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Lavern W. Timmer - One of the best experts on this subject based on the ideXlab platform.
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Saprophytic Colonization of Citrus Twigs by Diaporthe Citri and Factors Affecting Pycnidial Production and Conidial Survival.
Plant disease, 2007Co-Authors: S. N. Mondal, Antonio Vicent, R. F. Reis, Lavern W. TimmerAbstract:ABSTRACT Melanose, caused by Diaporthe Citri, produces reddish brown lesions on the fruit, leaves, and twigs of citrus trees, and greatly reduces the marketability of fresh fruit. Most of the inoculum is produced in pycnidia on dead twigs in the tree canopy, which exude large numbers of conidia in slimy masses. In this study, detached twigs inoculated with conidia were readily colonized and produced large numbers of pycnidia within 30 to 40 days when they were soaked 3 to 4 h on alternate days. Conidial production was measured by wetting twigs in a rain tower periodically and collecting the conidia in the runoff water. Production began after 80 days and continued for nearly 300 days. In other experiments, production of mature pycnidia on detached twigs was greatest at 94 to 100% relative humidity (RH) and at 28°C. Low RH and temperature, however, favored survival of conidia in exuded masses on twigs. In the field, colonization of detached twigs by D. Citri was high in rainy season, moderate in spring and ...
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Efficacy of Pre- and Postinoculation Application of Fungicides to Expanding Young Citrus Leaves for Control of Melanose, Scab, and Alternaria Brown Spot.
Plant disease, 2007Co-Authors: S. N. Mondal, Antonio Vicent, R. F. Reis, Lavern W. TimmerAbstract:ABSTRACT In greenhouse trials, copper hydroxide, pyraclostrobin, and famoxadone were applied to actively growing young citrus seedlings to determine the duration of protection of young leaves provided by these fungicides against melanose, caused by Diaporthe Citri, citrus scab, caused by Elsinoe fawcettii, and Alternaria brown spot, caused by Alternaria alternata. Fungicides were applied to different sets of potted plants of grapefruit for control of melanose, of rough lemon for control of scab, and of Dancy tangerine for control of Alternaria brown spot 1 to 6 days prior to inoculation, as well as on the day of inoculation. Leaf area of treated shoots was estimated on the day of fungicide application and the day of inoculation and disease severity evaluated subsequently. In most cases, copper hydroxide and famoxadone provided at least 50% control of all three diseases for only about 2 days after application. Generally, there was little or no disease control when the products were applied 4 or more days b...
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Baseline Sensitivities of Fungal Pathogens of Fruit and Foliage of Citrus to Azoxystrobin, Pyraclostrobin, and Fenbuconazole.
Plant disease, 2005Co-Authors: S. N. Mondal, Alka Bhatia, Turksen Shilts, Lavern W. TimmerAbstract:ABSTRACT The baseline sensitivities for mycelial growth of foliar fungal pathogens of citrus, Colletotrichum acutatum, Alternaria alternata, Elsinoe fawcettii, Diaporthe Citri, and Mycosphaerella Citri, the causal agents of postbloom fruit drop, brown spot of tangerine, citrus scab, melanose, and greasy spot, respectively, were determined in vitro for azoxystrobin, pyraclostrobin, and fenbuconazole. The effective dose to reduce growth by 50% (ED50 values) was determined for each pathogen-fungicide combination using five isolates from different citrus areas of Florida and eight fungicide concentrations. A discriminatory dose for each combination was selected near the ED50, and the range of sensitivity of 50 to 62 isolates of each fungal species was determined. The effect of salicylhydroxamic acid (SHAM) on the sensitivity of the five fungal species to azoxystrobin and pyraclostrobin was determined. Since mycelial growth of A. alternata was insensitive to azoxystrobin, the effect of that fungicide with and ...
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Factors affecting pycnidium production of Diaporthe Citri on detached citrus twigs
Plant disease, 2004Co-Authors: S. N. Mondal, J. P. Agostini, L. Zhang, Lavern W. TimmerAbstract:Melanose, caused by Diaporthe Citri, produces black-to-reddish brown lesions on twigs, leaves, and fruit of citrus and reduces the external quality of fruit destined for the fresh market. Inoculum for infection is produced primarily in pycnidia formed on dead twigs, and conidia are dispersed by rainwater. In laboratory studies, the effect of moisture, temperature, twig size, and melanose severity on pycnidium production on detached twigs was investigated. Pycnidium production was greatest when twigs were soaked for 3 to 4 h on alternate days three times per week and the temperature was 28°C. Production was greatest on twigs 3 to 5 mm in diameter and less on thinner or thicker twigs. Pycnidium production was related linearly to melanose severity on the twigs, and almost no pycnidia were produced on asymptomatic twigs. In the field, pycnidium production was greatest on detached, melanose-affected twigs placed in the canopy monthly during January to April than it was on twigs placed in the canopy during other months. The largest number of pycnidia was produced from May to August when fruit is most susceptible. The number of pycnidia produced was related significantly to degree-days above 20°C and weakly related to cumulative rainfall. Knowledge of inoculum production peaks may assist in timing of pruning and fungicide sprays.
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Greenhouse Evaluation of Products That Induce Host Resistance for Control of Scab, Melanose, and Alternaria Brown Spot of Citrus
Plant disease, 2003Co-Authors: J. P. Agostini, P. M. Bushong, Lavern W. TimmerAbstract:ABSTRACT Products that induce disease resistance in plants were evaluated on potted seedlings of rough lemon for citrus scab, caused by Elsinoe fawcettii; grapefruit for melanose, caused by Diaporthe Citri; and Dancy tangerine for Alternaria brown spot caused by Alternaria alternata pv. Citri. Plants were pruned to a single stem with mature leaves and treated at bud break or various times thereafter. New foliage was inoculated and subsequently evaluated for disease severity. Oxycom, Nutriphite, Messenger, Goemar H11, Serenade, ReZist, ProPhyt, Aliette, Actigard, and KeyPlex were evaluated and compared with benomyl or strobilurin fungicides as standards. Most products reduced disease severity compared with the untreated control, but were less effective than standard fungicides. The most generally effective products were ReZist and Actigard, those that contain or produce phosphorous acid (Aliette and Nutriphite), and a bacterial preparation (Serenade). Oxycom and Messenger controlled scab well in some tests...
Kevin D. Hyde - One of the best experts on this subject based on the ideXlab platform.
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Endophytic Diaporthe associated with Citrus: A phylogenetic reassessment with seven new species from China
Fungal biology, 2015Co-Authors: Feng Huang, Xin Hou, Dhanushka Udayanga, Xinghong Wang, Xiufeng Mei, Kevin D. HydeAbstract:Phytopathogenic species of Diaporthe are associated with melanose, stem-end rot and gummosis diseases of Citrus. However, little is known about the occurrence of species of Diaporthe as endophytes and saprobes. In this study, we obtained 58 strains of Diaporthe, including 44 endophytic isolates from cultivated Citrus in China. The nuclear ribosomal internal transcribed spacer (ITS), partial sequences of translation elongation factor 1-α (EF1-α), beta-tubulin (TUB), and histone-3 (HIS) gene regions were analysed to determine the species of the isolates collected. In combined analysis of four gene regions, these strains grouped in 16 distinct clades in Diaporthe. The isolates were identified in Diaporthe arecae species complex, Diaporthe Citri, Diaporthe Citriasiana, Diaporthe Citrichinensis, Diaporthe endophytica, Diaporthe eres, Diaporthe hongkongensis, and Diaporthe sojae based on molecular phylogeny and morphology. Seven new species are described from Citrus namely, Diaporthe biconispora, Diaporthe biguttulata, Diaporthe discoidispora, Diaporthe multigutullata, Diaporthe ovalispora, Diaporthe subclavata, and Diaporthe unshiuensis with descriptions and illustrations.
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Species limits in Diaporthe: molecular re-assessment of D. Citri, D. cytosporella, D. foeniculina and D. rudis
Persoonia, 2014Co-Authors: Dhanushka Udayanga, Lisa A. Castlebury, Amy Y. Rossman, Kevin D. HydeAbstract:Species of Diaporthe are important plant pathogens of a wide range of hosts worldwide. In the present study the species causing melanose and stem end rot diseases of Citrus spp. are revised. Three species of Diaporthe occurring on Citrus are characterised, including D. Citri, D. cytosporella and D. foeniculina. Morphology and phylogenetic analyses of the complete nuclear ribosomal internal transcribed spacer regions and partial sequences of actin, beta-tubulin, calmodulin and translation elongation factor 1-α were used to resolve species on Citrus and related Diaporthe species. Diaporthe Citri occurs on Citrus throughout the Citrus-growing regions of the world. Diaporthe cytosporella is found on Citrus in Europe and California (USA). Diaporthe foeniculina, including the synonym D. neotheicola, is recognised as a species with an extensive host range including Citrus. Diaporthe medusaea, a name widely used for D. Citri, was determined to be a synonym of D. rudis, a species with a broad host range. Diaporthe Citri is delimited based on molecular phylogenetic analysis with the inclusion of the conserved ex-type and additional collections from different geographic locations worldwide. Diaporthe cytosporella, D. foeniculina and D. rudis are epitypified, fully described and illustrated with a review of all synonyms based on molecular data and morphological studies. Newly designed primers are introduced to optimise the amplification and sequencing of calmodulin and actin genes in Diaporthe. A discussion is provided of the utility of genes and the need for multi-gene phylogenies when distinguishing species of Diaporthe or describing new species.
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(2141) Proposal to conserve the name Phomopsis Citri H. S. Fawc. ( Diaporthe Citri ), with a conserved type, against Phomopsis Citri (Sacc.) Traverso & Spessa ( Ascomycota : Diaporthales : Diaporthaceae )
Taxon, 2013Co-Authors: Amy Y. Rossman, Lisa A. Castlebury, Dhanushka Udayanga, Kevin D. HydeAbstract:(2141) Phomopsis Citri H.S. Fawc. in Phytopathology 2: 109. Jun 1912, nom. cons. prop. Typus: United States, Florida, Lake Alfred, Ana, “On twigs of Citrus sp.”, 26 Apr 2000, Timmer (BPI No. 892456 [dried culture of AR 3405]), typ. cons. prop. (H) Phomopsis Citri (Sacc.) Traverso & Spessa in Bol. Soc. Brot. 25: 123. 1910 (Phoma Citri Sacc. in Nuovo Giorn. Bot. Ital. 8: 200. Aug 1876). Lectotypus (hic designatus): Italy, Treviso, a Vittorio, “on branch of Citrus limon”, “Diplodia Citri”, Oct 1875, Saccardo in Mycotheca Veneto No. 332 (FH).
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Diaporthe species occurring on citrus in China
Fungal Diversity, 2013Co-Authors: Feng Huang, Xin Hou, Megan M. Dewdney, Guoqing Chen, Kevin D. HydeAbstract:Diaporthe species are important pathogens of a wide range of hosts including many economically important crops. Diaporthe Citri is generally accepted to cause melanose of Citrus fruits, leaves and shoots; stem-end rot of fruits and gummosis of perennial branches. In this study, 147 strains of Diaporthe were isolated from diseased leaves, twigs, fruits and branches of Citrus from Shaanxi, Zhejiang, Guangxi, Fujian, Guangdong, Jiangxi, Hunan, Chongqing and Shanghai and identified by morphology and molecular analysis of nuclear ribosomal internal transcribed spacer (ITS), partial sequences of translation elongation factor 1-α (EF 1-α), tubulin (TUB) and calmodulin (CAL) genes. All strains from Citrus clustered in three clades. Diaporthe Citri was the predominant species and is compared with strains from Florida, USA, where this species was first collected and described. Two new taxa differing from D. Citri are described as D. Citriasiana and D. Citrichinensis in this paper. Inoculation tests indicate that all three species are able to cause stem-end rot of fruits, while only D. Citri could cause melanose on leaves.
S. N. Mondal - One of the best experts on this subject based on the ideXlab platform.
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Saprophytic Colonization of Citrus Twigs by Diaporthe Citri and Factors Affecting Pycnidial Production and Conidial Survival.
Plant disease, 2007Co-Authors: S. N. Mondal, Antonio Vicent, R. F. Reis, Lavern W. TimmerAbstract:ABSTRACT Melanose, caused by Diaporthe Citri, produces reddish brown lesions on the fruit, leaves, and twigs of citrus trees, and greatly reduces the marketability of fresh fruit. Most of the inoculum is produced in pycnidia on dead twigs in the tree canopy, which exude large numbers of conidia in slimy masses. In this study, detached twigs inoculated with conidia were readily colonized and produced large numbers of pycnidia within 30 to 40 days when they were soaked 3 to 4 h on alternate days. Conidial production was measured by wetting twigs in a rain tower periodically and collecting the conidia in the runoff water. Production began after 80 days and continued for nearly 300 days. In other experiments, production of mature pycnidia on detached twigs was greatest at 94 to 100% relative humidity (RH) and at 28°C. Low RH and temperature, however, favored survival of conidia in exuded masses on twigs. In the field, colonization of detached twigs by D. Citri was high in rainy season, moderate in spring and ...
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Efficacy of Pre- and Postinoculation Application of Fungicides to Expanding Young Citrus Leaves for Control of Melanose, Scab, and Alternaria Brown Spot.
Plant disease, 2007Co-Authors: S. N. Mondal, Antonio Vicent, R. F. Reis, Lavern W. TimmerAbstract:ABSTRACT In greenhouse trials, copper hydroxide, pyraclostrobin, and famoxadone were applied to actively growing young citrus seedlings to determine the duration of protection of young leaves provided by these fungicides against melanose, caused by Diaporthe Citri, citrus scab, caused by Elsinoe fawcettii, and Alternaria brown spot, caused by Alternaria alternata. Fungicides were applied to different sets of potted plants of grapefruit for control of melanose, of rough lemon for control of scab, and of Dancy tangerine for control of Alternaria brown spot 1 to 6 days prior to inoculation, as well as on the day of inoculation. Leaf area of treated shoots was estimated on the day of fungicide application and the day of inoculation and disease severity evaluated subsequently. In most cases, copper hydroxide and famoxadone provided at least 50% control of all three diseases for only about 2 days after application. Generally, there was little or no disease control when the products were applied 4 or more days b...
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Baseline Sensitivities of Fungal Pathogens of Fruit and Foliage of Citrus to Azoxystrobin, Pyraclostrobin, and Fenbuconazole.
Plant disease, 2005Co-Authors: S. N. Mondal, Alka Bhatia, Turksen Shilts, Lavern W. TimmerAbstract:ABSTRACT The baseline sensitivities for mycelial growth of foliar fungal pathogens of citrus, Colletotrichum acutatum, Alternaria alternata, Elsinoe fawcettii, Diaporthe Citri, and Mycosphaerella Citri, the causal agents of postbloom fruit drop, brown spot of tangerine, citrus scab, melanose, and greasy spot, respectively, were determined in vitro for azoxystrobin, pyraclostrobin, and fenbuconazole. The effective dose to reduce growth by 50% (ED50 values) was determined for each pathogen-fungicide combination using five isolates from different citrus areas of Florida and eight fungicide concentrations. A discriminatory dose for each combination was selected near the ED50, and the range of sensitivity of 50 to 62 isolates of each fungal species was determined. The effect of salicylhydroxamic acid (SHAM) on the sensitivity of the five fungal species to azoxystrobin and pyraclostrobin was determined. Since mycelial growth of A. alternata was insensitive to azoxystrobin, the effect of that fungicide with and ...
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Factors affecting pycnidium production of Diaporthe Citri on detached citrus twigs
Plant disease, 2004Co-Authors: S. N. Mondal, J. P. Agostini, L. Zhang, Lavern W. TimmerAbstract:Melanose, caused by Diaporthe Citri, produces black-to-reddish brown lesions on twigs, leaves, and fruit of citrus and reduces the external quality of fruit destined for the fresh market. Inoculum for infection is produced primarily in pycnidia formed on dead twigs, and conidia are dispersed by rainwater. In laboratory studies, the effect of moisture, temperature, twig size, and melanose severity on pycnidium production on detached twigs was investigated. Pycnidium production was greatest when twigs were soaked for 3 to 4 h on alternate days three times per week and the temperature was 28°C. Production was greatest on twigs 3 to 5 mm in diameter and less on thinner or thicker twigs. Pycnidium production was related linearly to melanose severity on the twigs, and almost no pycnidia were produced on asymptomatic twigs. In the field, pycnidium production was greatest on detached, melanose-affected twigs placed in the canopy monthly during January to April than it was on twigs placed in the canopy during other months. The largest number of pycnidia was produced from May to August when fruit is most susceptible. The number of pycnidia produced was related significantly to degree-days above 20°C and weakly related to cumulative rainfall. Knowledge of inoculum production peaks may assist in timing of pruning and fungicide sprays.
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Fungal Diseases of Fruit and Foliage of Citrus Trees
Diseases of Fruits and Vegetables Volume I, 1Co-Authors: Lavern W. Timmer, S. N. Mondal, Natalia A. Peres, Alka BhatiaAbstract:Several important diseases of the fruit and foliage of citrus trees are addressed in this chapter: Postbloom fruit drop, caused by Colletotrichum acutatum; Alternaria brown spot, caused by Alternaria alternata; scab diseases, caused by Elsinoe fawsettii and E. australis; melanose, caused by Diaporthe Citri; and greasy spot caused by Mycosphaerella Citri. With each disease the history, economic importance, disease cycle, epidemiology, and control are covered. Special emphasis is placed on diagnosis and identification of the diseases and pathogens. Basic methods are presented for isolation of the pathogen, culture, production of various spore forms as well as for inoculation of plants to reproduce Koch’s postulates.
H. Takahashi - One of the best experts on this subject based on the ideXlab platform.
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Chemical structure of preinhibitin in citrus against citrus stem-end rot
Phytopathology, 1992Co-Authors: Y. Homma, T. Ohsawa, Y. Arimoto, H. TakahashiAbstract:When pedicels of Satsuma mandarin fruits on trees were inoculated with Diaporthe Citri and then harvested in early December and stored at room temperature, stem-end rot was not observed until late February. Numerous crystals were distributed in the tissues around the stem button. The dissolved crystals inhibited conidial germination and germ-tube elongation of D. Citri. The substance, referred to as the preinhibitin, was hydrolyzed by refluxing in ethyl alcohol-hydrochloric acid, 10:1, for 18 h. The resinous material obtained from the ether-soluble fraction was purified by repeated preparative thin-layer chromatography on silica gel to yield pale yellow crystals (...)
Feng Huang - One of the best experts on this subject based on the ideXlab platform.
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Endophytic Diaporthe associated with Citrus: A phylogenetic reassessment with seven new species from China
Fungal biology, 2015Co-Authors: Feng Huang, Xin Hou, Dhanushka Udayanga, Xinghong Wang, Xiufeng Mei, Kevin D. HydeAbstract:Phytopathogenic species of Diaporthe are associated with melanose, stem-end rot and gummosis diseases of Citrus. However, little is known about the occurrence of species of Diaporthe as endophytes and saprobes. In this study, we obtained 58 strains of Diaporthe, including 44 endophytic isolates from cultivated Citrus in China. The nuclear ribosomal internal transcribed spacer (ITS), partial sequences of translation elongation factor 1-α (EF1-α), beta-tubulin (TUB), and histone-3 (HIS) gene regions were analysed to determine the species of the isolates collected. In combined analysis of four gene regions, these strains grouped in 16 distinct clades in Diaporthe. The isolates were identified in Diaporthe arecae species complex, Diaporthe Citri, Diaporthe Citriasiana, Diaporthe Citrichinensis, Diaporthe endophytica, Diaporthe eres, Diaporthe hongkongensis, and Diaporthe sojae based on molecular phylogeny and morphology. Seven new species are described from Citrus namely, Diaporthe biconispora, Diaporthe biguttulata, Diaporthe discoidispora, Diaporthe multigutullata, Diaporthe ovalispora, Diaporthe subclavata, and Diaporthe unshiuensis with descriptions and illustrations.
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Diaporthe species occurring on citrus in China
Fungal Diversity, 2013Co-Authors: Feng Huang, Xin Hou, Megan M. Dewdney, Guoqing Chen, Kevin D. HydeAbstract:Diaporthe species are important pathogens of a wide range of hosts including many economically important crops. Diaporthe Citri is generally accepted to cause melanose of Citrus fruits, leaves and shoots; stem-end rot of fruits and gummosis of perennial branches. In this study, 147 strains of Diaporthe were isolated from diseased leaves, twigs, fruits and branches of Citrus from Shaanxi, Zhejiang, Guangxi, Fujian, Guangdong, Jiangxi, Hunan, Chongqing and Shanghai and identified by morphology and molecular analysis of nuclear ribosomal internal transcribed spacer (ITS), partial sequences of translation elongation factor 1-α (EF 1-α), tubulin (TUB) and calmodulin (CAL) genes. All strains from Citrus clustered in three clades. Diaporthe Citri was the predominant species and is compared with strains from Florida, USA, where this species was first collected and described. Two new taxa differing from D. Citri are described as D. Citriasiana and D. Citrichinensis in this paper. Inoculation tests indicate that all three species are able to cause stem-end rot of fruits, while only D. Citri could cause melanose on leaves.