Fungi pathogenic on wild radish (Raphanus raphanistrum L.) in northern Tunisia

• Published in: Phytopathologia mediterranea 2009-09, Vol.48 (2), p.205-213
• Main Authors: Djebali, N, Scott, J.K, Jourdan, M, Souissi, T
• Format: Article
• Language: English
• Subjects: biological control; biological control agents; broadleaf weeds; carbendazim; field experimentation; flowering; foliar diseases; fungal diseases of plants; life cycle (organisms); mycoherbicides; new host records; phenology; plant pathogenic fungi; Raphanus raphanistrum; seasonal development; seed development; seed germination; species diversity; virulence; wild plants
• ISSN: 0031-9465; 1593-2095
• DOI: 10.14601/Phytopathol_Mediterr-3152

The distribution and life cycle of wild radish (Raphanus raphanistrum L.) and a survey of the pathogens of this plant are reported for the northern regions of Tunisia. Wild radish is a common weed of cereal crops and legumes. It germinates in early autumn (October), develops a rosette stage in November to December after which stem growth, fl owering and pod production occur through to May, with pod maturity completed in June. Fungus isolation from the foliar tissues exhibiting disease symptoms showed that wild radish was infected with the fungi Albugo candida, Alternaria spp. including A. brassicicola, and A. raphani, Erysiphe cruciferarum, Stemphylium herbarum, Peronospora parasitica and Phoma lingam. Ascochyta spp., Cercospora armoraciae, Cladosporium cladosporioides and Colletotrichum higginsianum are here reported from wild radish for the first time. Inoculation tests of pathogens on wild radish plants showed that the most injurious fungi were Alternaria raphani and Phoma lingam. The remaining pathogens were weakly to moderately aggressive on this weed. To access the pathogenic effect of fungi spontaneously infecting natural populations of wild radish, the weed was grown in a field experiment with and without the broad-spectrum systemic fungicide Carbendazim. Results showed a statistically significant two-fold decrease in the number and weight of seed pods in the non-treated plants, indicating that the reproductive potential of wild radish was naturally reduced by fungal infection. Foliar pathogenic fungi have a potential in the integrated weed management of wild radish, this role merits further investigations.