ◽  
Author(s):  
Simone Graeff ◽  
Johanna Link ◽  
Wilhelm Claupein
Keyword(s):  
Powdery Mildew ◽  
Disease Severity ◽  
Near Infrared ◽  
Plant Stress ◽  
Stress Factors ◽  
Gaeumannomyces Graminis ◽  
Disease Assessment ◽  
Leaf Reflectance ◽  
Reflectance Measurements ◽  
Take All

AbstractThe ability to identify diseases in an early infection stage and to accurately quantify the severity of infection is crucial in plant disease assessment and management. A greenhouse study was conducted to assess changes in leaf spectral reflectance of wheat plants during infection by powdery mildew and take-all disease to evaluate leaf reflectance measurements as a tool to identify and quantify disease severity and to discriminate between different diseases. Wheat plants were inoculated under controlled conditions in different intensities either with powdery mildew or take-all. Leaf reflectance was measured with a digital imager (Leica S1 Pro, Leica, Germany) under controlled light conditions in various wavelength ranges covering the visible and the near-infrared spectra (380–1300 nm). Leaf scans were evaluated by means of L*a*b*-color system. Visual estimates of disease severity were made for each of the epidemics daily from the onset of visible symptoms to maximum disease severity. Reflectance within the ranges of 490780 nm (r2 = 0.69), 510780nm (r2 = 0.74), 5161300nm (r2 = 0.62) and 5401300 nm (r2 = 0.60) exhibited the strongest relationship with infection levels of both powdery mildew and take-all disease. Among the evaluated spectra the range of 490780nm showed most sensitive response to damage caused by powdery mildew and take-all infestation. The results of this study indicated that disease detection and discrimination by means of reflectance measurements may be realized by the use of specific wavelength ranges. Further studies have to be carried out, to discriminate powdery mildew and take-all infection from other plant stress factors in order to develop suitable decision support systems for site-specific fungicide application.

scholarly journals Host Barriers and Responses to Uncinula necator in Developing Grape Berries

2004 ◽  
Vol 94 (5) ◽  
pp. 438-445 ◽  
Author(s):  
Andrea Ficke ◽  
David M. Gadoury ◽  
Robert C. Seem ◽  
Dale Godfrey ◽  
Ian B. Dry
Keyword(s):  
Cell Wall ◽  
Powdery Mildew ◽  
Wall Thickness ◽  
Infection Process ◽  
Cell Wall Thickness ◽  
Antifungal Compound ◽  
Uncinula Necator ◽  
Grape Berries ◽  
Pathogenesis Related ◽  
Cuticle Thickness

Grape berries are highly susceptible to powdery mildew 1 week after bloom but acquire ontogenic resistance 2 to 3 weeks later. We recently demonstrated that germinating conidia of the grape powdery mildew pathogen (Uncinula necator) cease development before penetration of the cuticle on older resistant berries. The mechanism that halts U. necator at that particular stage was not known. Several previous studies investigated potential host barriers or cell responses to powdery mildew in berries and leaves, but none included observation of the direct effect of these factors on pathogen development. We found that cuticle thickness increased with berry age, but that ingress by the pathogen halted before formation of a visible penetration pore. Cell wall thickness remained unchanged over the first 4 weeks after bloom, the time during which berries progressed from highly susceptible to nearly immune. Autofluorescent polyphenolic compounds accumulated at a higher frequency beneath appressoria on highly susceptible berries than on highly resistant berries; and oxidation of the above phenolics, indicated by cell discoloration, developed at a significantly higher frequency on susceptible berries. Beneath the first-formed appressoria of all germinated conidia, papillae occurred at a significantly higher frequency on 2- to 5-day-old berries than on 30- to 31-day-old fruit. The relatively few papillae observed on older berries were, in most cases (82.8 to 97.3%), found beneath appressoria of conidia that had failed to produce secondary hyphae. This contrasted with the more abundantly produced papillae on younger berries, where only 35.4 to 41.0% were located beneath appressoria of conidia that had failed to produce secondary hyphae. A pathogenesis-related gene (VvPR-1) was much more highly induced in susceptible berries than in resistant berries after inoculation with U. necator. In contrast, a germin-like protein (VvGLP3) was expressed within 16 h of inoculation in resistant, but not in susceptible berries. Our results suggest that several putative barriers to infection, i.e., cuticle and cell wall thickness, antimicrobial phenolics, and two previously described pathogenesis-related proteins, are not principal causes in halting pathogen ingress on ontogenically resistant berries, but rather that infection is halted by one or more of the following: (i) a preformed physical or biochemical barrier near the cuticle surface, or (ii) the rapid synthesis of an antifungal compound in older berries during the first few hours of the infection process.

scholarly journals Effects of temperature and sand on E. coli survival in a northern lake water microcosm

2006 ◽  
Vol 4 (3) ◽  
pp. 389-393 ◽  
Author(s):  
Reyneé W. Sampson ◽  
Sarah A. Swiatnicki ◽  
Vicki L. Osinga ◽  
Jamie L. Supita ◽  
Colleen M. McDermott ◽  
...  
Keyword(s):  
Lake Water ◽  
Late Summer ◽  
Most Probable Number ◽  
Recreational Waters ◽  
New Host ◽  
Probable Number ◽  
E Coli ◽  
Enzyme Substrate ◽  
Public Health Officials ◽  
Effects Of Temperature

A concern for public health officials is the presence of Escherichia coli (E. coli), an indicator of fecal contamination, in monitoring recreational waters. While E. coli is unlikely to cause disease in humans, its presence may indicate other more pathogenic microorganisms. Many factors can lead to changes in the survival of E. coli outside of the animal intestine and may affect the probability of colonizing a new host. Survival of bacteria in recreational water has been linked to water temperature, and most recently to the presence of sand on the beach. This project looked at the survival of an environmental E. coli isolate in lake water. Lake water microcosms were placed at 4, 10, 14, or 25°C for up to 36 d and an enzyme-substrate test (Colisure®, IDEXX Corp.) was used to determine the most probable number (MPN) of E. coli/100 ml water. E. coli numbers at all temperatures declined over the duration of the experiment. The decline was most pronounced at 14°C and was slowest at 4°C. The presence of sand in the microcosm increased the time that E. coli survived, regardless of temperature. From a beach management standpoint, these findings indicate that E. coli may persist in the environment in cooler water longer than in the warmer water encountered in late summer.

scholarly journals Detecting Wheat Powdery Mildew and Predicting Grain Yield Using Unmanned Aerial Photography

Plant Disease ◽  
2018 ◽  
Vol 102 (10) ◽  
pp. 1981-1988 ◽  
Author(s):  
Wei Liu ◽  
Xueren Cao ◽  
Jieru Fan ◽  
Zhenhua Wang ◽  
Zhengyuan Yan ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Grain Yield ◽  
Disease Severity ◽  
Flight Altitude ◽  
Imaging Data ◽  
Remote Imaging ◽  
Wheat Powdery Mildew ◽  
Imaging Tool ◽  
Random Coefficient Regression ◽  
Relationship Of

High-resolution aerial imaging with an unmanned aerial vehicle (UAV) was used to quantify wheat powdery mildew and estimate grain yield. Aerial digital images were acquired at Feekes growth stage (GS) 10.5.4 from flight altitudes of 200, 300, and 400 m during the 2009–10 and 2010–11 seasons; and 50, 100, 200, and 300 m during the 2011–12, 2012–13, and 2013–14 seasons. The image parameter lgR was consistently correlated positively with wheat powdery mildew severity and negatively with wheat grain yield for all combinations of flight altitude and year. Fitting the data with random coefficient regression models showed that the exact relationship of lgR with disease severity and grain yield varied considerably from year to year and to a lesser extent with flight altitude within the same year. The present results raise an important question about the consistency of using remote imaging information to estimate disease severity and grain yield. Further research is needed to understand the nature of interyear variability in the relationship of remote imaging data with disease or grain yield. Only then can we determine how the remote imaging tool can be used in commercial agriculture.

Microsphaera penicillata. [Descriptions of Fungi and Bacteria].

1968 ◽  
Author(s):  
K. G. Mukerji
Keyword(s):  
North America ◽  
Powdery Mildew ◽  
Geographical Distribution ◽  
World Wide ◽  
Late Summer ◽  
Erysiphe Pisi ◽  
Temperature And Humidity ◽  
Young Leaves ◽  
Dry Seasons

Abstract A description is provided for Microsphaera penicillata. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On species of Alnus, Betula, Syringa, Lathyrus, sweet peas and numerous other hosts (Saknon, 1900; Stevens, 1925; 39: 739; 41: 175) DISEASES: Powdery mildew of alder and lilac. Forms a white to grey floury appearance on the surface of broad leaves of many hard wood trees. It is more prevalent on sweet peas than Erysiphe pisi (CMI Descript. 155) in North America in spring when temperature and humidity are fluctuating. The foliage may be malformed, dropping prematurely or drying out and shrivelling. It is also prevalent on lilac in late summer and autumn, sometimes in dry seasons almost completely covering the foliage, but generally too late in the season to cause serious damage. Young leaves are more susceptible. GEOGRAPHICAL DISTRIBUTION: World-wide on alder and lilac and occasionally occurring on numerous other hosts. Distributed generally in North America and Europe, also reported from Chile, China, India and Japan (Salmon, 1900, 39: 739; 41: 175). TRANSMISSION: Spores wind borne.

scholarly journals Novel Source of Biotic Stress Resistance Identified from Brassica Species and its Wild Relatives

Proceedings ◽  
2020 ◽  
Vol 36 (1) ◽  
pp. 195
Author(s):  
Rashmi Yadav ◽  
J. Nanjundan ◽  
Ashish K. Gupta ◽  
Mahesh Rao ◽  
Jameel Akhtar ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Disease Severity ◽  
Insect Pests ◽  
Indian Mustard ◽  
Wild Relatives ◽  
Lepidium Sativum ◽  
Sclerotinia Stem Rot ◽  
Sources Of Resistance ◽  
Alternaria Blight ◽  
White Rust

In rapeseed and mustard, the major diseases (downy mildew, white rust, Alternaria blight and Sclerotinia stem rot) cause 37–47%loss in pod formation and 17–54% reduction in grain yield. The identification of new sources of resistance is a high priority in breeding programs. About 3000 germplasm accessions of Indian mustard were evaluated under multiple environments (3 seasons) at hot spots (4 locations) and under artificial epiphytophic conditions against insect pests and diseases (aphids, white rust, powdery mildew and Alternaria blight). Accessions IC265495, IC313380, EC766091, EC766133, EC766134, EC766192, EC766230, EC766272 were identified as highly resistant to white rust (A. candida) with disease severity reaction (Percent disease severity Index, PDI = 0) under artificial inoculation. Accession RDV 29 showed the inheritance of resistant source for powdery mildew in Indian mustard. Screening of brassica wild relatives (about 25 species) for white rust found that Brassica fruticulosa, Brassica tournefortii, Camelina sativa, Diplotaxis assurgens, D. catholica, D. cretacia, D. Erucoides, D. Muralis, Lepidium sativum had highly resistance (PDI = 0) to Delhi isolates of white rust. Several traits identified from cultivated and related species will be useful for genetic improvement of rapeseed and mustard.

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