Host and abiotic constraints on the distribution of the pine fungal pathogen Sphaeropsis sapinea (= Diplodia sapinea)

Abstract

Plant fungal pathogens are an increasing emerging threat as climate change progresses. Sphaeropsis sapinea (syn. Diplodia sapinea), the causal fungal agent of Diplodia tip blight, is a major pathogen of pines of forestry and ornamental relevance in Europe and worldwide. Here, we combined molecular-based field surveys in a common-garden setting and across an elevation gradient with historical records, cultivation-based growth experiments and microscopy to report on host and abiotic constraints on the distribution of S. sapinea. Using the arboretum at the Botanical Garden Berlin, Germany, to control for environmental variability, S. sapinea was detected on all seven host Pinus species we studied. However, P. sylvestris is the only species in which the fungus was detected in symptomless needles at the arboretum, and the most frequently recorded host for over a century, suggesting that it is the main, and perhaps, potential original host. In addition, sampling symptomatic needles in four out of the seven same species across a gradient from 200 to 2,100 m of elevation in the French Alps, S. sapinea was not detected at elevation higher than 800 m. Abiotic constraints were also supported by reduced growth of isolates of S. sapinea at low temperature under controlled conditions, but a 35°C prior stress exposure increased the subsequent growth of S. sapinea within its optimal temperature range (20-30°C). Altogether, our study thus not only suggests that S. sapinea is more likely to cause tip blight in P. sylvestris compared to the other species we studied, but also that in the current context of global climate change with predicted temperature increases, the fungus could infect a wider range of pine hosts and locations worldwide.

Fungi associated with shoot dieback of Pinus mugo subsp. mugo in the Polish Tatra Mountains

“…Diplodia sapinea is also widely distributed in Poland, one of the most common agents of the apical dieback of pine shoots, and the main cause of the blue stain of P. sylvestris in Poland (Jankowiak et al, 2021). The sporadic presence of D. sapinea on P. mugo in subalpine areas of the Tatra Mountains is consistent with the results of Fabre et al (2011) and Roy et al (2022). According to these authors, disease severity decreases with increasing elevation (in particular above 800 m elevation), possibly because of low temperature (especially mean daily minimum temperature in winter).…”

“…(2011) and Roy et al. (2022). According to these authors, disease severity decreases with increasing elevation (in particular above 800 m elevation), possibly because of low temperature (especially mean daily minimum temperature in winter).…”

“…Interestingly, another pathogen of pine, D. sapinea , was sporadically isolated in the present study. In Europe, this fungus infects many species of pines, including P. mugo , which is known to be susceptible to Diplodia tip blight (Blumenstein, Bußkamp, Langer, Langer, et al., 2021; Fabre et al., 2011; Roy et al., 2022). Diplodia sapinea is also widely distributed in Poland, one of the most common agents of the apical dieback of pine shoots, and the main cause of the blue stain of P. sylvestris in Poland (Jankowiak et al., 2021).…”

“…Fungal diseases of P. mugo have been poorly studied, although several well‐known pathogens have been reported to induce needle, shoot, and root disease in P. mugo (e.g. Bartnik et al., 2021; Bendel et al., 2006; Donaubauer, 1972; Drenkhan et al., 2016; Koukol et al., 2015; Kowalski et al., 2018; Nest et al., 2019; Pusz et al., 2013; Roy et al., 2022; Senn, 2009). The most important foliar pathogens of P. mugo are Lecanosticta acicola (Thüm.)…”

“…Less is known about pathogens of P. mugo shoots, as the only reported pathogens are Gremmeniella abietina (Lagerberg) Morelet, which causes Scleroderris canker and Diplodia sapinea (= Sphaeropsis sapinea (Fr.) Dyko & B. Sutton), which causes Diplodia tip blight (Blumenstein et al., 2022; Blumenstein, Bußkamp, Langer, Langer, et al., 2021; Donaubauer, 1972; Roy et al., 2022). Gremmeniella abietina causes shoot dieback and cankers and can cause tree death (Butin, 1995; Kowalski, 1983).…”