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Abstract
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Citrus bacterial canker, caused by Xanthomonas citri subsp. citri (Xcc), is a widespread disease in citrusproducing
areas of the tropics and subtropics. It is a serious threat to most commercial citrus cultivars and species. In
this study, aggressiveness of different isolates of Xcc was determined on leaves of Citrus aurantiifolia, Citrus limon
‘Eureka’ and Citrus sinensis, and the population dynamics of isolates of two Xcc pathotypes (A and A*) was evaluated
on eight plant species considered weeds of citrus, including Amaranthus caudatus, Medicago sativa, Sorghum
halepense, Xanthium strumarium, Portulaca oleracea, Avena ludoviciana, Plantago lanceolata and Chenopodium
album under greenhouse conditions. Isolates varied from aggressive to weakly aggressive on the basis of the intensity
and persistence of water soaking and the development of necrosis 12 days post-inoculation. Both Xcc pathotypes
multiplied on all plant species tested except Portulaca oleracea up to 20 days post-inoculation under greenhouse
conditions. A high bacterial growth rate was observed on Medicago sativa and Plantago lanceolata. Strains of the A*
pathotype successfully proliferated on all weeds except Portulaca oleracea, attaining a population density even higher
than that of the A pathotype. The results clearly suggest that weed management is an important strategy in controlling
canker disease in citrus-growing areas.
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