Cocklebur (Xanthium stramonium) and sowthistle (Sonchus cornutus) as Host Plants of Vegetables Powdery Mildew

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Gamiel, S.A
Ahmed, N.E.
Ma, Y.Q.
Inanaga, S.
Sugimoto, Y.
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Faculty of Agriculture, University of Khartoum, Shambat, Sudan
A powdery mildew species of tomato and sowthistle (Sonchus cornutus) was identified as Erysiphe sp., based on anamorph characteristics. The pathogen is ectophyte; conidia are ellipsoid and formed singly on unbranched conidiophores; fibrosin bodies were not present, and vacuoles were observed. Tomato was not extensively colonized by Erysiphe sp. compared to Leveillula taurica. Erysiphe sp. is pathogenic to snake cucumber and okra but not cocklebur (Xanthium stramonium), and cross infection was achieved between these host plants. Leveillula taurica was restricted to tomato and okra, whereas Sphaerotheca fuliginea caused powdery mildew of snake cucumber, okra and cocklebur. Reciprocal inoculation between these crops demonstrated cross infectivity, but conidia from cocklebur failed to infect any of the tested plant species except its original host. Sowthistle poses a great risk to tomato production, while cocklebur probably does not have any significant role in natural occurrence of tomato powdery mildew and that of other vegetables.
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