First Outbreak of Bacterial Leaf Spot Caused by Xanthomonas campestris on Canola in Argentina

Plant Disease
S A Gaetán, N López

Abstract

Canola (Brassica napus) is an alternative crop to wheat in Argentina and ~16,000 ha are grown commercially in southern Buenos Aires Province. During 2003, experimental field plots of canola plants located at Agronomy Faculty, University of Buenos Aires, in Buenos Aires were severely damaged by a bacterial leaf spot. Average disease incidence across 25 2- to 5-month-old canola cultivars was 58% (range = 27 to 89%). During 2004, identical infection associated with blackened veins (8 to 12% of plants) were found in two commercial fields and experimental crops (rosette and flowering stages) in Tres Arroyos in southern Buenos Aires Province. Symptoms observed on adaxial surfaces consisted of v-shaped necrotic lesions on leaf margin surrounded by yellow halos. Yellow bacterial ooze was found on young lesions. The advanced phases of the disease included lesion enlargement, foliar chlorosis, and death of leaves. The disease developed from the lower leaves to the apex, resulting in complete leaf necrosis and defoliation. Ten samples (five plants per sample) with lesions were arbitrarily collected from 2003 to 2004 from commercial and experimental canola crops. Diseased leaf tissue was surface sterilized in 0.50% sodium hypochlorite for ...Continue Reading

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