First report of Fusarium proliferatum causing fusarium root disease on sugar pine (Pinus lambertiana) in a forest Container nursery in California.
In June 2015, approximately 30% of 2 seedlots of sugar pine (P. lambertiana) seedlings (∼1300 of 4400 total seedlings) growing in a container forest nursery in California (USA) showed classic symptoms of Fusarium root disease: needle chlorosis, needle tip/twig dieback, foliar/branch/stem necrosis, and root decay. Root tips of symptomatic sugar pine seedlings were surface disinfested in 1% sodium hypochlorite solution for 10 to 20 s, washed in distilled water, dried on sterile filter paper, placed onto Komada medium, and incubated at 22°C for 3 to 7 days. Pure cultures were obtained by single hyphal tip transfers on potato dextrose agar medium. Based on morphological characteristics, sequence analysis of the translation elongation factor-1α gene and pathogenicity tests, the causal agent was identified as F. proliferatum. This is thought to be the first report of F. proliferatum on sugar pine in North America, although this pathogen is frequently associated with other conifer seedlings in nurseries across the USA.