Planta Daninha (2013) 31, 1-9

E.V.V. Varejão, A.J. Demuner, L.C.A. Barbosa, R.W. Barreto and B.S. Vieira (2013)
Toxicidade de filtrados de cultura de Alternaria euphorbiicola em folhas de Euphorbia heterophylla
[Phytotoxicity of Alternaria euphorbiicola culture filtrates in Euphorbia heterophylla leaves]
Planta Daninha 31 (1), 1-9
Abstract: The fungal species Alternaria euphorbiicola was identified as causal agent of inflorescence necrosis, leaf blight, and stem canker in Euphorbia heterophylla (wild poinsettia), a major weed responsible for great agricultural losses in Brazil. The application of spore suspensions of the fungus on specimens of the host plant resulted in production of disseminated necrosis at short time intervals (24 to 48 hours) after application. These observations led to the hypothesis that the fungus could produce phytotoxins capable of causing damage to the plant. The objective of this study was to investigate the in vitro production of phytotoxins by A. euphorbiicola under different growth conditions. The results showed that the culture medium and growth conditions influenced the phytotoxicity of the culture filtrates. Growing the fungus under agitation in the dark resulted in higher production of phytotoxic metabolites. The filtrate from the culture formed in modified Jenkins-Prior medium, under agitation, at 28 ^oC in the dark showed the highest phytotoxic activity. This filtrate produced foliar necrosis and defoliation in E. heterophylla and was subjected to extraction followed by bioassay-guided fractionation. A chromatographic fraction consisting mainly of long-chain fatty acids produced bleached lesions and necrosis of the leaves, the same symptoms observed after inoculation of the fungus in the host plant. These results suggest the involvement of these phytotoxic fatty acids in the process of tissue invasion of E. heterophylla by A. euphorbiicola.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
(original language: Portuguese)
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Database assignments for author(s): Robert Weingart Barreto

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Euphorbia heterophylla (weed)
Alternaria euphorbiicola (weed pathogen)	Euphorbia heterophylla (weed)