Taro (Colocasia esculenta (L.) Schott) is an important food crop cultivated for its edible tubers in Ghana. In May 2009, outbreaks of a destructive leaf disease were observed on several taro farms in the Atiwa, East-Akim, Fanteakwa, West-Akim, and New Juaben districts of the Eastern Region of Ghana. Symptoms began on leaves as small, brown, water-soaked lesions that enlarged and coalesced into large lesions with yellow exudate, ultimately leading to the defoliation and death of plants. Symptoms were suggestive of taro leaf blight (TLB) caused by Phytophthora colocasiae Raciborski (3). By August 2010, the disease had spread to other taro-growing regions in Ghana. To identify the pathogen, leaf tissue from lesion margins were excised and plated on carrot agar and V8 selective media for Phytophthora and incubated at 27°C for 5 days (2). Growth from diseased tissue was used for morphological characterization. Sporangia were ovoid, hyaline, papillate, caducous, 30 to 60 × 17 to 28 μm, and pedicels were 3.5 to 10 μm long. Genomic DNA was isolated from pure cultures of two isolates, PCg11-2 from Oseim (6°15′N, 0°27′E) and PCg11-5 from Oyoko (6°8′N, 0°17′W). Ribosomal DNA ITS1, 5.8S and ITS2 were amplified by PCR using the ITS1 and ITS4 primers (4). The resultant 784-bp amplicons were sequenced (GenBank Accession Nos. JN662439 and JN662440). Sequences of both isolates were identical. A BLASTn search of these sequences revealed maximum homology of 99% with the sequence of P. colocasiae strains from blighted taro leaves in Nigeria (GenBank Accession No. HQ602756), Hawaii (GenBank Accession No. GU258997), and several strains in Asia and the South Pacific. On the basis of morphological characteristics and nucleotide homology, the isolates were identified as P. colocasiae. To fulfill Koch's postulates, 30 leaf discs from 3-month-old plants were inoculated with 10 μl of a suspension of 3 × 105 zoospores per ml (2). Leaf discs were incubated in the dark at 27°C on wet foam in plastic trays for 5 days. All inoculated discs developed blight symptoms similar in appearance to those observed on diseased taro in the fields. Control discs remained asymptomatic. P. colocasiae was reisolated from leaf discs and its identity confirmed by morphological characteristics. To our knowledge, this is the first report of TLB and P. colocasiae in Ghana. Occurrence of TLB was recently reported in Nigeria (1). The recent occurrence of TLB in both Nigeria and Ghana threaten the taro-growing regions of West and Central Africa. Disease surveys and a management strategy that includes resistant varieties are urgently needed. References: (1) R. Bandyopadhyay et al. Plant Dis. 95:618, 2011. (2) A. Drenth and B. Sendall. Practical Guide to Detection and Identification of Phytophthora. Version 1.0. CRC for Tropical Plant Protection. Brisbane, Australia, 2001. (3) M. Raciborski. Java Batavia Bull. 19:189, 1900. (4) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, San Diego, CA, 1990.

Severity of storage rots in different sections of white yam tubers (Dioscorea rotundata Poir.) was investigated. Yam samples with rots were collected from a yam barn and from selected markets in Accra, Ghana, to identify the most predominant pathogens associated with the rots. Nine fungal spoilage microorganisms, including Aspergillus flavus, Aspergillus niger, Botryodiplodia theobromae, Fusarium culmorum, Fusarium oxysporium, Fusarium sp., Penicillium brevi-compactum, Penicillium sp. and Rhizopus stolonifer and a bacterium species Erwinia carotovora were identified. The mean incidence of occurrence of the organisms on rotten tissues ranged from 1.2% to 28.5%. Of the 10 microorganisms isolated, B. theobromae, F. oxysporium and R. stolonifer were the most frequently encountered spoilage microorganisms in the markets. E. carotovora, Fusarium solani and Penicillium sp. were relatively sparse (incidence not exceeding 3%) compared to the other yam spoilage microorganisms. The surface area and weight of necrotic tissue induced by the spoilage fungi in the various zones of the tubers over a 28-day storage period were assessed. All the spoilage microorganisms produced rots in the yams, although to different degrees. The severity of the rots increased in weight and area over the period when the tubers were in store but were normally not significantly different in the zones of tubers. There was, however, a linear progression of rots in the various zones of the yam tubers. Although there was generally no significant (P ! 0.05) difference in the severity of rots induced by the different microorganisms in the tubers, R. stolonifer commonly induced more rot in the zones of the tubers compared to B. theobromae and F. oxysporium.

Theobroma cacao (chocolate tree) is currently under serious threat from thread blight disease (TBD), which has been attributed to the causal agent Marasmiellus scandens in other regions of the world. TBD in Ghana has similar symptomology but variable signs. This study sought to determine whether TBD in Ghana was caused by a single agent and whether Marasmiellus scandens was a significant agent of TBD. Forty-eight isolates were collected from eight geographical locations in Ghana for morphological and molecular characterization. Disease signs occurred as vegetative rhizomorphs or hyphal aggregates, which were classified into five morphotypes: A, abundant thin, black, “horse hair”-type rhizomorphs; B, scattered brown rhizomorphs; C, whitish to brownish-white; D, faint cream or dull white; and E, aggregates of shiny or silky white hyphae. Sequencing and analyses of three loci—the internal transcribed spacer region of the nuclear ribosomal repeat, nuclear large subunit, and mitochondrial small subunit—detected four species, all members of the Marasmiaceae, causing TBD-like disease. These were identified as Marasmius crinis-equi (morphotype A), Marasmius tenuissimus (morphotypes B and C), Marasmiellus palmivorus (morphotype E), and Marasmiellus scandens (morphotype D). Marasmius tenuissimus, the most frequently isolated TBD fungus in this study, is primarily an Asian fungus and not previously associated with diseases of cacao. Marasmiellus palmivorus, the second most frequently isolated fungus, is a pan-tropical pathogen with a broad host range; this is the first report of the fungus causing TBD on cacao. Marasmius crinis-equi also has a broad pan-tropical distribution and host range and causes thread blight on several tropical tree crops. Surprisingly, Marasmiellus scandens, the most frequently cited agent of TBD in cacao, made up only 8% of the isolates.

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Citrus is one of the most important crops in Ghana, representing a large proportion of the fresh fruit consumed in the country. In 2004, symptoms consisting of necrotic leaf spots of about 1 cm in diameter with light brown centers and dark brown margins surrounded by a yellow halo were first observed in sweet orange (Citrus sinensis) and mandarin (C. reticulata) orchards in the Eastern Region of Ghana. Fruits with raised corky lesions of up to 3 to 4 cm in diameter with yellow halos were also observed. Affected fruit had longitudinal and transversal cracks in the rind with the internal locules exposed. Juice content in diseased fruit was strongly reduced, making them unsuitable for fresh consumption or processing. The disease expanded to the Central and Ashanti Regions, with incidences over 95% and estimated yield losses of about 50 to 90%. Symptomatic leaves and fruit collected in Kade in the Eastern Region were surface disinfested with 0.5% NaOCl for 5 min and small fragments from lesions were plated onto malt extract agar (MEA). Slow-growing fungal colonies were isolated from about 5% of the affected tissues plated after 5 days of incubation at 24 to 26°C, and were transferred to V-8 juice agar and MEA. Plates were incubated for 30 days at 24 to 26°C with 12 h of fluorescent light and 12 h of dark for morphological examination. Colonies were gray in the upper side and dark green on the underside. Conidia produced in culture were mostly solitary or in short chains of 2 to 6 spores, hyaline to pale brown, cylindrical, with rounded apex and base truncated. Conidia were 24 to 82 × 4 to 6 μm, with up to 3 to 5 transverse septa and no longisepta. The 5.8S, ITS2, and 28S ribosomal RNA (rRNA) regions were amplified using the primers ITS1 and ITS4 (3) and sequenced from DNA extracted from the isolate MC-39, obtained from sweet orange leaves in Kade (GenBank Accession No. KF111755). The sequence had 99% identity (total score 819, 85% coverage) with that of Pseudocercospora angolensis (T. Carvalho & O. Mendes) Crous & U. Braun epitype strain CBS 112933 (GU269836) (1). Pathogenicity tests were performed twice on 12-week-old detached fruit of sweet orange cv. Valencia Late of about 4 to 5 cm in diameter. Inoculations were performed using a conidial suspension (3.0 × 105 conidia/ml water) by spraying fruit to run off, brushing the rind, dipping for 6 min, or injecting 2 ml in the albedo. Twenty-two isolates were evaluated and 18 fruit were used for each inoculation technique, isolate and experiment. Fruit treated with sterile distilled water were used as controls. Inoculated fruit were maintained in humid chambers at 24 to 26°C. Disease incidence on inoculated fruit varied from 40.7% to 92.6% and severity from 2 to 3 to 3 to 11 lesions per fruit, depending on the isolate and inoculation technique. No symptoms were observed on control fruit. Fungal colonies morphologically identified as P. angolensis were reisolated from lesions on inoculated fruit, but not from asymptomatic control fruit. Based on these results, the disease was identified as Pseudocercospora fruit and leaf spot of citrus caused by P. angolensis. Until this present report, Ghana was considered one of the few countries in Central Africa that was still free of this citrus disease (2). References: (1) P. W. Crous et al. Stud. Mycol. 75:37, 2013. (2) A. A. Seif and R. J. Hillocks. Int. J. Pest Manag. 39:44, 1993. (3) T. J. White et al. Pages 315-322 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.