scholarly journals First Report of Colletotrichum nymphaeae Causing Anthracnose on Almond in Hungary

Plant Disease ◽  
2021 ◽  
Author(s):  
Virág Varjas ◽  
Sámuel László Szilágyi ◽  
Tamás Lakatos
Keyword(s):  
Species Complex ◽  
Prunus Dulcis ◽  
Colletotrichum Acutatum ◽  
Valid Species ◽  
Bootstrap Support ◽  
First Report ◽  
Pathogenicity Tests ◽  
Buda Hills ◽  
Genebank Collection

Almond (Prunus dulcis [Mill.] D. A. Webb) is cultivated in commercial orchards in southwestern Hungary while numerous backyard orchards predominate in Buda Hills and central Hungary. In July 2019, anthracnose symptoms and necrotic twigs were observed across almond genotypes in a meadow orchard of Óbuda and in the genebank collection of the Hungarian University of Agriculture and Life Sciences. Fruits of some genotypes were damaged 100%, whereas others to a lesser degree or asymptomatic. Orange slightly sunken lesions on fruits produced gum. Near the diseased fruits the young shoots shriveled, the stalks became necrotized, on twigs necrosis developed. Isolates obtained from orange conidial masses from epicarp, necrotized tissues from twigs, and stalks were grown on PDA for 7 days at 25 ֯C in the dark. Upper surfaces of the colonies were white to pale gray, black solid mycelial structures were formed, the reverse side varied white to salmon. Acervuli were not formed, but conidia were produced from hyphae. Conidia were unicellular, hyaline, smooth-walled, cylindrical, predominant with both end rounded, or one end acute. Morphometric measurements of conidia showed mean length ± SD × width ± SD = 18.0 ± 2.2 × 4.7 ± 0.6 μm (n = 100). The isolates were morphologically identified as Colletotrichum acutatum sensu lato (Damm et al. 2012). Sexual morph was not observed. Three monosporic isolates were used for molecular identification. Partial nucleotide sequences were amplified from three loci, internal transcribed spacer (ITS), β-tubulin (TUB2) and calmodulin (CAL) after White et al. (1990); Glass and Donaldson (1995) and Weir et al. (2012), respectively. The ITS sequences (GenBank accessions MW425388 to MW425390) of the three isolates revealed that they belong to the C. acutatum species complex while BLAST results showed that TUB2 sequences (GenBank accessions MW428285 to MW428287) had 99.3% identity with C. nymphaeae strain CBS515.78, whereas the CAL sequences (GenBank accessions MW428288 to MW428290) had 100% with C. nymphaeae strain FREC138. The phylogenetic tree containing all the valid species of C. acutatum species complex confirmed that the isolates clustered to C. nymphaeae with high bootstrap support. The fungus was identified as Colletotrichum nymphaeae (Pass) Aa based on morphometric and molecular biological evidence. In vivo pathogenicity tests were conducted on ten healthy fruits, and ten twigs by inserting mycelial agar plugs (5 mm in diameter) onto wounded pericarp and phloem tissues, which were then wrapped in wet cotton and Parafilm®. The control treatments received sterile PDA discs. After 15 days, necrotic lesions 12 to 19 mm in diameter developed on fruit, 9 to 18 mm on twig. Control fruits, and twigs were asymptomatic. Koch’s postulates were fulfilled with the reisolation of the pathogen from symptomatic tissues. The ITS, ACT and CAL sequences of the reisolated Colletotrichum were determined and found identical to the original isolates. Anthracnose symptoms are known on almond fruits in several almond growing regions all over the word caused by Colletotrichum acutatum, C. godetiae, C. fioriniae, C. simmondsii, and C. gloeosporioides (Adaskaveg et al. 1997; López-Moral et al. 2000; de Silva et al. 2021; Shabi et al. 1983;). To our knowledge, this is the first report of Colletotrichum nymphaeae causing anthracnose of almond globally.

scholarly journals Morphological, Pathogenic, and Molecular Characterization of Colletotrichum acutatum Isolates Causing Almond Anthracnose in Spain

Plant Disease ◽  
2017 ◽  
Vol 101 (12) ◽  
pp. 2034-2045 ◽  
Author(s):  
Ana López-Moral ◽  
Maria Carmen Raya-Ortega ◽  
Carlos Agustí-Brisach ◽  
Luis F. Roca ◽  
Maria Lovera ◽  
...  
Keyword(s):  
Molecular Characterization ◽  
Species Complex ◽  
Morphological Characteristics ◽  
Apple Fruit ◽  
Colletotrichum Acutatum ◽  
Pathogenicity Tests ◽  
Clear Identification ◽  
Colletotrichum Acutatum Species Complex ◽  
A New Species

Almond anthracnose is a serious and emerging disease in several countries. All isolates causing almond anthracnose have been assigned to the Colletotrichum acutatum species complex, of which only C. fioriniae and C. godetiae have been associated with the disease to date. Here, we characterized Colletotrichum isolates from almond fruit affected by anthracnose in the Andalusia region. Two Colletotrichum isolates causing olive anthracnose were included for comparison. Morphological characteristics were useful for separating the isolates into groups based on colony morphology. Pathogenicity tests in almond, olive, and apple fruit showed differences in virulence and some degree of pathogenic specialization among isolates. Molecular characterization allowed clear identification of the Colletotrichum isolates tested. The olive isolates were identified as C. godetiae and C. nymphaeae, both previously identified in Andalusian olive orchards. Two phylogenetic species were identified among the almond isolates: C. godetiae, with gray colonies, which is well known in other countries, and C. acutatum, with pink-orange colonies. This species identification differs from those of pink-colony subpopulations described in other countries, which are C. fioriniae. Therefore, this study is also the first report of a new species of Colletotrichum causing almond anthracnose within the C. acutatum species complex.

scholarly journals First report of preharvest fruit rot of ‘Pink Lady’ apples caused by Colletotrichum fructicola in Italy

Plant Disease ◽  
2021 ◽  
Author(s):  
Marcel Wenneker ◽  
Khanh Pham ◽  
Engelien Kerkhof ◽  
Dalphy O.C. Harteveld
Keyword(s):  
Species Complex ◽  
Management Strategies ◽  
Morphological Characteristics ◽  
Late Summer ◽  
Fruit Rot ◽  
Colletotrichum Acutatum ◽  
Apple Orchards ◽  
First Report ◽  
Bitter Rot ◽  
Colletotrichum Fructicola

In late summer 2019, a severe outbreak of fruit rot was observed in commercial ‘Pink Lady’ apple orchards (>20 ha in total) in the region Emilia-Romagna (Northern Italy). The symptoms on the fruit appeared as small circular red to brown lesions. Disease incidences of over 50% of the fruits were observed. To isolate the causal agent, 15 affected apples were collected and small portions of fruit flesh were excised from the lesion margin and placed on potato dextrose agar (PDA). The plates were incubated at 20°C in the dark, and pure cultures were obtained by transferring hyphal tips on PDA. The cultures showed light to dark gray, cottony mycelium, with the underside of the culture being brownish and becoming black with age. Conidia (n=20) were cylindrical, aseptate, hyaline, rounded at both ends, and 12.5 to 20.0 × 5.0 to 7.5 μm. The morphological characteristics were consistent with descriptions of Colletotrichum species of the C. gloeosporioides species complex, including C. fructicola (Weir et al. 2012). The identity of two representative isolates (PinkL2 & PinkL3) from different apples was confirmed by means of multi-locus gene sequencing. Genomic DNA was extracted using the LGC Mag Plant Kit (Berlin, Germany) in combination with the Kingfisher method (Waltham, USA). Molecular identification was conducted by sequencing the ITS1/ITS4 region and partial sequences of four other gene regions: chitin synthase (CHS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), actin (ACT), and beta-tubulin (TUB). The sequences have been deposited in GenBank under accession numbers MT421924 & MT424894 (ITS), MT424612 & MT424613 (CHS), MT424616 & MT424617 (GAPDH), MT424614 & MT424615 (ACT), and MT424620 & MT424621 (TUB). MegaBLAST analysis revealed that our ITS sequences matched with 100% identity to Colletotrichum fructicola (Genbank JX010177). The CHS, GAPDH, ACT and TUB sequences of both isolates were 100% identical with C. fructicola culture collection sequences in Genbank (JX009807, JX009923, JX009436 and JX010400, respectively), confirming the identity of these isolates as C. fructicola. Koch's postulates were performed with 10 mature ‘Pink Lady’ apples. Surface sterilized fruit were inoculated with 20 μl of a suspension of 105 conidia ml–1 after wounding with a needle. The fruits were incubated at 20˚C at high relative humidity. Typical symptoms appeared within 4 days on all fruit. Mock-inoculated controls with sterile water remained symptomless. The fungus was reisolated and confirmed as C. fructicola by morphology and sequencing of all previously used genes. Until recently the reported causal agents of bitter rot of apple in Europe belong to the Colletotrichum acutatum species complex (Grammen et al. 2019). C. fructicola, belonging to C. gloeosporioides species complex, is known to cause bitter rot of apple in the USA, Korea, Brazil, and Uruguay (Kim et al. 2018; Velho et al. 2015). There is only one report of bitter rot associated with C. fructicola on apple in Europe (France) (Nodet et al. 2019). However, C. fructicola is also the potential agent of Glomerella leaf spot (GLS) of apple (Velho et al. 2015; 2019). To the best of our knowledge this is the first report of C. fructicola on apples in Italy. It is important to stress that the C. gloeosporioides species complex is still being resolved and new species on apple continue to be identified, e.g. C. chrysophilum that is very closely related to C. fructicola (Khodadadi et al. 2020). Given the risks of this pathogen the presence of C. fructicola in European apple orchards should be assessed and management strategies developed.

scholarly journals First Report of Colletotrichum acutatum on Strawberry in Northwestern Argentina

Plant Disease ◽  
2000 ◽  
Vol 84 (6) ◽  
pp. 706-706 ◽  
Author(s):  
C. J. Ramallo ◽  
L. D. Ploper ◽  
M. Ontivero ◽  
M. P. Filippone ◽  
A. Castagnaro ◽  
...  
Keyword(s):  
Colletotrichum Acutatum ◽  
Conidial Suspension ◽  
Disease Symptoms ◽  
Northwestern Argentina ◽  
First Report ◽  
Surface Control ◽  
Detached Leaves ◽  
Strawberry Anthracnose ◽  
Pathogenicity Tests ◽  
Necrotic Spots

Isolates were obtained from strawberry tissue with anthracnose symptoms from several locations near Tucumán, Argentina. Isolates were characterized using several criteria. Isolates produced fusiform conidia, tapered to a point at both ends, and averaged 13.5 × 4.9 μm. On potato dextrose agar, colonies produced a white cottony mycelial colony that turned orange in older cultures. Compared with Colletotrichum fragariae, the new isolates produced fewer appressoria. Pathogenicity tests were conducted on detached leaves and plants in the greenhouse and field. Detached immature leaves of cvs. Chandler, Fern, and Sweet Charlie were inoculated with a 20-μl droplet of an aqueous conidial suspension (106 conidia per ml) placed on the adaxial surface. Control leaves were inoculated with sterile distilled water. Leaves were maintained under white light (2,000 lux, 12 h/day) at 26°C, and 100% relative humidity. Necrotic spots were visible 4 days after inoculation. Greenhouse and field plants were spray-inoculated and covered for 48 h. Disease symptoms were mainly observed on petioles and runners 9 days after inoculation. No lesions were observed on control detached leaves or plants. Koch's postulates were confirmed in all cases. Based on morphological and cultural characteristics, isolates were identified as C. acutatum Simmonds (1). This is the first report of C. acutatum causing strawberry anthracnose in northwestern Argentina. Reference: (1) B. Smith and L. L. Black. Plant Dis. 74:69, 1990.

scholarly journals First Report of Anthracnose Caused by Colletotrichum gloeosporioides on Schefflera actinophylla in China

Plant Disease ◽  
2013 ◽  
Vol 97 (7) ◽  
pp. 998-998
Author(s):  
J. Huang
Keyword(s):  
Dna Sequence ◽  
Species Complex ◽  
Colletotrichum Gloeosporioides ◽  
Conidial Suspension ◽  
First Report ◽  
Leaf Spots ◽  
Black Spots ◽  
Pathogenicity Tests ◽  
Colletotrichum Gloeosporioides Species Complex ◽  
And Control

In China, in mild to warm climates, Schefflera actinophylla is commonly grown as a decorative tree in gardens. When mature, it has bright red flowers in inflorescences with up to 20 racemes that develop in summer or early autumn. From 2008 to 2011, lesions were observed on young and mature leaves in several locations in Guangzhou, China. The first symptoms were circular, necrotic areas that usually developed into irregular, dry, brown to reddish brown or black spots. Spots often first appeared at or near the margins of leaves. Reproductive bodies of the pathogen appeared as black specks in leaf spots. Under a 10× magnification, black, needle-like fungal structures (setae) were observed in the centers of spots on the upper leaf surface. A fungus was isolated from the lesion and was identified as Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. based on cultural characteristics and conidial morphology (1). The voucher isolates were deposited in the Institute of Plant Pathology, Zhongkai University of Agriculture and Engineering. C. gloeosporioides is a species complex (2) and there is a degree of unresolved aspects of taxonomy in this species complex. Cultures on potato dextrose agar (PDA) had aerial white mycelium that turned gray to grayish black after 10 days at 25°C and a 12-h photoperiod and produced salmon to orange conidial masses. Brown, 80 to 120 μm long setae were observed in the acervulus. Conidia 14.1 to 18.0 × 4.0 to 6.1 μm in size were hyaline, thin-walled, aseptate, granular inside, clavate to slightly navicular in shape with an obtuse apex and a truncate base. To identify the fungus, a 588-bp segment of the ITS1-5.8S-ITS2 rDNA region was amplified by PCR and sequenced. The DNA sequence was submitted to GenBank as KC207404. A BLAST search of the DNA sequence showed 99% identity with accessions AY266389.1, EF423519.1, and HM575258.1 of C. gloeosporioides. Pathogenicity tests were conducted under greenhouse conditions at 25 ± 2°C. A total of 15 leaves from three 1-year-old S. actinophylla plants were inoculated with mycelial PDA plugs that were placed on 0.5-cm2 leaf wounds and then wrapped with Parafilm. Control leaves were treated similarly except that they were inoculated with PDA plugs without the fungus. No symptoms developed on control leaves after 10 days. Foliar lesions on inoculated leaves closely resembled those observed in the field. C. gloeosporioides was reisolated consistently from inoculated leaves. Pathogenicity was also tested by spraying leaves of potted S. actinophylla plants about 30 cm in height with 10 ml of a conidial suspension (1 × 105 conidia/ml) prepared from 7-day-old PDA cultures grown at 25°C. Leaves sprayed with distilled water were used as controls. Three plants were inoculated in each of two experiments and were incubated at 25°C and 90% relative humidity in a growth chamber. Tiny brown spots started to develop on all inoculated leaves 5 days after inoculation and the progression of symptom development was similar to that observed in the field. Control leaves remained asymptomatic. C. gloeosporioides was reisolated from inoculated leaves. To my knowledge, this is the first report of C. gloeosporioides causing anthracnose on S. actinophylla in China. References: (1) B. C. Sutton. The genus Glomerella and its anamorph Colletotrichum. In: Colletotrichum Biology, Pathology and Control. CAB International, Wallingford, UK, 1992. (2) B. S. Weir et al. The Colletotrichum gloeosporioides species complex. Stud. Mycol. 73:115, 2012.

scholarly journals First Report of the Anamorph of Glomerella acutata Causing Anthracnose on Avocado Fruits in Mexico

Plant Disease ◽  
2007 ◽  
Vol 91 (9) ◽  
pp. 1200-1200 ◽  
Author(s):  
G. Avila-Quezada ◽  
H. V. Silva-Rojas ◽  
D. Teliz-Ortiz
Keyword(s):  
Colletotrichum Gloeosporioides ◽  
Soft Rot ◽  
Lower Surface ◽  
Persea Americana ◽  
Colletotrichum Acutatum ◽  
Morphological Identification ◽  
Internal Transcribed Spacer Region ◽  
First Report ◽  
Mexican State ◽  
Pathogenicity Tests

Mexico is a major avocado (Persea americana) producer in the world. Glomerella cingulata (anamorph Colletotrichum gloeosporioides) has been reported as a causal agent of anthracnose on avocado fruits worldwide (3), while G. acutata (anamorph Colletotrichum acutatum) has been identified as the cause of this disease only in New Zealand (2) and Australia (4). This study was done with the objective to determine the Glomerella spp. involved as the causal agents of avocado anthracnose in Mexico. From 2003 to 2006, avocado fruits cv. Hass with anthracnose symptoms appearing as brown-black lesions on the pericarp and soft rot in the mesocarp were collected in 10 counties in Michoacan, the leading avocado-producing Mexican state. Glomerella spp. were isolated on potato dextrose agar (PDA) for molecular and morphological identification. A phylogenetic analysis was done by amplifying the internal transcribed spacer region of rDNA for 28 of the isolates. Primers ITS5/NL4 was used and successfully amplified bands of approximately 1,000 bp. Each sequence corresponding to Glomerella spp. was compared with sequences deposited in the GenBank database using BLAST. The results from molecular approach indicated 86% of the isolates used in this study were G. cingulata and 14% were G. acutata. Sequences of both species were deposited in GenBank under Accession Nos. EF221828, EF221829, and EF221830 for G. cingulata and EF175780, EF221831, and EF221832 for G. acutata. Colonies of G. acutata that developed on PDA medium were pale gray, occasionally the lower surface was olive green, and the center was covered with orange-to-salmon pink masses of conidia and perithecia. Conidia grown in the same media were straight, fusiform, 8.2 to 16.5 μm long, and 2.7 to 4.0 μm wide (4). Pathogenicity tests of G. acutata were carried out by inoculating six healthy cv. Hass fruits (1) at three evenly spaced locations on the fruit surface with a needle dipped in a conidial mass from a 3-day-old monoconidial culture of G. acutata. Fruits were then incubated in a moist chamber for 3 days. Anthracnose symptoms were observed on healthy fruits inoculated with G. acutata, while control fruits inoculated with sterile water did not develop symptoms. The fungi were reisolated successfully to confirm the pathogen's identity using morphological key. To our knowledge, this is the first report of G. acutata causing anthracnose on avocado fruits in Mexico. References: (1) R. Guetsky et al. Phytopathology 95:1341, 2005. (2) W. F. T. Hartill. N. Z. J. Crop Hortic. Sci. 19:297, 1991. (3) D. Prusky. Annu. Rev. Phytopathol. 34:413, 1996. (4) J. H. Simmonds. Qld. J. Agric. Anim. Sci. 22:437, 1965.

scholarly journals First report of Colletotrichum fioriniae and C. nymphaeae as Causal Agents of anthracnose on walnut in Italy

Plant Disease ◽  
2021 ◽  
Author(s):  
LUONGO LAURA ◽  
Massimo Galli ◽  
Ivana Garaguso ◽  
Mariangela Petrucci ◽  
Salvatore Vitale
Keyword(s):  
Juglans Regia ◽  
Fruit Production ◽  
Internal Transcribed Spacers ◽  
Colletotrichum Acutatum ◽  
Distilled Water ◽  
First Report ◽  
Randomized Design ◽  
Black Spots ◽  
Sterile Needle ◽  
Pathogenicity Tests

English walnut (Juglans regia L.) is species grown either for high quality wood or fruit production. In Italy walnut cultivation occupies an area of about 4600 ha (FAOSTAT, http://www.fao.org/faostat, 2020). In 2019-2020, walnut fruits (cv Lara) with anthracnose symptoms were collected from walnut orchards in Province of Venice (Northern Italy). Affected fruits showed necrotic and circular lesions with acervuli in the center causing the complete mummification of the fruit as described by Da Lio et al., 2018. Orange conidial masses appeared under wet conditions. The fungus was isolated from necrotic tissues and conidial masses were put on potato dextrose agar (PDA) medium. Plates were incubated at 25°C for 5 to 7 days. The colonies were white to pink on the upper side and pink with black spots on the reverse. Acervuli formed and produced conidial masses on PDA after 6 days. Culture and conidial morphology were in concordance with published descriptions of C. acutatum sensu lato (Damm et al., 2012). To confirm the identity, internal transcribed spacers (ITS), (glyceraldehyde-3-phosphate dehydrogenase (GAPDH), actin (ACT) and beta-tubulin (TUB2) genes were amplified and sequenced using the primer pairs ITS1/ITS4 (White at al. 1990), GDF1/GDR1 (Guerber et al., 2003), ACT512F/ACT783R and BT2Fd/BT4R primers (Da Lio et al., 2018). The isolates belonged to two different species of Colletotrichum acutatum complex: C. fioriniae (Marcelino & Gouli) and C. nymphaeae (Pass). Sequences of two representative isolates C. fioriniae CREADC-F2317 and C. nymphaeae CREADC-F2372 were deposited in GenBank with accession numbers MZ153170 and MZ191794 (ITS), MZ203522 and MZ224013 (GAPDH), MZ203521 and MZ224012 (ACT), and MZ203523 and MZ224014 (TUB2). For all the genes, isolates had a 100% similarity to multiple C. fioriniae and C. nymphaeae accessions, respectively. Maximum likelihood trees based on concatenated sequences of the four genes were constructed using MEGA 6.0 (Tamura et al., 2013). The phylogenetic analysis grouped the isolates in the C. fioriniae and nymphaeae clusters respectively. The two isolates CREADC-F2317 and CREADC-F2372 were used to confirm pathogenicity on walnut fruits. Fruits of cv Lara were surface disinfected by dipping in 3% NaOCl for 1 min, rinsed in sterile distilled water, and arranged in sterile humid chambers. Fruits were wounded with a sterile needle then inoculated with 20 μl of 106 conidia/ml suspensions of each isolate (one wound per fruit). Fruit treated with sterile distilled water served as a control. Inoculations were conducted on three fruits per replicate and three replicates per treatment arranged in a complete block randomized design. After 7 days incubation at 25 ± 1°C, all the inoculated fruits showed typical anthracnose symptoms and lesions with cream to salmon pink acervuli, whereas the controls remaied healthy. The species C. nymphaeae and C. fioriniae were reisolated from the rotted fruit. Pathogenicity tests were repeated twice with the same results. The morphology of the reisolated fungi was consistent with the inoculated one, fulfilling Koch’s postulates. The species C. fioriniae and C. nymphaeae have been described affecting numerous species worldwide (Damm et al., 2012). C. fioriniae and C. nymphaeae have been previously reported to cause severe anthracnose on walnut, C. fioriniae in France (Da Lio et al., 2018) and Hungary (Varjas et al., 2019) and C. nymphaeae in France (Da Lio et al., 2018) and Brazil (Savian et al., 2019). To our knowledge, this is the first report of C. fioriniae and C. nymphaeae as causal agents of walnut anthracnose in Italy.

scholarly journals Atividade do óleo de Eucalyptus citriodora e Azadirachta indica no controle de Colletotrichum acutatum em morangueiro

2010 ◽  
Vol 36 (3) ◽  
pp. 228-232 ◽  
Author(s):  
Cláudia Regina Dias-Arieira ◽  
Lucas da Rocha Ferreira ◽  
Jailson de Oliveira Arieira ◽  
Edenilson Gonçalves Miguel ◽  
Mateus Augusto Donega ◽  
...  
Keyword(s):  
Azadirachta Indica ◽  
Colletotrichum Acutatum ◽  
Eucalyptus Citriodora

A flor-preta é uma das doenças mais importantes do morangueiro e a busca por alternativas de controle tem sido uma constante, principalmente em áreas de cultivo orgânico. Assim, objetivou-se avaliar a eficiência, in vitro e in vivo, dos óleos de Eucalyptus citriodora e Azadirachta indica no controle de Colletotrichum acutatum em morangueiro. No experimento in vitro determinou-se a inibição do crescimento micelial quando o fungo foi submetido aos extratos nas concentrações de 0; 0,25; 0,5; 1,0 e 1,5%. No campo, avaliou-se o controle da doença com a aplicação dos óleos nas concentrações de 0, 0,5 e 1,0%, pulverizados em intervalos de 7, 15 e 30 dias, em plantas inoculadas com suspensão de 10(6) conídios/mL. As avaliações foram realizadas semanalmente, observando-se a ocorrência e tamanho de lesões no pedúnculo e nos frutos, abortamento floral, produtividade, e ocorrência natural da doença. In vitro todos os tratamentos apresentaram redução significativa do crescimento micelial do fungo quando comparados ao controle. No campo, apenas o óleo de nim apresentou efeito significativo, reduzindo o abortamento floral e a ocorrência de frutos doentes advindos de flores inoculadas. Porém, maior ocorrência natural de doença foi observada quando a dosagem de 1,0% foi aplicada semanalmente.

scholarly journals First Report of Pythium Root Rot of Rau Ram (Polygonum odoratum)

Plant Disease ◽  
2005 ◽  
Vol 89 (3) ◽  
pp. 340-340
Author(s):  
E. N. Rosskopf ◽  
C. B. Yandoc ◽  
B. Stange ◽  
E. M. Lamb ◽  
D. J. Mitchell
Keyword(s):  
Root Rot ◽  
Vascular System ◽  
Pond Water ◽  
Centraalbureau Voor ◽  
First Report ◽  
Pathogenicity Tests ◽  
Symptomatic Tissue ◽  
Pythium Helicoides ◽  
Production House ◽  
Test Plants

Polygonum odoratum (= Persicaria odorata), known as rau ram or sang hum, is native to southeastern Asia and is a common herb in Vietnamese cuisine (1). It has been studied most extensively for its aromatic compound content (2). In Florida, rau ram commonly is grown hydroponically in greenhouses using large, cement beds with recirculated water. The plants form dense mats from which new growth is trimmed for market. During January of 2002, a severe dieback was observed in one production house in Saint Lucie County, FL. Plants with less severe symptoms were yellowed and stunted. Roots of symptomatic plants were largely decayed with root symptoms beginning as a tip necrosis. The cortex of severely affected roots slipped off easily, leaving a stringy vascular system. Plating of symptomatic tissue from 20 randomly selected plant samples was performed with multiple general and selective media including potato dextrose agar, corn meal agar with pimaricin, ampicillin, rifampicin, and pentachloronitrobenzene (PARP) (3). All colonies produced were identified as Pythium helicoides Drechsler on the basis of sporangial, oogonial, and antheridial characteristics (4). Isolates had proliferous, obovoid, papillate sporangia, and were homothallic with smooth-walled oogonia and thick-walled, aplerotic oospores. Multiple antheridial attachments per oogonium were common with the antheridium attached along its entire length. Pathogenicity tests were conducted using P. odoratum plants grown from commercial transplants. Two tests were performed. Each test was conducted using eight inoculated and eight control plants. In the first test, plants were maintained in 10-cm pots immersed in sterilized pond water for the duration of the test. Plants were inoculated with five 7- × 70-mm sections of freshly growing mycelial culture per plant using 10-day-old cultures of Pythium helicoides grown on water agar. Chlorosis was observed at approximately 2 months after inoculation. Root necrosis was observed in inoculated plants approximately 5 months after inoculation. This test was performed in the greenhouse with temperatures ranging from 20 to 30°C. The second test was performed in growth chambers at 35 to 40°C. Plants were maintained in 10-cm pots immersed in Hoagland's solution and were inoculated with four 6-mm plugs per plant. Symptoms were observed on inoculated plants at this temperature within 1 week of inoculation. No chlorosis or root decay was observed in noninoculated, immersed plants. The pathogen was reisolated from inoculated, symptomatic tissue. To our knowledge, this is the first report of root rot of P. odoratum caused by Pythium helicoides. References: (1) R. E. Bond. Herbarist 55:34, 1989. (2) N. X. Dung et al. J. Essent. Oil Res. 7:339, 1995. (3) M. E. Kannwischer and D. J. Mitchell. Phytopathology 68:1760, 1978. (4) A. J. van der Plaats-Niterink. Monograph of the Genus Pythium. Vol. 21, Studies in Mycology. Centraalbureau voor Schimmelcutltures, Baarn, The Netherlands, 1981.

scholarly journals First Report of Anthracnose of Papaya (Carica papaya L.) Caused by Colletotrichum siamense in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Yujie Zhang ◽  
Wenxiu Sun ◽  
Ping Ning ◽  
Tangxun Guo ◽  
SuiPing Huang ◽  
...  
Keyword(s):  
Carica Papaya ◽  
Disease Incidence ◽  
Aerial Mycelium ◽  
Postharvest Disease ◽  
Distilled Water ◽  
First Report ◽  
Surface Samples ◽  
Initial Symptoms ◽  
Colletotrichum Siamense ◽  
Pathogenicity Tests

Papaya (Carica papaya L.) is a rosaceous plant widely grown in China, which is economically important. Anthracnose caused by Colletotrichum sp. is an important postharvest disease, which severely affects the quality of papaya fruits (Liu et al., 2019). During April 2020, some mature papaya fruits with typical anthracnose symptoms were observed in Fusui, Nanning, Guangxi, China with an average of 30% disease incidence (DI) and over 60% DI in some orchards. Initial symptoms of these papayas appeared as watery lesions, which turned dark brown, sunken, with a conidial mass appearing on the lesions under humid and warm conditions. The disease severity varied among fruits, with some showing tiny light brown spots, and some ripe fruits presenting brownish, rounded, necrotic and depressed lesions over part of their surface. Samples from two papaya plantations (107.54°E, 22.38°N) were collected, and brought to the laboratory. Symptomatic diseased tissues were cut into 5 × 5 mm pieces, surface sterilized with 2% (v/v) sodium hypochlorite for 1 minute, and rinsed three times with sterilized water. The pieces were then placed on potato dextrose agar (PDA). After incubation at 25°C in the dark for one week, colonies with uniform morphology were obtained. The aerial mycelium on PDA was white on top side, and concentric rings of salmon acervuli on the underside. A gelatinous layer of spores was observed on part of PDA plates after 7 days at 28°C. The conidia were elliptical, aseptate and hyaline (Zhang et al., 2020). The length and width of 60 conidia were measured for each of the two representative isolates, MG2-1 and MG3-1, and these averaged 13.10 × 5.11 μm and 14.45 × 5.95 μm. DNA was extracted from mycelia of these two isolates with the DNA secure Plant Kit (TIANGEN, Biotech, China). The internal transcribed spacer (ITS), partial actin (ACT), calmodulin (CAL), chitin synthase (CHS), β-tubulin 2 (TUB2) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) regions were amplified by PCR and sequenced. The sequences were deposited into GenBank with accessions MT904003, MT904004, and MT898650 to MT898659. BLASTN analyses against the GenBank database showed that they all had over 99% identity to the type strain of Colletotrichum siamense isolate ICMP 18642 (GenBank accession numbers JX010278, GQ856775, JX009709, GQ856730, JX010410, JX010019) (Weir et al., 2012). A phylogenetic tree based on the combined ITS, ACT, CAL, CHS, TUB2 and GAPDH sequences using the Neighbor-joining algorithm also showed that the isolates were C. siamense. Pathogenicity tests were conducted on 24 mature, healthy and surface-sterilized papaya fruits. On 12 papaya fruits, three well separated wounded sites were made for inoculation, and for each wounded site, six adjacent pinhole wounds were made in a 5-mm-diameter circular area using a sterilized needle. A 10 µl aliquot of 1 × 106 conidia/ml suspension of each of the isolates (MG2-1 and MG3-1) was inoculated into each wound. For each isolate, there were six replicate fruits. The control fruits were inoculated with sterile distilled water. The same inoculation was applied to 12 non-wound papaya fruits. Fruits were then placed in boxes which were first washed with 75% alcohol and lined with autoclaved filter paper moistened with sterilized distilled water to maintain high humidity. The boxes were then sealed and incubated at 28°C. After 10 days, all the inoculated fruits showed symptoms, while the fruits that were mock inoculated were without symptoms. Koch's postulates were fulfilled by re-isolation of C. siamense from diseased fruits. To our knowledge, this is the first report of C. siamense causing anthracnose of papaya in China. This finding will enable better control of anthracnose disease caused by C. siamense on papaya.

scholarly journals First Report of Anthracnose Caused by Colletotrichum acutatum on Persimmon Fruit in the United States

Plant Disease ◽  
2010 ◽  
Vol 94 (5) ◽  
pp. 634-634 ◽  
Author(s):  
S. M. Williamson ◽  
T. B. Sutton
Keyword(s):  
United States ◽  
Filter Paper ◽  
The United States ◽  
Grocery Store ◽  
Fruit Rot ◽  
Colletotrichum Acutatum ◽  
Diospyros Kaki ◽  
Japanese Persimmon ◽  
First Report ◽  
Persimmon Fruit

Persimmon trees are important for their fruit as well as their colorful fruit and foliage in the fall. Persimmon fruit (Japanese persimmon, Diospyros kaki cv. Fuyu) were collected in November 2008 from a tree in Windsor, NC, located in the Coastal Plain. Fruit were not symptomatic on the tree but developed dark lesions after harvest. Isolations from six fruit yielded seven isolates of Colletotrichum acutatum J. H. Simmonds. After incubation at 25°C under continuous light for 15 days on potato dextrose agar (PDA), all isolates had gray aerial mycelium, but the inverse sides of the plates of six isolates were maroon and one was beige. Masses of salmon-colored conidia were formed first in the center of the colonies, then were observed scattered across the colonies in older cultures. Conidia were hyaline, one-celled, elliptic with one or both ends pointed, and measured 8.1 to 16.3 × 3.1 to 5 μm. Setae and sclerotia were not observed. There were also dark structures measuring 1 to 10 mm that were partially embedded in the agar that contained conidia. Cultural and conidial characteristics of the isolates were similar to those of C. acutatum (3). PCR amplification was performed with the species-specific primer pair CaInt2/ITS4 (2) and genomic DNA from the original isolates and isolates obtained from inoculated fruit. An amplification product of approximately 490 bp, which is specific for C. acutatum, was observed. To fulfill Koch's postulates, persimmon fruit obtained from the grocery store were surface disinfested with 0.5% sodium hypochlorite and sterile filter paper disks dipped in conidial suspensions (1 × 105 conidia/ml) of two C. acutatum isolates (maroon and beige reverse) or sterile, deionized water were placed on the fruit. Three fruit were inoculated per treatment and the disks were placed on four locations on each fruit. Parafilm was wrapped around the diameter of the fruit to keep the filter paper disks moist and in place. Fruit were placed in moist chambers and incubated at 25°C. After 3 days, the Parafilm was removed and the fruit returned to the moist chambers. Small, dark lesions were observed on fruit inoculated with each isolate of C. acutatum when the filter paper disks were removed. Ten days after inoculation, dark lesions and acervuli with salmon-colored masses of conidia were observed on fruit inoculated with both isolates of C. acutatum and the fruit were soft. After 12 days, there were abundant masses of conidia and the inoculated areas were decayed. Control fruit remained firm and did not develop symptoms. Cultures obtained from the fruit and the conidia produced were typical of the isolates used to inoculate the fruit. C. acutatum has been reported to cause fruit rot on persimmon fruit in New Zealand (1). To our knowledge, this is the first report of C. acutatum on persimmon fruit in the United States. References: (1) R. Lardner et al. Mycol. Res. 103:275, 1999. (2) S. Sreenivasaprasad et al. Plant Pathol. 45:650, 1996. (3) B. C. Sutton. Page 523 in: Coelomycetes. Commonwealth Agricultural Bureaux, Great Britain. 1980.

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