An Outbreak of Gummosis of Mango Trees Caused by Lasiodiplodia theobromae in Guangxi, South China

Mango (Mangifera indica L.) is an economically important fruit in southern provinces of China. In May 2012, field surveys including 2,250 mango trees were done in nine orchards of five different counties in Guangxi Province. An outbreak of gummosis was observed in the province involving over 30,000 ha with an average of 50% disease incidence (DI) and a maximum of 70% in some orchards. Until then, gummosis had been considered a common but not serious disease. In 2012, high temperatures in April and extensive rain in May favored increased disease development. Infected plants showed abundant gum secretion from branches, stems, and main trunks. Some branches died from the disease. During the early stages of infection, branches or stems turned brown followed by xylem necrosis and exudation of a milky sap. The sap turned yellow and finally formed amber gum within several days. Initially, the gum appeared as small droplets, increasing in number, and covering most of the branches and the trunk with bark cracking under severe conditions. On potato dextrose agar (PDA), isolates with similar morphology were consistently recovered from symptomatic plant tissues after surface sterilization in 75% ethanol for 30 seconds and then in 0.1% mercuric chloride for 1 min. Five single-spore isolates from five different locations in Guangxi Province were used to evaluate characteristics of the pathogen. On PDA, cultures were gray with an irregularly distributed, fast-growing, and fluffy aerial mycelium, showing a dark underside as the colony changed from greenish to black after 5 days at 28°C. After 1 month, cultures produced globose pycnidia. Conidia were elliptical and hyaline when immature, becoming dark brown and one-septate, longitudinally striate when mature, and ranged from 20.0 to 28.0 × 10.5 to 16.0 μm (average 23.3 × 13.7 μm). Paraphyses produced within the tissues of pycnidia were hyaline, cylindrical, nonseptate, and up to 61 μm long. The fungus was identified as Lasiodiplodia theobromae (Pat.) Griffon & Maubl. (=Botryosphaeria rhodina (Cooke) Arx) based on morphological and cultural characteristics (1,2). The rDNA internal transcribed spacer region of one isolate showed 100% identity to L. theobromae (GenBank HM346876.2) and was deposited in GenBank (JX982240). Pathogenicity of the five isolates was tested in the field on healthy tissues in June 2012. Five green twigs and five 3-year-old branches were used. Three wounds were made on each twig or branch with a sterilized needle. Mycelial plugs were placed on wounds and covered with Parafilm. Uncolonized PDA plugs were used as controls. Two weeks later, typical brown lesions were observed on inoculated branches, and gum exuded from infected wounds. No symptoms were seen on the controls. Koch's postulates were fulfilled by reisolation of L. theobromae from diseased branches. L. theobromae is well documented as a pathogen of mango. In China, the disease was observed in the 1990s in Hainan Province, and the causal agents were identified as L. theobromae and Colletotrichum gloeosporioides Penz. & Sacc based on morphological observation (3). To our knowledge, this is the most severe outbreak reported from China. References: (1) V. S. de Oliveira Costa et al. Eur. J. Plant Pathol. 127:509, 2010. (2) F. Wang et al. Plant Dis. 95:1378, 2011. (3) Q. C. Xiao et al. Tropical Crops Research (in Chinese) 2:25, 1995.

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First Report of Lasiodiplodia pseudotheobromae Causing Stem End Rot of Mango Fruit in Pakistan

Plant Disease ◽

10.1094/pdis-01-21-0099-pdn ◽

2021 ◽

Author(s):

Muhammad Waqar Alam ◽

Arif Malik ◽

Abdul Rehman ◽

Mubeen Sarwar ◽

Tahir Shafeeq ◽

...

Keyword(s):

Disease Incidence ◽

Mangifera Indica ◽

Morphological Characteristics ◽

Aerial Mycelium ◽

Postharvest Disease ◽

Single Spore ◽

Mango Fruit ◽

First Report ◽

Field Samples ◽

Rot Disease

Mango (Mangifera indica L.) is considered a desirable fruit in international markets and is grown throughout tropical and sub-tropical countries around the world (Alemu, 2014). Stem end rot is the most damaging and complex postharvest disease of mango, resulting in losses of up to 40% in Pakistan, which is the leading producer and exporter (Alam et al. 2017). A field survey was conducted in June of 2017 and 2018 in the Rahim Yar Khan and Multan- major mango producing regions of Punjab Province. After mature but unripe mango fruit (cv. Samar Bahisht Chaunsa) were stored at 12°C for 2 weeks to permit ripening, water-soaked, dark brown to purplish black decay began to appear around the stem end portion. The decay gradually enlarged and covered the whole fruit after 7 days. Disease incidence was estimated at 30%. Small pieces (3 to 4 mm2) from the periphery of 15 diseased fruit were surface disinfected with 1% sodium hypochlorite for 2 min, rinsed three times in sterilized distilled water, air dried, and then placed aseptically onto potato dextrose agar (PDA) medium and incubated at 25°C under a 12-h light/dark photoperiod for 7 days. Twelve single-spore isolates with similar morphology were isolated from the infected tissues. Initially the fungus produced thick, fluffy and greyish-white aerial mycelium, that later turned into dark gray colonies. Conidia were unicellular, ellipsoidal, and initially hyaline, but with age became dark brown and developed a central septum. Conidia measured 24.5 to 31.5 × 11.4 to 15.7 µm (n = 60). Conidiophores were inflated at their base with one diaphragm which reduced to conidiogenous cells. Conidiogenous cells were hyaline and cylindrical. On the basis of morphological characteristics, the fungus was tentatively identified as Lasiodiplodia sp., a member of the family Botryosphaeriaceae (Alves et al. 2008). For molecular identification, genomic DNA was extracted from mycelium following the CTAB method. The internal transcribed spacer (ITS) region of rDNA and translation elongation factor 1-alpha (TEF1-α) gene were amplified using ITS1/ITS4 (White et al. 1990) and EF1-728F/EF1-986R primer sets (Carbone and Kohn 1999), respectively. BLASTn searches of sequences revealed 99% to 100% identity with the reference sequences of various Lasiodiplodia pseudotheobromae isolates (GenBank accession nos. MH057189 for ITS; MN638768 for TEF-1a). The sequences were deposited in GenBank (accession nos. MW439318, MW433883 for ITS; and MW463346, MW463347 for TEF-1a). To fulfill Koch’s postulates, a suspension of 105 conidia/ml from a 7-day-old culture of L. pseudotheobromae was used to inoculate fully mature but unripe mango fruit (cv. Samar Bahisht Chaunsa). Fruit were pricked with a sterilized needle to a depth of 4 mm at the stem end portion, injected with 50 μl of the prepared spore suspension (Awa et al. 2012), and stored at 12°C for 3 weeks under 70 to 80% RH. Twenty mango fruit were inoculated, and 10 were inoculated with sterile water only. After 15 days, most fruit showed typical symptoms at the stem end. Reisolations from symptomatic fruit following the procedures described above for isolating and identifying the fungal cultures from infected field samples, consistently yielded a fungus identical to L. pseudotheobromae. Control fruit remained disease-free. Although L. pseudotheobromae was previously reported on several forest and fruit trees (Alves et al. 2008; Awan et al. 2016), this is the first report of the pathogen causing stem end rot disease of mango in Pakistan. This report is important for the new studies aiming at management of stem end rot disease of mango caused by L. pseudotheobromae in Pakistan.

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Boeremia exigua Causes Leaf Spot of Walnut Trees (Juglans regia) in China

Plant Disease ◽

10.1094/pdis-10-21-2304-pdn ◽

2021 ◽

Author(s):

Fanfan Wang ◽

Chunyao Dun ◽

Tao Tang ◽

XiaoLiang Guo ◽

Yuanyuan Duan ◽

...

Keyword(s):

Juglans Regia ◽

Management Strategies ◽

Morphological Characteristics ◽

Aerial Mycelium ◽

Pathogenicity Test ◽

Internal Transcribed Spacer Region ◽

Beta Tubulin ◽

Surface Sterilization ◽

The World ◽

Necrotic Spots

Walnuts are an important perennial nut crop widely cultivated in China, which are rich in protein, carbohydrate, renieratene, and other beneficial nutrients. China is the largest producer of walnuts in the world, with the largest planting area and output. At the end of April 2020, several unknown necrotic spots on leaves of walnut trees were observed in a Juglans regia field located in Sancha Town, Enshi, China (30°28′N, 109°64′E). Initially, lesions were black, small, sunken, and turning to yellowish-brown, irregular, well surrounded by brown margins. Severely, leaf spots coalesced and resulted in withered and abscised. In order to identify the pathogen, infected leaves were collected. Sections of leaves were aseptically excised from the margins of necrotic spots following surface sterilization and placed on potato dextrose agar (PDA) at 28℃. After 4 days, fungal isolates were obtained and purified by hyphal tip isolation. The isolates looked morphologically similar, producing colonies that appeared hyphae with dark grey, lobed margins, and aerial mycelium with white to light gray. After 15 days of incubation, subglobose, dark brown pycnidia (100-176 μm in wide, 75-95 μm in length) were formed with an orifice in the center, producing conidia. Conidia (3.5 to 9.0 × 1.6 to 4.5 μm) were oval to round, aseptate, occasionally 1-septate. These morphological characteristics lead to the conclusion that the isolates may be identified as Phoma sp. (Boerema et al. 1976). A single isolate was randomly selected and designated for further verification. To confirm the identity, the internal transcribed spacer region (ITS), actin (ACT) and beta-tubulin genes were amplified and sequenced ITS1/ITS4, ACT-512F/ACT-783R, and Bt2a/Bt2b, respectively (White et al. 1990, Groenewald et al. 2013). BLAST analysis of the ITS 505-bp sequence (GenBank accession no. MW282913), actin 269-bp sequence (GenBank accession no. MW201958), and beta-tubulin 347-bp sequence (GenBank accession no. MW273782) showed ≥99% homology with the sequences of B. exigua available in GenBank (GenBank accession no. AB454232, LT158234, and KR010463, respectively). Base on the above results, the strain HTY2 was identified as B. exigua. Pathogenicity was tested. Walnut plants were spray-inoculated with a spore suspension (5 x 105 CFU/mL). Controls were inoculated as described above except that sterile distilled water in the dark at 25 ℃. After seven days, lesions were evident at inoculation points, and equivalent to those observed in field were observed. Control leaves remained symptomless. The pathogenicity test was repeated thrice and the results were the same, fulfilling the Koch’s postulates. The pathogen has been reported on various plants around the world, causing a series of symptoms. Infected plants rarely died, but the presence of lesions decreased their fruit quality and yield. Previous identification of the disease is essential in formulating management strategies.

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Identification and Characterization of Colletotrichum Species Associated with Mango Anthracnose in Guangxi, China

Plant Disease ◽

10.1094/pdis-09-17-1516-re ◽

2018 ◽

Vol 102 (7) ◽

pp. 1283-1289 ◽

Cited By ~ 19

Author(s):

Jianyou Mo ◽

Guang Zhao ◽

Qili Li ◽

Ghulam S. Solangi ◽

Lihua Tang ◽

...

Keyword(s):

Southern China ◽

Mangifera Indica ◽

Guangxi Province ◽

Internal Transcribed Spacer Region ◽

Colletotrichum Species ◽

Mango Leaves ◽

Genomic Regions ◽

Identification And Characterization

Mango (Mangifera indica) is widely grown across southern China, especially in the provinces of Guangxi, Hainan, Yunnan, Sichuan, and Taiwan. Guangxi itself has over 86,667 ha of mango production. The purpose of this study was to identify Colletotrichum species associated with mango in different parts of Guangxi and examine their pathogenicity on leaves and fruits of mango in vitro. Diseased leaves were collected from 25 mango orchards in different areas of Guangxi province. Sixty-five isolates were obtained from mango leaves with anthracnose symptoms, and these were further characterized based on morphology and DNA sequencing. Twenty-nine isolates from different areas were selected for sequencing and analyses of the internal transcribed spacer region, glyceraldehyde-3-phosphate dehydrogenase, partial actin, β-tubulin, and chitin synthase genomic regions. The most common fungal isolates were these three species: Colletotrichum asianum, C. fructicola, and C. siamense. C. asianum was the most common and widely distributed in Guangxi (51.7%), followed by C. fructicola (37.9%) and C. siamense (10.2%), both found in Tiandong, Tianyang, and Wuming counties. There was no evidence of geographical specialization of the different species. Pathogenicity assays showed that all isolates were pathogenic to mango leaves and fruit (cultivar Tainong). No relationship was found between origin of isolates and their virulence. This is the first description of C. asianum, C. fructicola, and C. siamense as causal agents of mango leaf anthracnose from Guangxi province, China.

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First Report of Boeremia Blight Caused by Boeremia exigua var. exigua on Pyrethrum in Australia

Plant Disease ◽

10.1094/pdis-05-11-0424 ◽

2011 ◽

Vol 95 (11) ◽

pp. 1478-1478 ◽

Cited By ~ 5

Author(s):

S. J. Jones ◽

F. S. Hay ◽

T. C. Harrington ◽

S. J. Pethybridge

Keyword(s):

Disease Incidence ◽

Elongation Factor ◽

Its Region ◽

Tween 20 ◽

Width Ratio ◽

Malt Extract ◽

Base Pairs ◽

Internal Transcribed Spacer Region ◽

First Report ◽

Surface Sterilization

Pyrethrum (Tanacetum cinerariifolium) is produced for extraction of insecticidal compounds from the flower achenes. In 2004 and 2006, isolations from necrotic lesions on stems and leaves in three fields in northern Tasmania, Australia yielded four unidentified fungal isolates. Leaf lesions were medium brown and circular (2 to 4 mm in diameter) or irregular in shape (2 to 5 mm long). Stem lesions were irregular, necrotic spots, 5 to 15 mm below the flower peduncle, medium brown, 2 to 4 mm long, and 1 to 2 mm wide. Isolations were conducted on water agar following surface sterilization. Isolates were identified by colony characteristics and the presence of metabolite ‘E’ (1). On oatmeal agar (OA), colonies had irregular margins, were greenish olivaceous-to-olivaceous gray with sparse, white, floccose, aerial mycelia. On malt extract agar (MEA), cultures were variable in color with olivaceous black centers with soft, dense, aerial mycelia. Conidia were hyaline, ellipsoidal to oblong, mainly aseptate, but occasionally 1-septate with dimensions ranging from 2.5 to 7.5 × 1.8 to 3.8 μm (length/width ratio = 1.7 to 2.1). All isolates had moderate reactions to the NaOH test for metabolite ‘E’. DNA was extracted from all four isolates with a DNeasy Plant Mini Kit (QIAGEN Inc., Valencia, CA). For identification, the internal transcribed spacer region (ITS1, 5.8s, and ITS2) and part of the translation elongation factor (TEF) region were amplified and sequenced. Primers ITS1 and ITS4 (2) were used for the ITS region and primers EFCF1 (5′-AGTGCGGTGGTATCGACAAG) and EFCF6 (3′-CATGTCACGGACGGCGAAAC) were used for the TEF. Amplicons were sequenced in both directions and consensus sequences assembled. The ITS sequence was 100% identical to Boeremia exigua var. exigua (GenBank Accession No. GU237715). Base pairs 413 to 1,214 of the TEF sequence from the pyrethrum isolates matched base pairs 1 to 802 (799 of 802 identities) of B. exigua var. exigua (GenBank Accession No. GU349080). All isolates were confirmed as B. exigua var. exigua using morphology and sequencing. Pathogenicity tests were conducted three times in separate glasshouse trials for two of the four isolates. For each isolate, conidial suspensions in water (3 ml/plant) from MEA, adjusted to 5 × 105/ml were applied with Tween 20 (1 drop per 100 ml of water) to 8-week-old pyrethrum plants (five pots per isolate with four plants per pot) using a hand-held spray bottle. Twenty plants were sprayed with water and Tween 20 as nontreated controls. Plants were covered with plastic bags for 48 h after inoculation and examined for symptoms after 15 days at 20°C. Disease incidence (number of symptomatic leaves affected per total number of leaves) of the inoculated plants varied from 7.5 to 9.4%. Noninoculated plants did not develop symptoms. Isolations resulted in cultures morphologically identical on MEA and OA to those inoculated. To our knowledge, this is the first report of B. exigua var. exigua causing disease in pyrethrum. Cultures were deposited in the New South Wales Department of Agriculture collection (DAR79101 to 79104) and TEF and ITS sequences for DAR79101 in GenBank (Accession Nos. JF925328 and JF925329, respectively). Boeremia blight is likely to contribute to the fungal disease complex causing reductions in green leaf area in Australian pyrethrum production. References: (1) M. M. Aveskamp et al. Stud. Mycol. 65:1, 2010. (2) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.

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First Report of Strawberry Dieback Caused by Lasiodiplodia theobromae

Plant Disease ◽

10.1094/pdis-11-13-1192-pdn ◽

2014 ◽

Vol 98 (11) ◽

pp. 1579-1579 ◽

Cited By ~ 6

Author(s):

A. Yildiz ◽

K. Benlioglu ◽

H. S. Benlioglu

Keyword(s):

Management Practice ◽

Fungal Growth ◽

Aerial Mycelium ◽

Plant Diseases ◽

Botryodiplodia Theobromae ◽

Single Spore ◽

Lasiodiplodia Theobromae ◽

First Report ◽

Wide Range ◽

Crown Tissue

With a typical Mediterranean climate, Aydin is the third largest strawberry-producing province, responsible for 13% of the overall strawberry production in Turkey. Strawberries (Fragaria × ananassa Duchesne) are mainly grown in raised, plastic-mulched beds under tunnels and soil solarization is the most effectively used management practice to control soil-borne pathogens. During October 2011 and 2012, 2 months after planting, wilting and collapse of plants were observed on commercial strawberry (cv. strawberry Festival) fields in Sultanhisar town of Aydin Province. Eleven percent of the plants were wilted and died. Symptomatic plants exhibited blackened necrotic discoloration of roots and in the cross section of crowns. A fungus was consistently isolated from pieces of infected tissue cut aseptically from the crowns and placed on potato dextrose agar. Fungus produced white colonies and later turned olivaecious black with dense aerial mycelium after 4 to 5 days incubation at 27°C. Dark brown to black pycnidia that formed on 20- to 30-day-old pure cultures under daylight conditions produced abundant conidia that were two-celled, thick-walled, and oval shaped with longitudinal striations. Single spore isolates from 12 samples were obtained and stored for further identification. The average size of 300 conidia was 25.42 ± 2.12 × 12.87 ± 1.08 μm. The morphology of the fungus was similar to Lasiodiplodia theobromae (Pat.) Griff. & Maubl. (syn. Botryodiplodia theobromae Pat.). To confirm the identity of the isolates, the internal transcribed spacer (ITS) region of ribosomal DNA and the elongation factor 1-alpha gene were amplified with the universal ITS1/ITS4 and EF1-688F/EF1-1251R (1) primers, respectively. The amplicons from 12 isolates were commercially sequenced at Macrogen (Korea) and were deposited in GenBank under consecutive accession numbers KF910369 to KF910380 and KJ641536 to KJ641547. Sequence comparison and phylogenetic analysis revealed that all 12 isolates were closely related and belonged to L. theobromae. Pathogenicity tests were performed by the toothpick technique (2) under greenhouse conditions (28°C, 14/10-h day/night, 70% RH) on potted strawberry plants (cv. strawberry Festival). Toothpicks carrying fungal growth taken from 1-week-old corn meal agar cultures of the tested isolates was placed into the basal crown tissue of the plants by piercing about 5 mm depth. Six plants were inoculated for each isolate and six were treated with sterile toothpick for control. All inoculated plants developed wilting and dieback symptoms resembling those of naturally infected plants within 2 to 3 weeks of incubation. All plants inoculated with the tested isolates collapsed after 4 weeks and showed discoloration of internal crown tissue. Control plants did not exhibit any disease symptoms, and crown tissue was symptomless. L. theobromae was successfully re-isolated from lesions of all inoculated plants. L. theobromae has been reported to cause cankers and dieback in a wide range of hosts in tropical and subtropical regions of the world (3). To the best of our knowledge, this is the first report of L. theobromae causing dieback on strawberry plants. References: (1) A. Alves et al. Fungal Divers. 28:1, 2008. (2) M. E. A. El-Morsi and I. A. Ibrahim. Wudpecker J. Agric. Res. 1:215, 2012. (3) E. Punithalingam. Plant diseases attributed to Botryodiplodia theobromae Pat. J. Cramer, Vaduz, 1980.

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First Report of Diaporthe fusicola Causing Leaf Blotch of Osmanthus fragrans in China

Plant Disease ◽

10.1094/pdis-07-20-1450-pdn ◽

2020 ◽

Author(s):

Yuan-zhi Si ◽

Xiao-Ping Guo ◽

De-Wei Li ◽

Si Wu ◽

Li-Hua Zhu

Keyword(s):

Disease Incidence ◽

Elongation Factor ◽

Morphological Characters ◽

Culture Collection ◽

Bayesian Posterior Probability ◽

Single Spore ◽

Internal Transcribed Spacer Region ◽

Osmanthus Fragrans ◽

Leaf Blotch ◽

First Report

Osmanthus fragrans Lour. is widely distributed in China, Japan, Thailand and India (Zang et al., 2003) and one of the top 10 most well-known flowering plants in China. Since February, 2017, a foliar disease, with a disease incidence of ~60%, occurred on O. fragrans in a community park in Luzhai, Guangxi, China. Symptoms began as round or irregular small yellow spots and became pale brown to gray-brown with time. Small leaf tissues (3 to 4 mm2) cut from lesion margins were surface-sterilized in 75% ethanol for 30 s and 1% NaClO for 90 s before they were rinsed in ddH2O and dried on sterilized filter paper. After drying, the sterilized tissues were plated on potato dextrose agar (PDA) and incubated at 25°C in the dark for 5 days. Five single-spore isolates were obtained and a representative isolate (GH3) was selected and deposited in the China’s Forestry Culture Collection Center. The colony on PDA was white with concentric zonation and white aerial mycelia, but the reverse was yellow. Black pycnidia developed on alfalfa extract + Czapek at 25°C with a 14/10 h light/dark cycle after 17 days. Conidiophores were hyaline, branched, septate, straight to sinuous, 12.4-24 × 1.9-2.5 μm (n = 20). The conidia were fusoid, hyaline, smooth, mostly 2-guttules and measured 7.2 ± 0.7 × 2.3 ± 0.2 μm (n = 50). The morphological characters of pycnidia, conidiophores and conidia of all five isolates matched those of Diaporthe spp. (Gomes et al. 2013). DNA of isolates GH3, GH7 and GH8 was extracted and the internal transcribed spacer region (ITS), partial sequences of elongation factor 1-alpha (EF1-α), calmodulin (CAL), beta-tubulin (β-tub) and histone H3 (HIS) genes were amplified with primers ITS1/ITS4 (White et al. 1990), EF1-728F/EF1-986R and CAL228F/CAL737R (Carbone et al. 1999), βt2a/βt2b and CYLH3F/H3-1b (Glass and Donaldson 1995, Crous et al. 2004), respectively. The sequences of GH3, GH7 and GH8 were deposited in GenBank (GH3: Accession nos. MT499213 for ITS, MT506473 to MT506476 for EF1-α, β-tub, HIS, and CAL; GH7: MT856374 and MT860397 to MT860400; GH8: MT856375 and MT860401 to MT860404). BLAST results showed that the ITS, EF1-α, β-tub, HIS, and CAL sequences of GH3 were highly similar with sequences of Phomopsis sp. [LC168784 (ITS), Identities = 506/506(100%)], Diaporthe fusicola [MK654863 (EF1-α), Identities = 274/275(99%)], D. amygdali [MK570513 (β-tub), Identities = 461/461(100%)], D. fusicola [MK726253 (HIS), Identities = 403/403(100%)] and D. amygdali [KC343263 (CAL), Identities = 428/428(100%)], respectively. A maximum likelihood and Bayesian posterior probability analyses using IQtree v. 1.6.8 and Mr. Bayes v. 3.2.6 with the concatenated sequences placed isolates GH3, GH7 and GH8 in the D. fusicola cluster and separated them from D. eres and D. osmanthi, which were previously reported from Osmanthus spp. (Gomes et al., 2013; Long et al., 2019). Based on the multi-gene phylogeny and morphology, all three isolates were identified as D. fusicola. The pathogenicity of GH3 was tested on 1-yr-old seedlings of O. fragrans. Healthy leaves were wounded with a sterile needle and then inoculated with either 5-mm mycelial plugs cut from the edge of a 5-day-old culture of GH3 or 10 μL of conidial suspensions (106 conidia/mL). Control leaves were treated with PDA plugs or ddH2O. Three plants were used for each treatment. The plants were covered with a plastic bag after inoculation and sterilized H2O was sprayed into the bags twice/day to maintain humidity and kept in a greenhouse at the day/night temperatures at 25 ± 2°C/16 ± 2°C. Lesions appeared 3 days later. No lesions were observed on control leaves. The same fungus was re-isolated from lesions. This is the first report of D. fusicola causing leaf blotch on O. fragrans. These results form the basis for developing effective strategies for monitoring and managing this potential high-risk disease.

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STUDIES ON THE FUSARIUM OF MUSKMELON WILT: I. PATHOGENIC AND CULTURAL STUDIES WITH PARTICULAR REFERENCE TO THE CAUSE AND NATURE OF VARIATION IN THE CAUSAL ORGANISM

Canadian Journal of Research ◽

10.1139/cjr45c-002 ◽

1945 ◽

Vol 23c (1) ◽

pp. 16-43 ◽

Cited By ~ 14

Author(s):

John J. Miller

Keyword(s):

Disease Incidence ◽

Ultra Violet ◽

Aerial Mycelium ◽

Wild Type ◽

Cultural Interaction ◽

Causal Organism ◽

Highly Pathogenic ◽

General Application ◽

Serious Disease ◽

The Stability

During the past decade a serious disease of muskmelon has appeared in Ontario. From diseased plants a Fusarium has been isolated, which proved to be highly pathogenic to muskmelons in infection experiments. Results indicate that the wilt organism occurs in nature as a form (or forms) that, when cultured on most artificial media, produces abundant aerial mycelium and this has been termed the 'wild type.' Mutation toward loss of aerial mycelium and darkening of the submerged mycelium is frequently observed in culture and, since many of the mutants are more aggressive than the parent, they tend to displace it. Evidence is presented that the wild type is genetically very stable in its natural environment. Since, moreover, certain of the commoner mutants caused less disease incidence under field conditions than the wild type, it is considered that variation of the sort observed in culture, if it does occur in the field, is unlikely to be of importance in the field pathology of the disease. The stability of the wild type in sterilized soil and soil agar indicates that these substrates may be of value for maintaining Fusaria in the pure state. Mutations were induced by irradiating spores with ultra-violet light. In general, these resembled those that appeared spontaneously and both groups were less pathogenic than the wild type. A phenomenon termed 'cultural interaction' was observed between certain of the mutant cultures and the wild type. Since this appeared to be of a specific nature, it may be of some taxonomic value in diagnosing species of Fusarium. The suggestion is offered that the concept of the 'wild type' may be of general application throughout the genus Fusarium.

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Detecção rápida de Ceratocystis fimbriata em lenho infetado de eucalipto, mangueira e outros hospedeiros lenhosos

Fitopatologia Brasileira ◽

10.1590/s0100-41582005000500016 ◽

2005 ◽

Vol 30 (5) ◽

pp. 543-545 ◽

Cited By ~ 2

Author(s):

Francisco A Ferreira ◽

Luis A Maffia ◽

Evander A Ferreira

Keyword(s):

Theobroma Cacao ◽

Mangifera Indica ◽

Ceratocystis Fimbriata ◽

Lasiodiplodia Theobromae

Desenvolveu-se uma técnica de detecção rápida de Ceratocystis fimbriata em lenho de eucalipto (Eucalyptus spp.) infetado, visualizando-se clamidósporos (aleuroconídios) ao microscópio ótico comum, em vasos do xilema, medula e raios medulares, a partir de cortes histopatológicos à mão livre, feitos com lâmina de barbear, ao microscópio estereoscópico. O tempo médio gasto para a detecção do patógeno, do corte histopatológico tangencial à total visualização dos clamidósporos ao microscópio ótico comum, foi de 3,5 min e bem menos utilizando-se corte longitudinal passando pela medula, contra, no mínimo, quatro a cinco dias, usando-se outras técnicas como o isolamento em BDA, deposição de fragmentos de lenho doente entre fatias de cenoura usadas como isca, ou pedaços de lenhos doentes deixados em câmara úmida. Essa técnica histopatológica é também viável para a detecção do patógeno em outros hospedeiros lenhosos e, inclusive, para a detecção de hifas de Lasiodiplodia theobromae, mesmo quando esses dois fungos estavam num mesmo tecido, como na doença-complexo seca de mangueira investigada no Sultanato de Omã. Além de eucalipto, mangueira (Mangifera indica) e cacaueiro (Theobroma cacao) é provável que essa técnica possa ser estendida para outros hospedeiros lenhosos de C. fimbriata.

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Epidemiology of Mango Malformation in Guerrero, México, with Traditional and Integrated Management

Plant Disease ◽

10.1094/pdis.1999.83.3.223 ◽

1999 ◽

Vol 83 (3) ◽

pp. 223-228 ◽

Cited By ~ 27

Author(s):

D. H. Noriega-Cantú ◽

D. Téliz ◽

G. Mora-Aguilera ◽

J. Rodríguez-Alcazar ◽

E. Zavaleta-Mejía ◽

...

Keyword(s):

Wind Speed ◽

Integrated Management ◽

Disease Incidence ◽

Mangifera Indica ◽

Spore Density ◽

Cost Rate ◽

Average Maximum ◽

Fusarium Sp ◽

Epidemic Development ◽

Benefit Cost

The temporal progress of malformation (MM) of mango (Mangifera indica) was studied from 1993 to 1995 with three management technologies applied to commercial plantations in North Guerrero, Mexico. Management influenced shoot production and thus determined the dynamics of epidemics. Environmental factors also affected disease incidence, particularly through an apparent effect on inoculum dispersal. In general, integrated management (IM), consisting of pruning, acaricide, and fungicide sprays, resulted in slower rates of epidemic development, lower levels of initial and final disease, and lesser areas under the disease progress curves. In the first cycle, IM increased yield per tree by 51% in relation to high technology (HT) and 74% in relation to lower traditional technology (LT), representing a benefit-cost rate of 2.8 and 3.3, respectively. Change of malformation incidence was correlated positively with the number of macroconidia of Fusarium sp. trapped in the canopy (r = 0.90, P = 0.0001) and wind speed (r = 0.83, P = 0.0001); both variables lagged over a 4-month period. The greatest change in malformation occurred during the main vegetative flush, which occurred 3 to 6 months after picking the fruit (May). The accumulated proportion of diseased shoots was correlated with the following variables measured over a 1-week period: average maximum daily temperature (r = -0.68, P = 0. 01), average temperature per hour (r = -0.59, P = 0.04), average number of hours with relative humidity ≥60% (r = -0.82, P = 0.001), and wind speed (r = 0.94, P = 0.0001). In general, the greatest spore density was found during the rainy season, with a morning periodicity showing the highest correlation with wind speed (r = 0.812, P = 0.0001). F. subglutinans was isolated consistently from diseased (86%) and asymptomatic (5%) vegetative and flowering shoots.

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First report of Colletotrichum siamense Causing Blossom Blight on Thai basil (Ocimum basilicum L.) in Malaysia

Plant Disease ◽

10.1094/pdis-06-20-1371-pdn ◽

2020 ◽

Author(s):

Siti Izera Ismail ◽

Nur Adlina Rahim ◽

Dzarifah Zulperi

Keyword(s):

Disease Incidence ◽

Its Region ◽

Ocimum Basilicum ◽

Distilled Water ◽

Single Spore ◽

First Report ◽

Plastic Bags ◽

Colletotrichum Siamense ◽

Primer Sets ◽

Acca Sellowiana

Thai basil (Ocimum basilicum L.) is widely cultivated in Malaysia and commonly used for culinary purposes. In March 2019, necrotic lesions were observed on the inflorescences of Thai basil plants with a disease incidence of 60% in Organic Edible Garden Unit, Faculty of Agriculture in the Serdang district (2°59'05.5"N 101°43'59.5"E) of Selangor province, Malaysia. Symptoms appeared as sudden, extensive brown spotting on the inflorescences of Thai basil that coalesced and rapidly expanded to cover the entire inflorescences. Diseased tissues (4×4 mm) were cut from the infected lesions, surface disinfected with 0.5% NaOCl for 1 min, rinsed three times with sterile distilled water, placed onto potato dextrose agar (PDA) plates and incubated at 25°C under 12-h photoperiod for 5 days. A total of 8 single-spore isolates were obtained from all sampled inflorescence tissues. The fungal colonies appeared white, turned grayish black with age and pale yellow on the reverse side. Conidia were one-celled, hyaline, subcylindrical with rounded end and 3 to 4 μm (width) and 13 to 15 μm (length) in size. For fungal identification to species level, genomic DNA of representative isolate (isolate C) was extracted using DNeasy Plant Mini Kit (Qiagen, USA). Internal transcribed spacer (ITS) region, calmodulin (CAL), actin (ACT), and chitin synthase-1 (CHS-1) were amplified using ITS5/ITS4 (White et al. 1990), CL1C/CL2C (Weir et al. 2012), ACT-512F/783R, and CHS-79F/CHS-345R primer sets (Carbone and Kohn 1999), respectively. A BLAST nucleotide search of ITS, CHS-1, CAL and ACT sequences showed 100% similarity to Colletotrichum siamense ex-type cultures strain C1315.2 (GenBank accession nos. ITS: JX010171 and CHS-1: JX009865) and isolate BPDI2 (CAL: FJ917505, ACT: FJ907423). The ITS, CHS-1, CAL and ACT sequences were deposited in GenBank as accession numbers MT571330, MW192791, MW192792 and MW140016. Pathogenicity was confirmed by spraying a spore suspension (1×106 spores/ml) of 7-day-old culture of isolate C onto 10 healthy inflorescences on five healthy Thai basil plants. Ten infloresences from an additional five control plants were only sprayed with sterile distilled water and the inoculated plants were covered with plastic bags for 2 days and maintained in a greenhouse at 28 ± 1°C, 98% relative humidity with a photoperiod of 12-h. Blossom blight symptoms resembling those observed in the field developed after 7 days on all inoculated inflorescences, while inflorescences on control plants remained asymptomatic. The experiment was repeated twice. C. siamense was successfully re-isolated from the infected inflorescences fulfilling Koch’s postulates. C. siamense has been reported causing blossom blight of Uraria in India (Srivastava et al. 2017), anthracnose on dragon fruit in India and fruits of Acca sellowiana in Brazil (Abirami et al. 2019; Fantinel et al. 2017). This pathogen can cause a serious threat to cultivation of Thai basil and there is currently no effective disease management strategy to control this disease. To our knowledge, this is the first report of blossom blight caused by C. siamense on Thai basil in Malaysia.

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