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Malabar spinach (Basella alba L.) is a fast-growing, perennial vegetable crop grown largely in the tropics of Asia and Africa. This crop is widely used in the cuisine of different regions for its thick, semisucculent leaves, mild flavor, and mucilaginous texture. Leaf spots were observed on both surfaces of symptomatic leaf samples received from a home garden in Homestead, FL in November 2009. The necrotic lesions (up to 2 mm in diameter) were round, semicircular, or irregular-shaped with grayish centers surrounded by dark brown borders. A fungus was consistently isolated from symptomatic tissues on clarified V8 (CV8) agar. Fungal colonies on CV8 agar were black and velvet-like with minimal mycelial growth and conidiophores were dark brown, simple, borne singly or in groups upon the substrate. Conidia were straight, pale to medium golden brown, rounded at the ends with three to six septa, and on average measured 75 × 15 μm (48 to 97 × 9 to 18 μm). Cultural and conidial characteristics of the isolates were closely similar to those of a Bipolaris sp. (1). The internal transcribed spacer (ITS) region (~570 bp) of rDNA was amplified using the primers ITS1/ITS4 and sequenced bidirectionally (GenBank Accession No. JF506092). Subsequent database searches by the BLASTN program indicated that the resulting sequence had a 95% identity over 531 bp with the corresponding gene sequence of Bipolaris portulacae (GenBank Accession No. AY004778.1), a fungal pathogen reported to cause leaf spot on purslane (Portulaca oleracea) (2,3). However, our isolate has consistently smaller conidia and does not match descriptions of B. portulacae (BPI 871173, U.S. National Fungus Collections). The pathogenicity was confirmed through inoculation of healthy Malabar spinach plants with conidia of the isolate reproduced on CV8. Six Malabar spinach plants were inoculated with a suspension containing 1 × 106 conidia per ml and sprayed until runoff (approximately 15 ml per plant) with a handheld pressurized canister. Another six noninoculated plants served as a control. Immediately after inoculation, plants were covered with plastic bags for 24 h to maintain high relative humidity and maintained in a greenhouse under ambient conditions. Ten days after inoculation, the symptoms described above were observed on leaves of all inoculated plants, whereas symptoms did not develop on the control plants. A Bipolaris sp. was reisolated and identified by the above methods, fulfilling Koch's postulates. This pathogenicity test was carried out three times. To our knowledge, this is the first report of a Bipolaris sp. affecting Malabar spinach in Florida. Further work should be conducted to confirm identity of these isolates. Because of limited plantings of Malabar spinach, the economic importance of this disease in Florida is currently not known. Nevertheless, this pathogen poses a threat to the growing market of continuously produced oriental vegetables in Florida. References: (1) J. L. Alcorn. Mycotaxon 39:361, 1990. (2) S. A. Alfieri, Jr. et al. Bull. 14. Index of Plant Diseases in Florida (Revised). Florida Dep. Agric. Consumer Serv., Div. Plant Ind., 1984. (3) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology and Microbiology Laboratory. ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , 25 January 2010.

Indian spinach (Basella rubra L.) is a red stem species of Basella that is cultivated worldwide as an ornamental and the aerial parts are also consumed as a vegetable. In May of 2011, symptoms of damping-off were observed on approximately 10% of the plants at the stem base around the soil line of seedlings in a greenhouse in Homestead, FL. Lesions were initially water soaked, grayish to dark brown, irregular in shape, and sunken in appearance on large plants, causing the infected seedlings to collapse and eventually die. Symptomatic stem tissue was surface sterilized with 0.6% sodium hypochlorite, rinsed in sterile distilled water, air dried, and plated on potato dextrose agar (PDA). Plates were incubated at 25°C in darkness for 3 to 5 days. A fungus was isolated in all six isolations from symptomatic tissues on PDA. Fungal colonies on PDA were light gray to brown with abundant growth of mycelia, and the hyphae tended to branch at right angles when examined under a microscope. A septum was always present in the branch of hyphae near the originating point and a slight constriction at the branch was observed. Neither conidia nor conidiophores were found from the cultures on PDA. The characteristics of hyphae, especially the right angle branching of mycelia, indicate close similarity to those of Rhizoctonia solani (2,3). The internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced (GenBank Accession No. JN545836). Subsequent database searches by the BLASTN program indicated that the resulting sequence had a 100% identity over 472 bp with the corresponding gene sequence of R. solani anastomosis group (AG) 4 (GenBank Accession No. JF701752.1), a fungal pathogen reported to cause damping-off on many crops. Pathogenicity was confirmed through inoculation of healthy India spinach plants with the hyphae of isolates. Four 4-week-old plants were inoculated with the isolates by placing a 5-mm PDA plug of mycelia at the stem base and covering with a thin layer of the soil. Another four plants treated with sterile PDA served as a control. After inoculation, the plants were covered with plastic bags for 24 h and maintained in a greenhouse with ambient conditions. Four days after inoculation, water-soaked, brown lesions, identical to the symptoms described above, were observed on the stem base of all inoculated plants, whereas no symptoms developed on the control plants. The fungus was isolated from affected stem samples, and the identity was confirmed by microscopic appearance of the hyphae and sequencing the ITS1/ITS4 intergenic spacer region, fulfilling Koch's postulates. This pathogenicity test was conducted twice. R. solani has been reported to cause damping-off of B. rubra in Ghana (1) and Malaysia (4). To our knowledge, this is the first report of damping-off caused by R. solani AG-4 on Indian spinach in Florida and the United States. With the increased interest in producing Asian vegetables for food and ornamental purposes, the occurrence of damping-off on Indian spinach needs to be taken into account when designing programs for disease management in Florida. References: (1) H. A. Dade. XXIX. Bull. Misc. Inform. 6:205, 1940. (2) J. R. Parmeter et al. Phytopathology 57:218, 1967. (3) B. Sneh et al. Identification of Rhizoctonia species. The American Phytopathological Society, St Paul, MN, 1991. (4) T. H. Williams and P. S. W. Liu. Phytopathol. Pap. 19:1, 1976.

Sweet basil (Ocimum basilicum L.) is the most important annual culinary herb in the United States. It is grown commercially for the fresh market as a food flavor and as a source of essential oils and oleoresin for manufacturing perfumes and aromatherapy products. In November 2010, grayish to dark, necrotic lesions were observed on the stem of sweet basil plants of the cv. Genovese grown in 10-cm diameter pots containing “Fafard” soilless medium in a greenhouse in Homestead, FL. Symptoms started 3 weeks after planting at the soil line and extended 2 to 5 cm up the stem. Nearly 99% of the plants were symptomatic after another 1 to 2 weeks. The lesions coalesced and reached as high as 12 to 15 cm up the stem. Severely affected plants were stunted (as short as 10 cm compared to 25 cm for non-infected plants), became weak, and lodged as infection progressed. Stem sections from five diseased plants were surface sterilized with 0.6% sodium hypochlorite for 15 min, plated on potato dextrose agar (PDA), and incubated in the dark at 25°C. Pale to pink, slimy, appressed colonies with whitish, sparse aerial mycelia grew on PDA. Hyaline, smooth, ellipsoidal conidia, each tapering gradually to a broadly rounded apex and base, with one to two guttulation droplets, were observed microscopically. Conidial dimensions averaged 9.4 (4.2 to 13.2) × 2.5 (2.2 to 3.2) μm. The isolated fungus was morphologically similar to Plectosporium tabacinum (van Beyma) M.E. Palm, W. Gams et Nirenberg (synonyms M. tabacinum (van Beyma) von Arx, 1984 and F. tabacinum (Gams & Gerlagh, 1968)) (3). Fungal DNA was extracted and an 834-bp fragment of partial 28S rDNA was amplified with primers LROR and LR5 (4), and the amplified fragment was sequenced (GenBank Accession No. JQ999955). Sequence comparison using BLAST revealed 99% identity with that of Plectosphaerella cucumerina (GenBank Accession No. U17399). Pathogenicity tests were carried out three times by inoculating three 2-week-old, healthy basil seedlings in each test with a conidial suspension of the isolate sprayed onto the plants at 1 × 106 conidia/ml. Non-treated control plants were sprayed similarly with deionized water. Lesions identical to the above descriptions appeared on stems of all inoculated plants 2 to 4 days after inoculation (plants were held at 25°C), and the same pathogen was reisolated on PDA. Additionally, leaves of inoculated plants showed extensive chlorosis and necrosis. All noninoculated plants remained symptomless. Black leg, caused by P. tabacinum, was reported on hydroponically grown basil in Indiana (1). It was also reported to cause necrosis on the stem of basil plants in Italy (2). In Homestead, FL, seven cultivars (Cinnamon, Genovese, Broad leaf Italian, Red Rubin, Lemon, Thai, and Common basil) of basil grown in plastic pots have shown black leg symptoms in the greenhouse. To our knowledge, this is the first report of P. cucumerina (anamorph P. tabacinum) causing black leg on greenhouse grown basil in Florida. Approximately 50% of the 12-week-old plants in a field trial at Homestead, FL, showed identical symptoms in spring 2012. The high incidence of this disease in Homestead and the potentially aggressive nature of the pathogen on foliage suggest a need for development of effective management strategies. References: (1) D. Egel et al. Plant Dis. 94:484. 2010. (2) A. Garibaldi et al. Plant Dis. 81:124. 1997. (3) M. Palm et al. Mycologia. 87:397. 1995. (4) Rehner and Samuels. Can. J. Bot. 73:816. 1995.