Sirococcus clavigignenti-juglandacearum: An Undescribed Species Causing Canker on Butternut

Reclassification of the butternut canker fungus, Sirococcus clavigignenti-juglandacearum, into the genus Ophiognomonia

“…cordiformis and J. cinerea was observed in late spring as healthy buds begin to swell and open, however, infected buds fail to open and begin to turn dark reddish brown and then black and infection progresses down the stem turning it a reddish brown (Fig 4). In addition to the description given by Nair et al (1979) of the fungus in culture, the authors have observed three other frequently recovered phenotypes . The four phenotypes observed were: A) light coloured mycelium, concentric rings, sporulating, and no pigmentation of the agar (L, R, Sp); B) sectored (both dark and light mycelium), concentric rings, sporulating, and no pigmentation of the agar (Sec, R, Sp); C) dark mycelium, concentric rings, sporulating, and dark pigmentation of the agar (Dk, R, Sp,); or D) dark, slow growing with thin or diffuse mycelium, and dark pigmentation of the agar (Dk, D).…”

“…The four phenotypes observed were: A) light coloured mycelium, concentric rings, sporulating, and no pigmentation of the agar (L, R, Sp); B) sectored (both dark and light mycelium), concentric rings, sporulating, and no pigmentation of the agar (Sec, R, Sp); C) dark mycelium, concentric rings, sporulating, and dark pigmentation of the agar (Dk, R, Sp,); or D) dark, slow growing with thin or diffuse mycelium, and dark pigmentation of the agar (Dk, D). Phenotype C was the culture morphology described by Nair et al (1979).…”

“…In recent years, the tree has been decimated by this fungal pathogen, with reports indicating declines of as much as 70e90 % in some regions (Anderson & LaMadeleine 1978). Butternut canker was first reported from southwestern Wisconsin in 1967 (Renlund 1971) and the pathogen causing the disease was first described in 1979 (Nair et al 1979). The pathogen grows under the bark layer after the spores have found an entry point, where it forms a thin, black stromatic tissue under the bark, and eventually produces a number of stromatal columns composed of interwoven mycelia, which lifts the dying bark layers of the tree until it ruptures (Tisserat & Kuntz 1984).…”

Estimating heritability of disease resistance and factors that contribute to long-term survival in butternut (Juglans cinerea L.)

“…A stem canker disease of butternut caused by the ascomycete fungus Ophiognomonia clavigignenti-juglandacearum (Oc-j) (=Sirococcus clavigignenti-juglandacearum) (Broders and Boland 2011) was first reported in the late 1960s (Renlund 1971), although it was most likely introduced decades prior in some areas (Broders et al 2012(Broders et al , 2014. Cankers generally initiate in small crown branches, spreading to main limbs and the trunk (Nair et al 1979;Ostry and Woeste 2004) and causing mortality either when cankers coalesce to girdle the stem or when secondary decay results in breakage or windfall. Incidence of canker disease is near 100 % in most of butternut's range and mortality rates are as high as 90 % (Schultz 2003), but monitoring has revealed that a few trees in areas of high disease incidence have survived and remained vigorous or, in rare cases, largely free of cankers.…”

Ecological impacts of non-indigenous invasive fungi as forest pathogens

“…However, in 1967, a previously unknown fungus, Sirococcus clavigignenti-juglandacearum was found to be the causal agent for butternut canker (Renlund 1971). The role and taxonomy of S. clavigignenti-juglandacearum was not fully understood until after extensive research and determination that the fungus merited description as a new taxon in 1979 (Nair et al 1979). The origin of the species is not known but it is thought likely to be non-indigenous in North America because of its sudden appearance, its aggressiveness, and the lack of genetic variability (Furnier et al 1999).…”