First report of Aspergillus awamori as a fungal pathogen of garlic (Allium sativum L.)

Lemon (Citrus lemon (L.) Burm. f.) is an important fruit crop cultivated worldwide, and is grown practically in every state in India (3). During a survey conducted in 2013, a few small trees in a lemon orchard near Mysore city (Karnataka) (12°19.629′ N, 76°31.892′ E) were found affected by dieback disease. Approximately 10 to 20% of trees were affected as young shoots and branches showed progressive death from the apical region downward. Different samples were collected and diagnosed via morphological methods. The fungus was consistently isolated from the infected branches when they were surface sanitized with 1.5% NaOCl and plated on potato dextrose agar (PDA). Plates were incubated at 26 ± 2°C for 7 days at 12/12 h alternating light and dark period. Fungal colonies were whitish with pale brown stripes having an uneven margin and pycnidia were fully embedded in the culture plate. No sexual state was observed. Pycnidia were globose, dark, 158 to 320 μm in diameter, and scattered throughout the mycelial growth. Both alpha and beta conidia were present within pycnidia. Alpha conidia were single celled (5.3 to 8.7 × 2.28 to 3.96 μm) (n = 50), bigittulate, hyaline, with one end blunt and other truncated. Beta conidia (24.8 to 29.49 × 0.9 to 1.4 μm) (n = 50) were single celled, filiform, with one end rounded and the other acute and curved. Based on the morphological and cultural features, the fungal pathogen was identified as Phomopsis citri H.S. Fawc. Pathogenicity test was conducted on nine healthy 2-year-old lemon plants via foliar application of a conidial suspension (3 × 106); plants were covered with polythene bags for 6 days and maintained in the greenhouse. Sterile distilled water inoculated plants (in triplicate) served as controls and were symptomless. Development of dieback symptoms was observed after 25 days post inoculation and the fungal pathogen was re-isolated from the inoculated lemon trees. The internal transcribed spacer region (ITS) of the isolated fungal genomic DNA was amplified using universal-primer pair ITS1/ITS4 and sequenced to confirm the species-level diagnosis (4). The sequence data of the 558-bp amplicon was deposited in GenBank (Accession No. KJ477016.1) and nBLAST search showed 99% homology with Diaporthe citri (teleomorph) strain 199.39 (KC343051.1). P. citri is known for its association with melanose disease of citrus in India, the United States, and abroad. P. citri also causes stem end rot of citrus, which leads to yield loss and reduction in fruit quality (1,2). Dieback disease is of serious concern for lemon growers as it affects the overall productivity level of the tree. To the best of our knowledge, this is the first report of P. citri causing dieback of lemon in India. References: (1) I. H. Fischer et al. Sci. Agric. (Piracicaba). 66:210, 2009. (2) S. N. Mondal et al. Plant Dis. 91:387, 2007. (3) S. P. Raychaudhuri. Proc. Int. Soc. Citriculture 1:461, 1981. (4) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA, 1990.

Download Full-text

Sporulation Capacity and Longevity of Puccinia horiana Teliospores in Infected Chrysanthemum Leaves

Plant Health Progress ◽

10.1094/php-2013-0823-01-rs ◽

2013 ◽

Vol 14 (1) ◽

pp. 11 ◽

Cited By ~ 3

Author(s):

Morris R. Bonde ◽

Cristi L. Palmer ◽

Douglas G. Luster ◽

Susan E. Nester ◽

Jason M. Revell ◽

...

Keyword(s):

United States ◽

Fungal Pathogen ◽

Local Environment ◽

The United States ◽

First Report ◽

White Rust ◽

Teliospore Germination ◽

Sporulation Capacity ◽

Leaf Necrosis ◽

Puccinia Horiana

Puccinia horiana Henn., a quarantine-significant fungal pathogen and causal agent of chrysanthemum white rust (CWR), was first discovered in the United States in 1977 and later believed to have been eradicated. Recently, however, the disease has sporadically reappeared in the northeastern US. Possible explanations for the reappearance include survival of the pathogen in the local environment, and reintroduction from other locations. To determine the possibility that the pathogen might be overwintering in the field, we undertook the study described here. Results from the study showed that P. horiana teliospores, imbedded in infected leaves, were capable of sporulating 2 weeks after inoculation, and this capacity continued until the leaf became necrotic and desiccated. This is the first report of the extreme susceptibility of P. horiana teliospores to leaf necrosis and desiccation and suggests that field infections following winter are unlikely to originate from teliospores. Teliospore germination on excised leaves was shown to be inhibited by light. Accepted for publication 3 April 2013. Published 23 August 2013.

Download Full-text

First report of leaf spot disease caused by Stemphylium eturmiunum on garlic in Korea.

Plant Disease ◽

10.1094/pdis-03-21-0674-pdn ◽

2021 ◽

Author(s):

Walftor Dumin ◽

Mi-Jeong Park ◽

You-Kyoung Han ◽

Yeong-Seok Bae ◽

Jong-Han Park ◽

...

Keyword(s):

Leaf Spot ◽

Allium Sativum ◽

Morphological Characteristics ◽

Fungal Isolate ◽

Causal Agent ◽

Leaf Spot Disease ◽

Pathogenicity Test ◽

First Report ◽

Spot Disease ◽

Intact Leaves

Garlic (Allium sativum L. cv.namdo) is one of the most popular vegetables grown in Korea due to its high demand from the food industry. However, garlic is susceptible to a wide range of pest infestations and diseases that cause a significant decrease in garlic production, locally and globally (Schwartz and Mohan 2008). In early 2019, the occurrence of leaf blight disease was found spreading in garlic cultivation areas around Jeonnam (34.9671107, 126.4531825) province, Korea. Disease occurrence was estimated to affect 20% of the garlic plants and resulted in up to a 3-5% decrease in its total production. At the early stage of infection, disease symptoms were manifested as small, white-greyish spots with the occurrence of apical necrosis on garlic leaves. This necrosis was observed to enlarge, producing a water-soaked lesion before turning into a black-violet due to the formation of conidia. As the disease progressed, the infected leaves wilted, and the whole garlic plants eventually died. To identify the causal agent, symptomatic tissues (brown dried water-soak lesion) were excised, surface sterilized with 1% NaOCl and placed on the Potato Dextrose Agar (PDA) followed by incubation at 25°C in the dark for 5 days. Among ten fungal isolates obtained, four were selected for further analyses. On PDA, fungal colonies were initially greyish white in colour but gradually turned to yellowish-brown after 15 days due to the formation of yellow pigments. Conidia were muriform, brown in colour, oblong (almost round) with an average size of 18 – 22 × 16 – 20 μm (n = 50) and possessed 6 - 8 transverse septa. Fungal mycelia were branched, septate, and with smooth-walled hyphae. Morphological characteristics described above were consistent with the morphology of Stemphylium eturmiunum as reported by Simmons (Simmons, 2001). For molecular identification, molecular markers i.e. internal transcribed spacer (ITS) and calmodulin (cmdA) genes from the selected isolates were amplified and sequenced (White et al., 1990; Carbone and Kohn 1999). Alignment analysis shows that ITS and cmdA genes sequence is 100% identical among the four selected isolates. Therefore, representative isolate i.e. NIHHS 19-142 (KCTC56750) was selected for further analysis. BLASTN analysis showed that ITS (MW800165) and cmdA (LC601938) sequences of the representative isolates were 100% identical (523/523 bp and 410/410 bp) to the reference genes in Stemphylium eturmiunum isolated from Allium sativum in India (KU850545, KU850835) respectively (Woudenberg et al. 2017). Phylogenetic analysis of the concatenated sequence of ITS and cmdA genes confirmed NIHHS 19-142 isolates is Stemphylium eturmiunum. Pathogenicity test was performed using fungal isolate representative, NIHHS 19-142. Conidia suspension (1 × 106 conidia/µL) of the fungal isolate was inoculated on intact garlic leaves (two leaves from ten different individual plants were inoculated) and bulbs (ten bulbs were used) respectively. Inoculation on intact leaves was performed at NIHHS trial farm whereas inoculated bulbs were kept in the closed container to maintain humidity above 90% and incubated in the incubator chamber at 25°C. Result show that the formation of water-soaked symptoms at the inoculated site was observed at 14 dpi on intact leaves whereas 11 dpi on bulbs. As a control, conidia suspension was replaced with sterile water and the result shows no symptoms were observed on the control leaves and bulbs respectively. Re-identification of fungal colonies from symptomatic leaf and bulb was attempted. Result showed that the morphological characteristics and molecular marker sequences of the three colonies selected were identical to the original isolates thus fulfilled Koch’s postulates. Early identification of Stemphylium eturmiunum as a causal agent to leaf spot disease is crucial information to employ effective disease management strategies or agrochemical applications to control disease outbreaks in the field. Although Stemphylium eturmiunum has been reported to cause leaf spot of garlic disease in China, France and India (Woudenberg et al. 2017), to our knowledge, this is the first report of causing leaf spot disease on garlic in Korea.

Download Full-text

First Report of Cobweb Disease Caused by Cladobotryum mycophilum on the Edible Mushroom Pleurotus eryngii in Korea

Plant Disease ◽

10.1094/pdis-01-12-0015-pdn ◽

2012 ◽

Vol 96 (9) ◽

pp. 1374-1374 ◽

Cited By ~ 10

Author(s):

M. K. Kim ◽

Y. H. Lee ◽

K. M. Cho ◽

J. Y. Lee

Keyword(s):

Fungal Pathogen ◽

Natural Infection ◽

Morphological Characteristics ◽

Edible Mushroom ◽

Pleurotus Eryngii ◽

Pathogenicity Test ◽

Distilled Water ◽

First Report ◽

Cobweb Disease ◽

Fungal Mycelia

Pleurotus eryngii is one of the most commercially important mushrooms in Korea. In May 2009, unusual symptoms were observed in P. eryngii grown in mushroom farms in Changnyeong and Hapcheon, in Gyeong-nam Province, Korea. One of the main symptoms was cobweb-like growth of fungal mycelia over the mushroom surface. Colonies on the surface rapidly overwhelmed the mushrooms, which turned pale brown or yellow. Mushrooms eventually turned dark brown and became rotten. Colonies of the isolates on potato dextrose agar (PDA) were yellowish, and a reddish or orange color was evident in the agar. The colonies grew 20 to 30 mm per day on PDA. Large spores with a single septum were produced on vertically branched conidiophores bearing two to four, mostly three to four, sporogenous cells, ranging from 17.2 to 20.5 μm long and 8.0 to 10.2 μm thick. The shape of the conidia was ellipsoid and obovoid. These morphological characteristics are consistent with descriptions of Cladobotryum mycophilum, a causal agent of cobweb disease in Agaricus bisporus (1,4). To identify the isolated fungal pathogen, the ITS region was amplified with ITS1 and ITS4 primers and sequenced. The sequence data from the isolate was deposited in GenBank (Accession No. JF693809). A BLAST search showed that the isolated strain belonged to a species of Cladobotryum. The highest similarity (99.5%) was to the ITS sequence of C. mycophilum (teleomorph Hypomyces odoratus) (GenBank Accession Nos. JF505112 and Y17096) (3,4). The strain that was tested for pathogenicity was grown on PDA at 25°C for 72 h. The inoculum was prepared by flooding the agar surface with 10 ml of sterilized double distilled water and scraping it with a spatula. The resulting spore suspension was filtered through three layers of cheesecloth. Conidial concentration was adjusted with a hemacytometer to 1 × 106 conidia ml–1. A conidia suspension was inoculated onto each of several stages of mushroom cultivation with a pipette. The control was spotted with double distilled water. In the case of infection during the inoculation and spawn running stages, the fungal mycelia colonized the media and hampered development of the mycelium of P. eryngii. In the regeneration and primordia formation stages of the host, the mycelium of the pathogen covered the surface of the plastic bottle containing the substrates and developed many spores. In the growing and harvesting stages, the surface of mushroom was overwhelmed by the mycelium of the fungal pathogen and turned pale or dark brown, accompanied by cracking of the stipe surface and finally rotting with a foul odor. These symptoms were similar to the observation from natural infection. The symptoms of the cobweb-like disease in A. bisporus (1,2) were observed within 5 to 7 days of inoculation with conidia suspensions of C. mycophilum. Fungi isolated from inoculated mushrooms were shown to be identical, based on phenotypic characteristic, to the inoculated strain used in these pathogenicity tests. No symptoms were observed on controls. To our knowledge, this is the first report on the occurrence of C. mycophilum on the edible mushroom P. eryngii in Korea. Based on the pathogenicity test results, the pathogen could attack P. eryngii in any cultivation stage, making it a potentially serious fungal pathogen in P. eryngii. References: (1) C. G. Back et al. J. Gen. Plant Pathol. 76:232, 2010. (2) R. H. Gaze. Mushroom J. 546:23, 1995. (3) F. J. Gea et al. Plant Dis. 95:1030, 2011. (4) H. M. Grogan and R. H. Gaze. Mycol. Res. 104:357, 2000.

Download Full-text

First Report of Fusarium proliferatum Causing Rot of Garlic Bulbs (Allium sativum) in India

Plant Disease ◽

10.1094/pdis-08-11-0649 ◽

2012 ◽

Vol 96 (2) ◽

pp. 290-290 ◽

Cited By ~ 9

Author(s):

N. Ravi Sankar ◽

Gundala Prasad Babu

Keyword(s):

Sodium Hypochlorite ◽

Allium Sativum ◽

Morphological Characteristics ◽

Aerial Mycelium ◽

Its Region ◽

Fusarium Proliferatum ◽

Distilled Water ◽

Sequence Comparisons ◽

First Report ◽

Plant Pathol

In September 2009, diseased garlic bulbs (Allium sativum L. cv. Yamuna Safed) were received from producers and exporters in Hyderabad, Andra Pradesh, India. From 2009 to 2010, similar symptoms were observed on stored garlic bulbs (cvs. Yamuna Safed and Agrifound White) in Chittoor, Kadapa, and Hyderabad districts. In some locations, approximately 60% of the garlic bulbs were affected. At first, infected bulbs showed water-soaked, brown spots and then the disease progressed as small, slightly depressed, tan lesions. A total of 120 diseased samples were collected from all localities. Infected tissues were surface sterilized in 1% sodium hypochlorite for 2 min, rinsed three times in sterile distilled water, plated on potato dextrose agar (PDA), and incubated at 25°C for 7 days. Resultant fungal colonies were fast growing with white aerial mycelium and violet to dark pigments. Hyphae were septate and hyaline. Conidiophores were short, simple, or branched. Microconidia were abundant, single celled, oval or club shaped, measuring 4.5 to 10.5 × 1.3 to 2.5 μm, and borne in chains from both mono-and polyphialides. Macroconidia were not produced. On the basis of morphological characteristics, the pathogen was identified as Fusarium proliferatum (Matsushima) Nirenberg (2). Identification was confirmed by amplification of the internal transcribed spacer (ITS) region. Genomic DNA was extracted from pure cultures of an isolate, and the ITS region was amplified using the ITS4/5 primer pair. PCR amplicons of approximately 574 bp were obtained from isolates, and sequence comparisons with GenBank showed 99% similarity with F. proliferatum (Accession No. FN868470.1). Sequence from this study was submitted to GenBank nucleotide database (Accession No. AB646795). Pathogenicity tests were conducted with three isolates of the fungus following the method of Dugan et al. (1). Each assay with an isolate consisted of 10 garlic cloves disinfected in 1% sodium hypochlorite for 45 s, rinsed with sterile distilled water, and injured to a depth of 4 mm with a sterile 1-mm-diameter probe. The wounds were filled with PDA colonized by the appropriate isolate from a 5-day-old culture. Ten cloves for each tested isolate received sterile PDA as a control. The cloves were incubated at 25°C for 5 weeks; tests were repeated once. After 17 days, rot symptoms similar to the original symptoms developed on all inoculated cloves and F. proliferatum was consistently reisolated from symptomatic tissue, fulfilling Koch's postulates. No fungi were recovered from control cloves. F. proliferatum has been reported on garlic in the northwestern United States (1), Serbia (4), and Spain (3). To our knowledge, this is the first report of F. proliferatum causing rot disease on garlic bulbs in India. References: (1) F. M. Dugan et al. Plant Pathol. 52:426, 2003. (2) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Publishing, Oxford, UK, 2006. (3) D. Palmero et al. Plant Dis. 94:277, 2010. (4) S. Stankovic et al. Eur. J. Plant Pathol. 48:165, 2007.

Download Full-text

First Report of Sclerotium rolfsii on Catharanthus roseus

Plant Disease ◽

10.1094/pdis.2000.84.2.200d ◽

2000 ◽

Vol 84 (2) ◽

pp. 200-200

Author(s):

G. E. Holcomb

Keyword(s):

Catharanthus Roseus ◽

Fungal Pathogen ◽

Baton Rouge ◽

Sclerotium Rolfsii ◽

The United States ◽

Madagascar Periwinkle ◽

Basal Stem Rot ◽

First Report ◽

Pathogenicity Tests ◽

Stem Necrosis

Wilt, blight, and stem necrosis were observed on Catharanthus roseus (L.) G. Don ‘Mediterranean Deep Rose’ (MDR) plants (Madagascar or rose periwinkle) in August 1999 at Burden Research Plantation in Baton Rouge, LA. MDR was the only prostrate-form cultivar and the only cultivar of 11 that was diseased. Twelve of twenty-four plants of cv. MDR were killed in the trial planting. White mycelia and small (1 mm diameter) light brown sclerotia were present at the base of infected plants. The suspect fungus was isolated consistently on acidified water agar and maintained on acidified potato dextrose agar (APDA). Pathogenicity tests were done by pipetting 1 ml of blended inoculum (contents of one 7-day-old plate culture grown on APDA in 100 ml of deionized water) at the base of nine 15-cm-tall Madagascar periwinkle plants. Inoculated and noninoculated plants were held in a dew chamber for 3 days at 28°C and placed in a greenhouse where temperatures ranged between 25 and 31°C. All inoculated plants showed wilt, blight, and basal stem rot after 3 days and were dead after 10 days. Noninoculated plants remained symptomless. The fungal pathogen was identified as Sclerotium rolfsii Sacc. and was reisolated from inoculated plants. The fungus was previously reported on Lochnera rosea (L.) Rchb. (=C. roseus) from Taiwan (1). This is the first report of the occurrence of S. rolfsii on Madagascar periwinkle in the United States. Reference: (1) K. Goto. Trans. Nat. Hist. Soc. Formosa 23:37, 1933.

Download Full-text

First report of Orobanche cernua parasitism on Allium sativum in Banda district of Uttar Pradesh, India

Indian Phytopathology ◽

10.1007/s42360-018-0057-4 ◽

2018 ◽

Vol 71 (3) ◽

pp. 463-464 ◽

Cited By ~ 2

Author(s):

Gulwaiz Akhter ◽

Tabreiz Ahmad Khan

Keyword(s):

Allium Sativum ◽

Uttar Pradesh ◽

First Report

Download Full-text

Effect of Two Allexivirus Isolates on Garlic Yield

Plant Disease ◽

10.1094/pd-90-0898 ◽

2006 ◽

Vol 90 (7) ◽

pp. 898-904 ◽

Cited By ~ 14

Author(s):

E. E. Cafrune ◽

M. C. Perotto ◽

V. C. Conci

Keyword(s):

Allium Sativum ◽

Negative Control ◽

Yield Losses ◽

Assay Condition ◽

First Report ◽

Virus Complex ◽

Significant Yield ◽

Virus C ◽

Garlic Virus ◽

Assay Conditions

Garlic (Allium sativum) is infected by numerous viruses forming a viral-complex, which is widely distributed in the garlic production regions of Argentina. This work is the first report of the effect of two Allexivirus isolates, Garlic virus A (GarV-A) and Garlic virus C (GarV-C), on garlic yield. Garlic cvs. Morado-INTA and Blanco-IFFIVE were used in the experiments, and four treatments were evaluated: plants inoculated with GarV-A only, GarV-C only, virus-free plants (negative control), and plants infected with the virus-complex. Assays were performed in anti-aphid cages and in the field during 2002 and 2003. GarV-A caused significant reductions in bulb weight (14 to 32%) and diameter (6 to 11%) compared with the negative control in the two cultivars under both assay conditions. GarV-C caused less damage than GarV-A (15% in weight and 5% in diameter) with respect to the negative control in cv. Blanco-IFFIVE, and did not produce significant yield losses in cv. Morado-INTA in either year or under either assay condition.

Download Full-text

First Report of Fusarium wilt disease on Watermelon Caused by Fusarium oxysporum f. sp. niveum (FON) in Malaysia

Plant Disease ◽

10.1094/pdis-04-21-0780-pdn ◽

2021 ◽

Author(s):

Muhammad Ziaur Rahman ◽

Khairulmazmi Ahmad ◽

Yasmeen Siddiqui ◽

Norsazilawati Saad ◽

Tan Geok Hun ◽

...

Keyword(s):

Fusarium Oxysporum ◽

Fusarium Wilt ◽

Cover Crops ◽

Fungal Pathogen ◽

Disease Incidence ◽

Wilt Disease ◽

Likelihood Method ◽

Distilled Water ◽

First Report ◽

Fusarium Wilt Disease

Fusarium wilt disease incited by Fusarium oxysporum f. sp. niveum (FON) is the utmost devastating soil-inhabiting fungal pathogen limiting watermelon (Citrullus lanatus) production in Malaysia and globally. The field disease survey of fusarium wilt was carried out during December 2019 and November 2020, in three major production areas (3 farmer fields per location) in Peninsular Malaysia namely, Mersing, Serdang and Kuantan and disease incidence of 30 and 45%, was recorded for each year, respectively. Infected watermelon plants showed symptoms such as vascular discoloration, brown necrotic lesions to the soil line or the crown, one-sided wilt of a plant, or a runner or the whole plant. Infected root and stem tissues, 1-2 cm pieces were surface sterilized with 0.6% NaOCl for 1 minute followed by double washing with sterile water. The disinfected tissues were air-dried and transferred onto semi-selective Komada’s medium (Komada 1975) and incubated for 5 days. The fungal colonies produced were placed on potato dextrose agar (PDA) to attain a pure culture and incubated at 25±2℃ for 15 days. The pure fungal colony was flat, round and light purple in color. Macroconidia were straight to slightly curved, 18.56-42.22 µm in length, 2.69-4.08 µm width, predominantly 3 septate and formed in sporodochia. Microconidia measured 6.16-10.86 µm in length and 2.49-3.83 µm in width, kidney-shaped, aseptate and were formed on short monophialides in false-heads. Chlamydospores were single or in pairs with smooth or rough walls, found both terminally or intercalary. To confirm their pathogenicity, two-week-old watermelon seedlings (cv. NEW BEAUTY) were dipped into spore suspension (1 ˟ 106 spores/ml) of representative isolates of JO20 (Mersing), UPM4 (Serdang) and KU41 (Kuantan) for 30 second and then moved into 10 cm diameter plastic pots containing 300 g sterilized soil mix. Disease symptoms were assessed weekly for one month. Control seedlings were immersed in sterile distilled water before transplanting. The inoculated seedlings showed typical Fusarium wilt symptoms like yellowing, stunted growth, and wilting, which is similar to the farmer field infected plants. However, the seedlings inoculated by sterile distilled water remained asymptomatic. The pathogen was successfully re-isolated from the infected seedlings onto Komada’s medium, fulfilling the Koch’s postulate. For the PCR amplification, primers EF-1 and EF-2 were used to amplify the tef1-α region. A Blastn analysis of the tef1-α sequences of the isolates JO20 (accession nos. MW315902), UPM4 (MW839560) and KU41 (MW839562) showed 100% similarity; with e-value of zero, to the reference sequences of F. oxysporum isolate FJAT-31690 (MN507110) and F. oxysporum f. sp. niveum isolate FON2 790-2 (MN057702). In Fusarium MLST database, isolates JO20, UPM4 and KU41 revealed 100% identity with the reference isolate of NRRL 22518 (accession no. FJ985265). Though isolate FJ985265 belongs to the f. sp. melonis, earlier findings had revealed Fusarium oxysporum f. sp. are naturally polyphyletic and making clusters with diverse groups of the Fusarium oxysporum species complex (O’Donnell et al. 2015). The isolates JO20, UPM4 and KU41 were identified as F. oxysporum f. sp. niveum based on the aligned sequences of tef1-α and molecular phylogenetic exploration by the maximum likelihood method. To the best of our knowledge, this is the first report of F. oxysporum f. sp. niveum as a causative pathogen of Fusarium wilt disease of watermelon in Malaysia. Malaysia enables to export watermelon all-year-round in different countries like Singapore, Hong-Kong, The United Arab Emirates (UAE), and Netherlands. The outburst of this destructive soil-borne fungal pathogen could cause hindrance to watermelon cultivation in Malaysia. Thus, growers need to choice multiple management tactics such as resistant varieties, cultural practices (soil amendments and solarization), grafting, cover crops and fungicide application to control this new pathogen.

Download Full-text

First Report of Web Blight on Verbena Caused by Rhizoctonia solani

Plant Disease ◽

10.1094/pdis.2000.84.4.492a ◽

2000 ◽

Vol 84 (4) ◽

pp. 492-492 ◽

Cited By ~ 2

Author(s):

G. E. Holcomb ◽

D. E. Carling

Keyword(s):

Rhizoctonia Solani ◽

Fungal Pathogen ◽

Baton Rouge ◽

Anastomosis Group ◽

First Report ◽

Foliage Blight ◽

Pathogenicity Tests ◽

Stem Lesions ◽

Web Blight ◽

Branch Death

Web blight was observed on verbena (Verbena × hybrida) during July 1999 in a cultivar trial planting at Burden Research Plantation in Baton Rouge, LA. Foliage blight, stem lesions, and branch death were common symptoms on 12 of 24 cultivars in the trial. Plant death occurred in cvs. Babylon Florena (one of four plants), Purple Princess (two of four plants), and Taylortown Red (two of four plants). Isolations from infected leaves and stems on acidified water agar consistently yielded a fungus with the mycelial and cultural characteristics of Rhizoctonia solani. Pathogenicity tests were carried out by placing 5-day-old fungal mycelial plugs, grown on acidified potato dextrose agar, at the base of healthy verbena stems and holding plants in a dew chamber at 26°C. After 3 days, foliage blight and stem lesions appeared on inoculated plants, and plants were moved to a greenhouse where temperatures ranged from 23 to 32°C. Seven of nine inoculated plants died after 7 days; noninoculated plants remained healthy. The fungal pathogen was reisolated from all inoculated plants. The fungus was identified as R. solani anastomosis group (AG)-1 IB based on multinucleate condition, type of sclerotia produced, and ability to anastomose with R. solani tester isolates of AG-1 IB. This is the first report of web blight on verbena.

Download Full-text