02140nas a2200169 4500008004100000022003100041245012500072210006900197260001600266300002000282520151300302100002601815700001901841700002001860700002401880856006601904 2019 eng d a0191-2917 e-ISSN:1943-769200aVariation in Susceptibility of Tanoak to the NA1 and EU1 Lineages of Phytophthora ramorum, the Cause of Sudden Oak Death0 aVariation in Susceptibility of Tanoak to the NA1 and EU1 Lineage cFeb-09-2021 aPDIS-04-19-08313 a

Phytophthora ramorum, the cause of sudden oak death (SOD), kills tanoak (Notholithocarpus densiflorus) trees in southwestern Oregon and California. Two lineages of P. ramorum are now found in wildland forests of Oregon (NA1 and EU1). In addition to the management of SOD in forest ecosystems, disease resistance could be used as a way to mitigate the impact of P. ramorum. The objectives of this study were to (i) characterize the variability in resistance of N. densiflorus among families using lesion length; (ii) determine whether lineage, isolate, family, or their interactions significantly affect variation in lesion length; and (iii) determine whether there are differences among isolates and among families in terms of lesion length. The parameters isolate nested within lineage (isolate[lineage]) and family × isolate(lineage) interaction explained the majority of the variation in lesion length. There was no significant difference between the NA1 and EU1 lineages in terms of mean lesion length; however, there were differences among the six isolates. Lesions on seedlings collected from surviving trees at infested sites were smaller, on average, than lesions of seedlings collected from trees at noninfested sites (P = 0.0064). The results indicate that there is potential to establish a breeding program for tanoak resistance to SOD and that several isolates of P. ramorum should be used in an artificial inoculation assay.

1 aSøndreli, Kelsey, L.1 aKanaskie, Alan1 aKeriö, Susanna1 aLeBoldus, Jared, M. uhttps://apsjournals.apsnet.org/doi/10.1094/PDIS-04-19-0831-RE