Do colonization by dark septate endophytes and elevated temperature affect pathogenicity of oomycetes?

Abstract

Phialocephala subalpina is one of the most frequent dark septate root endophytes in tree roots but its function in forest ecosystems is largely unknown. A full-factorial infection experiment was performed, using six P. subalpina isolates, two pathogenic oomycetes (Phytophthora plurivora [syn. Phytophthora citricola s.l.] and Elongisporangium undulatum [syn. Pythium undulatum]) and two temperature regimes (17.9 and 21.6°C) to examine the ability of P. subalpina to protect Norway spruce seedlings against root pathogens. Seedling survival, disease intensity and seedling growth were affected by P. subalpina genotype, temperature and pathogen species. Some P. subalpina isolates effectively reduced mortality and disease intensity caused by the two pathogens. Elevated temperature adversely affected seedling growth but did not aggravate the effect of the pathogens. Elongisporangium undulatum but not P. plurivora significantly reduced plant growth. Colonization density of P. subalpina measured by quantitative PCR was not affected by temperature or the presence of the pathogens. In conclusion, P. subalpina confers an indirect benefit to its host and might therefore be tolerated in natural ecosystems, despite negative effects on plant health and plant growth.

Communities of Cultivable Root Mycobionts of the Seagrass Posidonia oceanica in the Northwest Mediterranean Sea Are Dominated by a Hitherto Undescribed Pleosporalean Dark Septate Endophyte

“…The tree was rooted with Myriangium hispanicum (Myriangiales) and Dothidea insculpta (Dothideales). For details on the sequences used, see BMaterials and Methods^M may include protection of host roots against pathogen attacks [31] or modifications of the distribution of rhizosphereassociated organisms [59,60] as suggested for other fungi possessing melanized hyphae. Moreover, P. oceanica forms characteristic peat-like sediment (matte) which can be several meters thick and which is exceptionally resistant to decay [1].…”

“…Terrestrial root endophytes may, among other possible functions, engage in nutrient uptake and transport to the host plant [30] and protect host roots against pathogen attacks [31]. On the other hand, nearly nothing is known about possible roles of endophytes in seagrass roots, and this is probably due to both the low number of seagrass mycobiont studies and their differing results.…”

Unraveling the Dark Septate Endophyte Functions: Insights from the Arabidopsis Model

“…Similarly, multiple Phialocephala subalpina strains reduced spruce mortality and severity of oomycete P . citricola and Pythium undulatum diseases (Tellenbach and Sieber 2012 ). Complex interactions among soiland root-inhabiting organisms are likely common.…”

Multigene phylogenetic study of Cyclaneusma species

“…Secondly, the study of inter‐ and intraspecific responses to environmental stimuli such as changing climatic conditions (Fabre et al. ; Sturrock ; Tellenbach and Sieber ) may assist in predicting the likely disease impacts. Thirdly, selection for and deployment of host resistance, chemical control or putative biocontrol agents such as endophytes, also requires a sound knowledge of the pathogen (Ganley et al.…”