Species Richness, rRNA Gene Abundance, and Seasonal Dynamics of Airborne Plant-Pathogenic Oomycetes

Abstract

Oomycetes, also named Peronosporomycetes, are one of the most important and widespread groups of plant pathogens, leading to significant losses in the global agricultural productivity. They have been studied extensively in ground water, soil, and host plants, but their atmospheric transport vector is not well characterized. In this study, the occurrence of airborne Oomycetes was investigated by Sanger sequencing and quantitative PCR of coarse and fine aerosol particle samples (57 filter pairs) collected over a 1-year period (2006–2007) and full seasonal cycle in Mainz, Germany. In coarse particulate matter, we found 55 different hypothetical species (OTUs), of which 54 were plant pathogens and 29 belonged to the genus Peronospora (downy mildews). In fine particulate matter (<3 μm), only one species of Hyaloperonospora was found in one sample. Principal coordinate analysis of the species composition revealed three community clusters with a dependence on ambient temperature. The abundance of Oomycetes rRNA genes was low in winter and enhanced during spring, summer, and fall, with a dominance of Phytophthora, reaching a maximum concentration of ∼1.6 × 106 rRNA genes per cubic meter of sampled air in summer. The presence and high concentration of rRNA genes in air suggests that atmospheric transport, which can lead to secondary infection, may be more important than currently estimated. This illustrates the need for more current and detailed datasets, as potential seasonal shifts due to changing meteorological conditions may influence the composition of airborne Oomycetes. An insight into the dynamics of airborne plant pathogens and their major drivers should be useful for improved forecasting and management of related plant diseases.

To the canopy and beyond: Air samples reveal wind dispersal as a driver of ubiquitous protistan pathogen assembly in tree canopies

“…The presence of ~54% of all oomycete OTUs in both sampling events ( Figure 4B) indicates a continuous presence of both peronosporean and pythialean oomycete spores and consequently a high proportion of potentially physiologically active oomycetes, including potential pathogens within forest ecosystems. Oomycetes pose a serious threat to forest health and functioning, it is therefore crucial to better understand their diversity and distribution patterns of the total forest ecosystem, including air samples (Derevnina et al, 2016;Ajchler et al, 2017;Jung et al, 2018;Lang-Yona et al, 2018). We detected no OTUs assigned to the orders Saprolegniales, Lagenidiales or Myzocytiopsidales, even though Jauss et al (2020) found them in canopy and ground samples.…”

“…Wind dispersal is an important means for the distribution of microbial plant pathogens, and oomycetes are no exception (Fawke et al, 2015;Lang-Yona et al, 2018). Yet, comprehensive assessments of their abundances within the forest air were lacking.…”

“…They dominate terrestrial habitats (Urich et al, 2008;Voss et al, 2019) and harbor important plant pathogens, such as the Endomyxa, which have recently been elevated from the Cercozoa into a separate phylum (Cavalier-Smith et al, 2018). Another protistan taxon, the Oomycetes (Stramenopiles), contain important parasites of forest trees, and many lineages produce caducous sporangia for dissemination (Goheen & Frankel, 2009;Robideau et al, 2011;Lang-Yona et al, 2018).…”

Pythium insidiosum Keratitis: Past, Present, and Future

“…The genus Pythium embraces 200 species. They are one of the most destructive plant pathogens, infecting crops and destroying the seeds, storage organs, roots, and other plant tissues [ 1 ]. The genus was considered as true fungi by Pringsheim in 1858 due to characteristics including eukaryotes with filamentous growth, absence of septa, nutrition by absorption, and reproduction via spores [ 2 ].…”

Bioaerosols and atmospheric ice nuclei in a Mediterranean dryland: community changes related to rainfall

“…They comprise living and dead microorganisms (e.g., bacteria), dispersal units (e.g., fungal spores, plant pollen), fragments (e.g., plant debris), and viruses (Després et al, 2012;Whon et al, 2012;Fröhlich-Nowoisky et al, 2016;Smets et al, 2016;Yahya et al, 2019;Pöhlker et al, 2021). Bioaerosols can serve as nuclei for cloud droplets and ice crystals influencing the formation of precipitation, and some of them are important allergens and pathogens (Brown and Hovmøller, 2002;D'Amato et al, 2007;Andreae and Rosenfeld, 2008;Steiner et al, 2015;Müller-Germann et al, 2017;Fröhlich-Nowoisky et al, 2016;Lang-Yona et al, 2018;Huang et al, 2021). The abundance and composition of bioaerosols are determined by local emission sources, meteorological conditions, and long-range transport (Jones and Harrison, 2004;Franzetti et al, 2011;Bowers et al, 2012Bowers et al, , 2013Gandolfi et al, 2013;Cao et al, 2014;Archer et al, 2020).…”