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First confirmed report of citrus black spot caused by Guignardia citricarpa on sweet oranges ( Citrus sinensis ) in Uganda
Author(s) -
Reeder R.,
Kelly P. L.,
Harling R.
Publication year - 2009
Publication title -
plant pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.928
H-Index - 85
eISSN - 1365-3059
pISSN - 0032-0862
DOI - 10.1111/j.1365-3059.2008.01966.x
Subject(s) - biology , black spot , pycnidium , conidium , citrus × sinensis , botany , orange (colour) , spots , horticulture , potato dextrose agar , leaf spot , mycelium , agar , genetics , bacteria
Blueberry ( Vaccinium corymbosum ) production in Argentina has grown remarkably in the last 8 years due to the high demand worldwide in the off-season fresh market. Since it is a new crop in Argentina, diseases are just starting to become problematic for farmers. Surveys have been conducted since 2000 to detect new pathogenic associations and to evaluate their distribution, incidence and severity in different blueberry varieties and localities. Blueberry plants cv. Duke with dieback, and bud and branch blight, were observed in the winter of 2006 in La Plata, Buenos Aires province. Diseased pieces were washed with running water, disinfected with 2% sodium hypochlorite, then 70% alcohol, rinsed in sterile distilled water, plated on carrot agar (CA), and incubated for 12 h under near UV light until colony maturation. Conidia were single, fusiform, straight or slightly curved, 30–50 (46·7) × 11–22 (18·4) μ m, 3–7 distoseptate (mostly 5–6), pale to mid-golden brown, with bipolar germination. Based on these characteristics, the fungus was identified as Bipolaris cynodontis (Sivanesan, 1987). The strain was deposited in the culture collection of the Instituto de Micología Spegazzini (La Plata, Buenos Aires, Argentina), No. 1018. Pathogenicity tests were carried out using 2-month-old blueberry plants cv. O’Neal inoculated with a suspension containing 10 6 conidia mL –1 . Sterile distilled water was sprayed on controls. Plants were maintained in a humidity chamber at 20 ° C ± 2 ° C for 48 h, and incubated under 12 h light until symptoms developed. The fungus was recovered from inoculated plants that displayed similar symptoms to those observed in the field. Control plants did not show symptoms. Bipolaris cynodontis has been isolated from Cynodon, other grasses, apple, pine, Ipomoea spp. and Lycopersicon spp. and is seed-borne on Agropyron , Hordeum and Triticum spp. (Sivanesan, 1987). In Argentina, this fungus has been found on leaves of Bromus unioloides (Sisterna & Wolcan, 1989) and Cynodon dactylon (Sisterna & Dal Bello, 1991–1992) and on cereal seeds (Sisterna, 1987). This is the first report of Bipolaris cynodontis on blueberry in Argentina.