scholarly journals Identification and pathogenicity of Alternaria species associated with leaf blotch disease and premature defoliation in French apple orchards

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e12496
Author(s):  
Kévin Fontaine ◽  
Céline Fourrier-Jeandel ◽  
Andrew D. Armitage ◽  
Anne-Laure Boutigny ◽  
Manuela Crépet ◽  
...  
Keyword(s):  
Species Complex ◽  
Common Disease ◽  
Pathogenicity Test ◽  
Taxonomic Assignment ◽  
Leaf Blotch ◽  
Specific Pcr ◽  
Tree Defoliation ◽  
Representative Subset ◽  
Golden Delicious ◽  
Detached Leaves

Leaf blotch caused by Alternaria spp. is a common disease in apple-producing regions. The disease is usually associated with one phylogenetic species and one species complex, Alternaria alternata and the Alternaria arborescens species complex (A. arborescens SC), respectively. Both taxa may include the Alternaria apple pathotype, a quarantine or regulated pathogen in several countries. The apple pathotype is characterized by the production of a host-selective toxin (HST) which is involved in pathogenicity towards the apple. A cluster of genes located on conditionally dispensable chromosomes (CDCs) is involved in the production of this HST (namely AMT in the case of the apple pathotype). Since 2016, leaf blotch and premature tree defoliation attributed to Alternaria spp. have been observed in apple-producing regions of central and south-eastern France. Our study aimed to identify the Alternaria species involved in apple tree defoliation and assess the presence of the apple pathotype in French orchards. From 2016 to 2018, 166 isolates were collected and identified by multi-locus sequence typing (MLST). This analysis revealed that all these French isolates belonged to either the A. arborescens SC or A. alternata. Specific PCR detection targeting three genes located on the CDC did not indicate the presence of the apple pathotype in France. Pathogenicity was assessed under laboratory conditions on detached leaves of Golden Delicious and Gala apple cultivars for a representative subset of 28 Alternaria isolates. All the tested isolates were pathogenic on detached leaves of cultivars Golden Delicious and Gala, but no differences were observed between the pathogenicity levels of A. arborescens SC and A. alternata. However, the results of our pathogenicity test suggest that cultivar Golden Delicious is more susceptible than Gala to Alternaria leaf blotch. Implications in the detection of the Alternaria apple pathotype and the taxonomic assignment of Alternaria isolates involved in Alternaria leaf blotch are discussed.

Colletotrichum Gloeosporioides Species Complex: Pathogen Causing Anthracnose, Gummosis and Die-Back Diseases of Cashew (Anacardium Occidentale L.) In Ghana

2020 ◽  
Vol 2 (6) ◽  
Author(s):  
A. Muntala ◽  
P. M. Norshie ◽  
K. G. Santo ◽  
C. K. S. Saba
Keyword(s):  
Species Complex ◽  
Colletotrichum Gloeosporioides ◽  
Potato Dextrose Agar ◽  
Causal Agent ◽  
Anacardium Occidentale ◽  
Causative Organism ◽  
Pathogenicity Test ◽  
Small Water ◽  
Colletotrichum Gloeosporioides Species Complex

A survey was conducted in twenty-five cashew (Anacardium occidentale) orchards in five communities in the Dormaa-Central Municipality of Bono Region of Ghana to assess the incidence and severity of anthracnose, gummosis and die-back diseases on cashew. Cashew diseased samples of leaves, stem, inflorescences, twigs, flowers, nuts and apples showing symptoms (e. g. small, water-soaked, circular or irregular yellow, dark or brown spots or lesions on leaves, fruits and flowers, sunken surface, especially on the apples, blight, gum exudates) were collected for isolation of presumptive causative organism. The pathogen was isolated after disinfecting the excised diseased pieces in 70% ethanol, plated on potato dextrose agar (PDA) and incubated at 28 oC for 3 to 7 days. The identity of the putative pathogen was morphologically and culturally confirmed as belonging to Colletotrichum gloeosporioides species complex using standard mycological identification protocols. The pathogen had varied conidia sizes of between 9-15 up to 20 μm in length and diameter of 3-6 μm. The conidia were straight and cylindrically shaped with rounded or obtuse ends. The septate mycelium was whitish-grey, velvety and cotton-like in appearance from the top. The results confirmed the presence of the pathogen in the orchards with incidence ranging from 6.9% and 14.0% for gummosis and averaged 22.9% for anthracnose infected orchards. The result of the pathogenicity test confirmed the isolates to be pathogenic on inoculated cashew seedlings and were consistently re-isolated, thereby establishing the pathogen as the true causal agent of the said diseases in cashew trees and thus completed the Koch’s postulate.

Wolbachia and Cytoplasmic Incompatibility in the CaliforniaCulex pipiensMosquito Species Complex: Parameter Estimates and Infection Dynamics in Natural Populations

Genetics ◽  
2003 ◽  
Vol 165 (4) ◽  
pp. 2029-2038 ◽  
Author(s):  
Jason L Rasgon ◽  
Thomas W Scott
Keyword(s):  
Species Complex ◽  
Cytoplasmic Incompatibility ◽  
Natural Populations ◽  
Wolbachia Infection ◽  
Field Conditions ◽  
Parameter Estimates ◽  
Infection Prevalence ◽  
Infection Frequency ◽  
Specific Pcr ◽  
Vector Borne

AbstractBefore maternally inherited bacterial symbionts like Wolbachia, which cause cytoplasmic incompatibility (CI; reduced hatch rate) when infected males mate with uninfected females, can be used in a program to control vector-borne diseases it is essential to understand their dynamics of infection in natural arthropod vector populations. Our study had four goals: (1) quantify the number of Wolbachia strains circulating in the California Culex pipiens species complex, (2) investigate Wolbachia infection frequencies and distribution in natural California populations, (3) estimate the parameters that govern Wolbachia spread among Cx. pipiens under laboratory and field conditions, and (4) use these values to estimate equilibrium levels and compare predicted infection prevalence levels to those observed in nature. Strain-specific PCR, wsp gene sequencing, and crossing experiments indicated that a single Wolbachia strain infects Californian Cx. pipiens. Infection frequency was near or at fixation in all populations sampled for 2 years along a >1000-km north-south transect. The combined statewide infection frequency was 99.4%. Incompatible crosses were 100% sterile under laboratory and field conditions. Sterility decreased negligibly with male age in the laboratory. Infection had no significant effect on female fecundity under laboratory or field conditions. Vertical transmission was >99% in the laboratory and ∼98.6% in the field. Using field data, models predicted that Wolbachia will spread to fixation if infection exceeds an unstable equilibrium point above 1.4%. Our estimates accurately predicted infection frequencies in natural populations. If certain technical hurdles can be overcome, our data indicate that Wolbachia can invade vector populations as part of an applied transgenic strategy for vector-borne disease reduction.

scholarly journals Current Classification and Diversity of Fusarium Species Complex, the Causal Pathogen of Fusarium Wilt Disease of Banana in Malaysia

Agronomy ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1955
Author(s):  
Anysia Hedy Ujat ◽  
Ganesan Vadamalai ◽  
Yukako Hattori ◽  
Chiharu Nakashima ◽  
Clement Kiing Fook Wong ◽  
...  
Keyword(s):  
Fusarium Oxysporum ◽  
Fusarium Wilt ◽  
Species Complex ◽  
Phylogenetic Trees ◽  
Fusarium Species ◽  
Morphological Characteristics ◽  
Pathogenicity Test ◽  
Fusarium Spp ◽  
Specific Primers ◽  
Fusarium Oxysporum Species Complex

The re-emergence of the Fusarium wilt caused by Fusarium odoratissimum (F. odoratissimum) causes global banana production loss. Thirty-eight isolates of Fusarium species (Fusarium spp.) were examined for morphological characteristics on different media, showing the typical Fusarium spp. The phylogenetic trees of Fusarium isolates were generated using the sequences of histone gene (H3) and translation elongation factor gene (TEF-1α). Specific primers were used to confirm the presence of F. odoratissimum. The phylogenetic trees showed the rich diversity of the genus Fusarium related to Fusarium wilt, which consists of F. odoratissimum, Fusarium grosmichelii, Fusarium sacchari, and an unknown species of the Fusarium oxysporum species complex. By using Foc-TR4 specific primers, 27 isolates were confirmed as F. odoratissimum. A pathogenicity test was conducted for 30 days on five different local cultivars including, Musa acuminata (AAA, AA) and Musa paradisiaca (AAB, ABB). Although foliar symptoms showed different severity of those disease progression, vascular symptoms of the inoculated plantlet showed that infection was uniformly severe. Therefore, it can be concluded that the Fusarium oxysporum species complex related to Fusarium wilt of banana in Malaysia is rich in diversity, and F. odoratissimum has pathogenicity to local banana cultivars in Malaysia regardless of the genotype of the banana plants.

scholarly journals Gibberellin promotion of physiological leaf spot in detached 'Golden Delicious' apple leaves.

1975 ◽  
Vol 23 (2) ◽  
pp. 126-130
Author(s):  
W.J. Kender ◽  
H. Jonkers
Keyword(s):  
Leaf Spot ◽  
Growth Substance ◽  
Apple Leaves ◽  
Golden Delicious ◽  
Detached Leaves

The development of leaf spot, a non-pathogenic disorder specific to the cv. Golden Delicious, was accelerated in detached leaves (whether previously unmarked or showing leaf spot) when these were cultured in solutions of GA3 or GA4+7 at 10, 50 or 100 mg/l for 72 h. About 15% of the foliage on the trees exhibited leaf spot at the time selected leaves were detached for culture. In a second experiment with cultured leaves the interaction of PBA and GA4+7 applied simultaneously was highly synergistic in increasing the severity of the disorder when compared with the effect of either growth substance alone. (Abstract retrieved from CAB Abstracts by CABI’s permission)

scholarly journals Rhizoctonia solani AG-1 IA infects both rice and signalgrass in the Colombian Llanos

2016 ◽  
Vol 46 (1) ◽  
pp. 65-71 ◽  
Author(s):  
Lina Maria Ramos-Molina ◽  
Edisson Chavarro-Mesa ◽  
Danilo Augusto dos Santos Pereira ◽  
María del Rosario Silva-Herrera ◽  
Paulo Cezar Ceresini
Keyword(s):  
Rhizoctonia Solani ◽  
Species Complex ◽  
Molecular Detection ◽  
Sheath Blight ◽  
Pathogenicity Test ◽  
Rice Sheath Blight ◽  
Specific Primers ◽  
5.8S Rdna ◽  
Foliar Blight ◽  
Rhizoctonia Oryzae

ABSTRACT Foliar blight and death of signalgrass (Urochloa spp.) pastures are caused by the Rhizoctonia solani fungus. This study aimed at determining which pathogens from the Rhizoctonia species complex are associated with leaf and sheath blight in Urochloa and rice, in the Colombian Llanos. Sympatric areas of Urochloa pastures adjacent to rice cropping areas were sampled using a linear transect system. The pathogens were identified using morphological traits, molecular detection based on specific primers and sequencing of the ITS-5.8S rDNA region. R. solani AG-1 IA predominated as the pathogen associated with foliar blight in all samples from U. brizantha cv. 'Toledo' and hybrid Urochloa cv. 'Mulato'. Besides R. solani AG-1 IA (18 % of the samples), Rhizoctonia oryzae-sativae (71 %) and Sclerotium hydrophilum (11 %) were also detected. In the cross-pathogenicity test, the R. solani AG-1 IA fungus was the most aggressive to Urochloa, while R. oryzae-sativae produced very mild infection symptoms. This is the first report of R. oryzae-sativae and S. hydrophilum associated with the complex of rice sheath blight diseases in Colombia.

scholarly journals First Report of a New Postharvest Fruit Rot on Apple Caused by Sphaeropsis pyriputrescens

Plant Disease ◽  
2004 ◽  
Vol 88 (2) ◽  
pp. 223-223 ◽  
Author(s):  
C. L. Xiao ◽  
J. D. Rogers ◽  
R. J. Boal
Keyword(s):  
Leading Edge ◽  
Preliminary Evidence ◽  
Apple Fruit ◽  
Causal Agent ◽  
Fruit Rot ◽  
Postharvest Disease ◽  
Fluorescent Light ◽  
Pathogenicity Test ◽  
First Report ◽  
Golden Delicious

During March to July 2003, a postharvest fruit rot was observed on ‘Golden Delicious’, ‘Granny Smith’, and ‘Red Delicious’ apples (Malus × domestica Borkh.) sampled from commercial packinghouses in Washington State. Losses as high as 24% in storage bins were observed in July on ‘Red Delicious’. The disease started at the stem bowl area or the calyx end of the fruit. Decayed fruit was apparently not wounded. Decayed areas were brown and firm. Internal decayed flesh appeared yellowish brown. On ‘Red Delicious’ apples, decayed fruit was apparently discolored from red to brown. As the disease advanced, pycnidia of a fungus might form on the stem, sepals, or the surface of decayed fruit. Pycnidia were 0.3 to 0.7 mm in diameter, black, and partially immersed in decayed tissues. To isolate the causal agent, decayed fruit was lightly sprayed with 70% ethanol and air dried. Fragments of diseased tissue were removed from the margin of diseased and healthy tissue and plated on acidified potato dextrose agar (PDA). A fungus was consistently isolated from decayed fruit with the symptoms described above. On PDA, the colonies of the fungus first appeared with dense hyaline mycelium and later turned light yellow to yellow. Black pycnidia of the fungus formed on 2- to 3-week-old oatmeal agar cultures at 20°C under 12-h alternating cycles of fluorescent light and dark. The fungus was identified as Sphaeropsis pyriputrescens Xiao & J. D. Rogers, based on the description of the fungus (1). Voucher specimens were deposited at the WSU Mycological Herbarium. Two isolates of the fungus recovered from decayed apples were tested for pathogenicity on apple. Fruit of ‘Golden Delicious’ and ‘Gala’ were surface-disinfested for 5 min in 0.5% NaOCl, rinsed, and air dried. Fruit was wounded with a sterile 4-mm-diameter nail head. A 4-mm-diameter plug from the leading edge of a 3-day-old PDA culture or plain PDA (control) was placed in the wound of each of 10 replicate fruit for each isolate or control. Fruit was tray packed with polyethylene liners and stored in cardboard boxes in air at 3°C, and decay was evaluated 2 weeks after inoculation. Five decayed fruits from each treatment were selected for reisolation of the causal agent. The experiment was conducted twice. In a separate pathogenicity test, two isolates (one each from apple and pear) were included in the test. Fruit of ‘Red Delicious’ apple was prepared and inoculated as the same manner described above, but fruit was stored in air at 0°C. The experiment was conducted twice. All fruit that were inoculated with the fungus developed decay symptoms. No decay developed on fruit in the controls. The same fungus was reisolated from decayed fruit. This indicates that isolates from apple and pear were pathogenic to apple. S. pyriputrescens is the causal agent of a newly reported postharvest disease on ‘d'Anjou’ pears (1). To our knowledge, this is the first report of this fungus causing postharvest fruit rot on apple. We propose ‘Sphaeropsis rot’ as the name of this new disease on apple and pear. Preliminary evidence suggests that infection of fruit by this fungus occurred in the orchard prior to storage. Reference: (1) C. L. Xiao and J. D. Rogers. Plant Dis. 88:114, 2004.

scholarly journals Morphological and Molecular Characteristics of Fungal Species Associated with Crown Rot of Strawberry in South Korea

2021 ◽  
Author(s):  
Oliul Hassan ◽  
Taehyun Chang
Keyword(s):  
South Korea ◽  
Root Rot ◽  
Species Complex ◽  
Sequence Data ◽  
Morphological Characteristics ◽  
Fungal Species ◽  
Crown Rot ◽  
Molecular Characteristics ◽  
Pathogenicity Test ◽  
Crown And Root Rot

Abstract Crown and root rot is the most important and destructive strawberry diseases in Korea as it causessubstantial economic loss. In August 2020, a severe outbreak of crown and root rot on strawberries (Fragaria×ananassa Duch.) was observed in the greenhouse at Sangju, South Korea. Infected plantlets displayed browning rot within the crown and root, stunted growth, and poor rooting. Thirty fungal isolates were procured from the affected plantlet. Isolates were identified based on morphological characteristics and pathogenicity test as well as sequence data obtained from internal transcribed spacer, large subunit ribosomal ribonucleic acid, translation elongation factor,and RNA polymerase Ⅱ-second largest subunit. Results showed that thecrown and root rot of strawberry in Korea was caused by three distinct fungal species:Fusarium oxysporum species complex, F. solani species complex, andPlectosphaerella cucumerina. To the best of our knowledge,F. solani species complex andP. cucumerinaare reported for the first time as the causal agents of the crown and root rot of strawberryin South Korea.Pathogenicity tests confirmed that these isolates are pathogenic to strawberry.Understanding the composition and biology of the pathogen population will be helpful toprovide effectivecontrol strategies for the disease.

scholarly journals Keragaman Cendawan Pascapanen pada Umbi Bawang Merah Varietas Bima Brebes

2019 ◽  
Vol 14 (5) ◽  
pp. 175
Author(s):  
Okky Setyawati Dharmaputra ◽  
Sri Listiyowati ◽  
Ira Zahara Nurwulansari
Keyword(s):  
Species Complex ◽  
Pathogenic Fungi ◽  
Colony Growth ◽  
Fusarium Fujikuroi ◽  
Molecular Characteristics ◽  
Hot Pepper ◽  
Pathogenicity Test ◽  
Fungal Isolation ◽  
Fungi Infection ◽  
Colletotrichum Gloeosporioides Species Complex

Diversity of Postharvest Fungi on Shallot Bulbs Variety Bima BrebesIn Indonesia, shallot (Allium ascalonicum) is horticultural main commodity after hot pepper. Significant yield losses can be caused by postharvest fungi infection. Research on the diversity of postharvest fungi on shallot bulbs has been conducted in some countries, unfortunately little is done in Indonesia. The study was aimed to obtain information on the diversity of postharvest fungi infecting shallot bulbs variety Bima Brebes from several traditional markets in Bogor City. Shallot bulbs were collected in January and February 2016. The study consisted of fungal isolation from shallot bulbs, fungal pathogenicity test, and identification of pathogenic fungi based on morphological and molecular characteristics. Morphology identification was based on the color of fungal colony, growth pattern, as well as somatic and reproduction structures. Several species of pathogenic fungi were successfully identified from shallot bulbs i.e. Alternaria alternata, Aspergillus niger, Colletotrichum gloeosporioides species complex, Fusarium fujikuroi species complex, F. oxysporum, F. solani, Penicillium citrinum and P. pinophilum.  Among these fungi, the highest pathogenicity was shown by C.  gloeosporioides species complex.

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