First Report of Heterobasidion occidentale on Sequoia sempervirens in Northern California

Abstract

In 2007, Heterobasidion basidiocarps (“fruit bodies”) were found on 37 of 200 coast redwood (Sequoia sempervirens) stumps surveyed in four stands owned by the Green Diamond Resource Company near McKinleyville, CA (Humboldt County). All were second or third growth stands, last logged 7-13 years prior to the survey here described. In 2015, during a second follow-up survey, 10 fruit bodies and two rotted wood samples were collected from 10 separate stumps, their DNA was extracted, and the Internal Transcribed Spacer was amplified and sequenced using the ITS1f-ITS4b primers described by Gardes and Bruns (1993). All sequences (e.g. GenBank Accession No. MF488718) had a 99-100% homology with ITS sequences of Heterobasidion occidentale (e.g. Accession No. KC492946), a widespread root and butt rot agent common on Abies, Picea, and Tsuga spp. in western North America, and also found on Sequoiadendron giganteum in the Central Sierra Nevada (Garbelotto and Gonthier 2013). Sapwood in 97% (range 96-100%) of the 200 st...