01928nas a2200193 4500008004100000022001400041245010300055210006900158260001600227300001200243490000800255520129500263100002501558700002301583700001701606700002501623700002101648856006501669 2016 eng d a0031-949X00aHost Phenology and Leaf Effects on Susceptibility of California Bay Laurel to Phytophthora ramorum0 aHost Phenology and Leaf Effects on Susceptibility of California  cJan-01-2016 a47 - 550 v1063 a

Spread of the plant pathogen Phytophthora ramorum, causal agent of the forest disease sudden oak death, is driven by a few competent hosts that support spore production from foliar lesions. The relationship between traits of a principal foliar host, California bay laurel (Umbellularia californica), and susceptibility to P. ramorum infection were investigated with multiple P. ramorum isolates and leaves collected from multiple trees in leaf-droplet assays. We examined whether susceptibility varies with season, leaf age, or inoculum position. Bay laurel susceptibility was highest during spring and summer and lowest in winter. Older leaves (>1 year) were more susceptible than younger ones (8 to 11 months). Susceptibility was greater at leaf tips and edges than the middle of the leaf. Leaf surfaces wiped with 70% ethanol were more susceptible to P. ramorum infection than untreated leaf surfaces. Our results indicate that seasonal changes in susceptibility of U. californica significantly influence P. ramorum infection levels. Thus, in addition to environmental variables such as temperature and moisture, variability in host plant susceptibility contributes to disease establishment of P. ramorum.

1 aJohnston, Steven, F.1 aCohen, Michael, F.1 aTorok, Tamas1 aMeentemeyer, Ross, K1 aRank, Nathan, E. uhttp://apsjournals.apsnet.org/doi/10.1094/PHYTO-01-15-0016-R