Glomerella leaf spot in apple: validation of proposed diagrammatic scale and efficiency of fungicides

A diagrammatic scale to assess Glomerella leaf spot severity (Colletotrichum spp) was developed and validated during the tryout of a fungicide efficiency experiment in the field. Apple leaves were collected for determination of minimum and maximum severity limits; intermediate levels were obtained according to "Weber-Fechner's stimulus-response law". Scale validation was performed by four raters, which estimated the severity in 100 leaves; with and without the use of the scale. An experiment was carried out in a commercial orchard in randomized blocks with 10 plants. The treatments and dosages (g 100 L-1 of water) used were: cyprodinil (15); pyrimethanil (30, 37.5, 45); propineb (140) e mancozeb (160) + tebuconazole (12.50), and a control (no spray). The incidence and severity in leaves; number of fruits, weight and incidence in fruit (harvest) and defoliation (after harvest) were evaluated. The proposed scale showed the levels of 0.08; 0.28; 0.99; 3.45; 11.23 and 30.93%. The scale was adequate for severity assessment; R2 changed from 0.68 to 0.96 with the use of the scale. Pyrimethanil treatments did not control the disease. The incidence on fruit was 30 and on leaves 63%. The incidence was reduced in 35.6% (propineb) and 33.7% (mancozeb + tebuconazole) related to the control, these treatments were efficient to control the disease. The defoliation was 44 % in the control against 9.6 and 2.5% to propineb and mancozeb + tebuconazole.

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Diagrammatic scale for assessment of soybean rust severity

Fitopatologia Brasileira ◽

10.1590/s0100-41582006000100011 ◽

2006 ◽

Vol 31 (1) ◽

pp. 63-68 ◽

Cited By ~ 110

Author(s):

Cláudia V. Godoy ◽

Lucimara J. Koga ◽

Marcelo G. Canteri

Keyword(s):

Glycine Max ◽

Scale Validation ◽

Soybean Rust ◽

Phakopsora Pachyrhizi ◽

Stimulus Response ◽

Accuracy And Precision ◽

Rust Severity ◽

Severity Levels ◽

Diagrammatic Scale

A diagrammatic scale to assess soybean (Glycine max) rust severity, caused by the fungus Phakopsora pachyrhizi, was developed in this study. Leaflets showing different severity levels were collected for determination of the minimum and maximum severity limits; intermediate levels were determined according to "Weber-Fechner's stimulus-response law". The proposed scale showed the levels of 0.6; 2; 7; 18; 42, and 78.5%. Scale validation was performed by eight raters (four inexperienced and four experienced), who estimated the severity of 44 soybean leaflets showing rust symptoms, with and without the use of the scale. Except for rater number eight, all showed a tendency to overestimate severity without the aid of the diagrammatic scale. With the scale, the raters obtained better accuracy and precision levels, although the tendency to overestimate was maintained. Experienced raters were more accurate and precise than inexperienced raters, and assessment improvements with the use of the scale were more significant for inexperienced raters.

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Differentiation of Isolates of Glomerella cingulata and Colletotrichum spp. Associated with Glomerella Leaf Spot and Bitter Rot of Apples Using Growth Rate, Response to Temperature, and Benomyl Sensitivity

Plant Health Progress ◽

10.1094/php-2005-0719-01-rs ◽

2005 ◽

Vol 6 (1) ◽

pp. 6 ◽

Cited By ~ 1

Author(s):

Eugenia González ◽

Turner B. Sutton

Keyword(s):

Growth Rate ◽

Leaf Spot ◽

Molecular Diversity ◽

Colletotrichum Gloeosporioides ◽

Glomerella Cingulata ◽

Optimum Growth Temperature ◽

Bitter Rot ◽

Colletotrichum Spp ◽

Glomerella Leaf Spot ◽

Response To Temperature

Cultural characteristics were investigated as a way to distinguish isolates of Glomerella cingulata and Colletotrichum spp. associated with Glomerella leaf spot and bitter rot of apples from those that cause only bitter rot. The growth rate, response to temperature, and benomyl sensitivity of 27 isolates of Glomerella cingulata, 12 isolates of Colletotrichum gloeosporioides, and 7 isolates of C. acutatum, collected from apple orchards located in the U.S. and Brazil and previously characterized based on morphology, vegetative compatibility, and mitochondrial DNA (mtDNA) haplotypes, were determined. These isolates represent the genetic and molecular diversity within isolates of C. gloeosporioides, C. acutatum, and G. cingulata from apples found in a previous study. Slower growth, lower optimum growth temperature, and less sensitivity to benomyl distinguished isolates of C. acutatum from isolates of G. cingulata and C. gloeosporioides. However, growth rate and benomyl sensitivity were not useful for distinguishing between G. cingulata and C. gloeosporioides or differentiating isolates of G. cingulata that cause leaf spot and bitter rot from those that only cause bitter rot. Accepted for publication 17 May 2005. Published 19 July 2005.

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Improving accuracy, precision and reliability of severity estimates of Glomerella leaf spot on apple leaves using a new standard area diagram set

European Journal of Plant Pathology ◽

10.1007/s10658-018-01610-0 ◽

2018 ◽

Vol 153 (3) ◽

pp. 975-982 ◽

Cited By ~ 4

Author(s):

Rafaele Regina Moreira ◽

Henrique da Silva Silveira Duarte ◽

Louise Larissa May De Mio

Keyword(s):

Leaf Spot ◽

Apple Leaves ◽

Glomerella Leaf Spot ◽

Improving Accuracy

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Population Diversity within Isolates of Colletotrichum spp. Causing Glomerella Leaf Spot and Bitter Rot of Apples in Three Orchards in North Carolina

Plant Disease ◽

10.1094/pdis.2004.88.12.1335 ◽

2004 ◽

Vol 88 (12) ◽

pp. 1335-1340 ◽

Cited By ~ 14

Author(s):

Eugenia González ◽

Turner B. Sutton

Keyword(s):

North Carolina ◽

Leaf Spot ◽

Morphological Characters ◽

Population Diversity ◽

Colletotrichum Acutatum ◽

Vegetative Compatibility Groups ◽

Bitter Rot ◽

Lincoln County ◽

Colletotrichum Spp ◽

Glomerella Leaf Spot

The population diversity within isolates of Glomerella cingulata and Colletotrichum spp. associated with Glomerella leaf spot and bitter rot of apples was studied in an orchard of cv. Granny Smith located in Wilkes County, NC, and one orchard each of cultivars Granny Smith and Gala located in Lincoln County, NC. Morphological characters and vegetative compatibility groups (VCGs) were used to determine diversity within the species. The relative frequencies of the morphological types found within each species in each orchard were also determined. G. cingulata was the predominant species associated with bitter rot in the three orchards and Glomerella leaf spot in the Gala orchard. In the three orchards, different morphological types were observed within isolates of G. cingulata and Colletotrichum acutatum, but not within isolates of Colletotrichum gloeosporioides. Isolates of C. gloeosporioides were not found in the orchard of cv. Granny Smith in Lincoln County. In the other two orchards, C. gloeosporioides represented the lowest proportion of the population. Three VCGs were found among isolates of G. cingulata (VCG-1, 2, and 6), two among isolates of C. gloeosporioides (VCG-9 and 10), and two among isolates of C. acutatum (VCG-15 and 16). VCGs 2, 6, 9, 10, 15, and 16 were found in the Granny Smith orchard in Wilkes County, VCGs 1, 2, and 6 in the Gala orchard in Lincoln County, and VCGs 2 and 6 in the Granny Smith orchard in Lincoln County. Differences in frequencies among the different morphological types found within the three orchards remained relatively similar throughout the season and from year to year, suggesting that the relative frequencies of G. cingulata, C. gloeosporioides, and C. acutatum remain stable in an orchard once the fungi are established.

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Effects of Temperature, Wetness Duration, and Moisture on the Conidial Germination, Infection, and Disease Incubation Period of Glomerella cingulata

Plant Disease ◽

10.1094/pdis-04-14-0361-re ◽

2015 ◽

Vol 99 (2) ◽

pp. 249-256 ◽

Cited By ~ 20

Author(s):

Bing Wang ◽

Bao-Hua Li ◽

Xiang-Li Dong ◽

Cai-Xia Wang ◽

Zhen-Fang Zhang

Keyword(s):

Incubation Period ◽

Leaf Spot ◽

Logistic Models ◽

Conidial Germination ◽

Effective Control ◽

Conidial Suspension ◽

Glomerella Cingulata ◽

Apple Leaves ◽

Effects Of Temperature ◽

Glomerella Leaf Spot

Glomerella leaf spot (GLS) caused by Glomerella cingulata is a newly emergent disease that results in severe defoliation and fruit spots. Currently, GLS is not effectively controlled in China due to a lack of understanding of its epidemiology. Therefore, the effects of temperature, wetness duration, and moisture on conidial germination, infection, and the disease incubation period of GLS were examined by inoculating cv. Gala apple leaves with a conidial suspension and performing in vitro germination assays. Conidia could germinate and form appressoria at temperatures ranging from 5 to 35°C, with an optimum temperature of 27.6°C. The germination of conidia required free water or a nearly saturated relative humidity, with only a few conidia germinating and forming appressoria when the RH was less than 99%. The conidial germination dynamics at 10, 25, and 30°C were well represented by three logistic models. The infection of cv. Gala apple leaves by conidia occurred at temperatures ranging from 15 to 35°C. The minimum wetness duration required for infection by conidia at different temperatures was described using a polynomial equation, and the lowest minimum wetness duration was 2.76 h, which occurred at 27.6°C according to the polynomial. Successful infection by conidia was represented by the number of lesions per leaf, which increased with extended wetness durations at the conidial infection stage for six tested temperatures, with the exception of 10°C, when the minimum wetness durations were satisfied. The associations of successfully infected conidia with wetness duration at temperatures of 15, 20, 25, and 30°C were described by four logistic models. Conidia infections developed into visible lesions at temperatures ranging from 15 to 30°C, and the shortest incubation period of 2 days was observed at 25°C. These data and models can be used to construct forecasting models and develop effective control systems for Glomerella leaf spot.

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The promotion of thiophanate-methyl and tebuconazole for the continuous control of Glomerella leaf spot in apple leaves by adding pellouxite as a synergistic reagent

Journal of Plant Diseases and Protection ◽

10.1007/s41348-017-0102-z ◽

2017 ◽

Vol 124 (6) ◽

pp. 631-639

Author(s):

Yuran Wang ◽

Pingliang Li ◽

Hongye Zhen ◽

Baohua Li

Keyword(s):

Leaf Spot ◽

Continuous Control ◽

Thiophanate Methyl ◽

Apple Leaves ◽

Glomerella Leaf Spot

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ITS-rDNA phylogeny of Colletotrichum spp. causal agent of apple Glomerella leaf spot

Ciência Rural ◽

10.1590/s0103-84782010005000051 ◽

2010 ◽

Vol 40 (4) ◽

pp. 806-812 ◽

Cited By ~ 8

Author(s):

Diorvania Ribeiro Giaretta ◽

Amauri Bogo ◽

Cileide Maria Medeiros Coelho ◽

Altamir Frederico Guidolin ◽

Adriana Cibele de Mesquita Dantas ◽

...

Keyword(s):

Leaf Spot ◽

Restriction Enzymes ◽

Causal Agent ◽

Divergent Evolution ◽

Paulo State ◽

Pineapple Guava ◽

Apple Production ◽

Citrus Orchards ◽

Colletotrichum Spp ◽

Glomerella Leaf Spot

Several diseases have affected apple production, among them there is Glomerella leaf spot (GLS) caused by Colletotrichum spp. The first report of this disease in apple was in plants nearby citrus orchards in São Paulo State, Brazil. The origin of this disease is still not clear, and studies based on the molecular phylogeny could relate the organisms evolutionarily and characterize possible mechanisms of divergent evolution. The amplification of 5.8S-ITS (Internal Transcribed Spacer) of rDNA of 51 pathogenic Colletotrichum spp. isolates from apples, pineapple guava and citrus produced one fragment of approximately 600 bases pairs (bp) for all the isolates analyzed. The amplified fragments were cleaved with restriction enzymes, and fragments from 90 to 500bp were obtained. The sequencing of this region allowed the generation of a phylogenetic tree, regardless of their hosts, and 5 isolated groups were obtained. From the "in silico" comparison, it was possible to verify a variation from 93 to 100% of similarity between the sequences studied and the Genbank data base. The causal agent of GLS is nearly related (clustered) to isolates of pineapple guava and to the citrus isolates used as control.

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