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Solanaceous weeds as potential hosts for new clonal lineages of Phytophthora infestans.
A. C. SEIDL (1), A. J. Gevens (1). (1) University of Wisconsin, Madison, WI, U.S.A.

Weed hosts of <i>Phytophthora infestans</i> in the US have been noted, but the potential of new clonal lineages to infect common solanaceous weeds, which may influence the epidemiology of potato and tomato late blight, has not been elucidated. Representative isolates of the clonal lineages US-22, US-23, and US-24 collected in WI in 2009 and 2010 were used to inoculate wounded or intact fruits and detached leaves of black nightshade (NS), hairy NS, bittersweet NS and ‘Juliet’ tomato. Sporulation incidence on fruit was low for all hosts and lineages, except for wounded black NS fruits inoculated with US-22 (39%). This overall low fruit incidence may still be important due to the large number of fruits produced and their ability to persist beyond foliage senescence. Mycelial density, averaged across lineages, was low on infected black NS and bittersweet NS leaves (<17%) but high on hairy NS (89%), which was statistically similar to tomato. To further compare hosts, sporangial production by US-22, US-23, and US-24 on leaf disks of ‘Brandywine Red’ tomato, ‘Katahdin’ potato and hairy NS was quantified. On hairy NS sporangial production by US-23 was significantly greater than by US-24, but across lineages was not significantly different than potato. This work demonstrates the potential of new clonal lineages of <i>P. infestans</i> to infect and sporulate on fruits and leaves of common solanaceous weeds, which may have important epidemiological consequences for late blight management.<p><p>Keywords: Oomycete, Root-Tuber Crops, Potato

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