Blowin’ in the Wind: Wind Dispersal Ability of Phytopathogenic Fusarium in a Wind Tunnel Experiment

Dispersal processes play an essential role in cereal diseases caused by phytopathogenic Fusarium. However, most empirical studies of Fusarium spore dispersal have focused on vertical transport by rain splash, while wind dispersal has been mostly neglected. Our objective was to determine the ability of Fusarium conidiospores to disperse via wind under controlled conditions in a wind tunnel study. Ten Fusarium species with diverse spore varieties were studied by placing them in the wind stream at wind velocities of 5 and 8 m s−1 and collecting them after 6 m and a period of 1 h using a newly developed air sampling box. Although spore concentrations were high in the releasing Petri Dishes, the tested isolates were recaptured in only 18 of 78 runs. F. equiseti and F. cerealis were the most frequently recovered species. Changing abiotic conditions, wind speed, and spore shapes had no significant effect on Fusarium spore recapture rates. Another experiment showed that conidiospores were rarely released from the grown mycelium. Therefore, the importance of wind alone as a dispersal medium for Fusarium conidiospores may have been overestimated so far. Further studies should investigate the importance of carrier media or mobile linkers combined with the wind dispersal of spores.

The morphometric of lycopsid sporophylls and the evaluation of their dispersal potential: an example from the Upper Devonian of Zhejiang Province, China

Background Previous studies have discussed the special structural adaptations of Late Palaeozoic lycopsids, for example, the dispersal potential of reproductive organs. Based on materials from the Upper Devonian Wutong Formation in Changxing County, Zhejiang Province, China, we now analyze the morphometric and perform some calculation to evaluate the dispersal of sporophyll units of lycopsids. Results The fossil sporophyll units are divided into two types in view of obvious difference in shape and we name two new (form) species for them. We also analyze the falling process and give the calculation method of dispersal distance. Conclusions The fossil sporophyll units show relatively poor potential of wind dispersal compared with modern samaras, and show potential adaptation to the turbulent environment.

High matrix vegetation decreases mean seed dispersal distance but increases long wind dispersal probability connecting local plant populations in agricultural landscapes

The authors have requested that this preprint be withdrawn due to a need to make corrections.

Podosphaera spiraeae (Japanese spiraea powdery mildew).

Podosphaera spiraeae is a common fungal pathogen for plants in the genus Spiraea. The pathogen is native to Japan but is most likely widespread throughout the temperate world where viable host plants occur. Identification of powdery mildew on Spiraea spp. can be difficult and its occurrence has not been well documented. Wind dispersal of asexual spores, known as conidia, spreads powdery mildew between viable host plants. The most likely long-distance pathway of invasion is through the nursery industry, which commonly trades Spiraea plants. P. spiraeae can be detrimental to nursery growers as it is unsightly, reduces photosynthesis and flower vigour and causes premature leaf drop. Primary control of the pathogenic fungus requires intricate integrated pest management regimes.

Podosphaera spiraeae (Japanese spiraea powdery mildew).

Podosphaera spiraeae is a common fungal pathogen for plants in the genus Spiraea. The pathogen is native to Japan but is most likely widespread throughout the temperate world where viable host plants occur. Identification of powdery mildew on Spiraea spp. can be difficult and its occurrence has not been well documented. Wind dispersal of asexual spores, known as conidia, spreads powdery mildew between viable host plants. The most likely long-distance pathway of invasion is through the nursery industry, which commonly trades Spiraea plants. P. spiraeae can be detrimental to nursery growers as it is unsightly, reduces photosynthesis and flower vigour and causes premature leaf drop. Primary control of the pathogenic fungus requires intricate integrated pest management regimes.

Wind Dispersal of Natural and Biomimetic Maple Samaras

Maple trees (genus Acer) accomplish the task of distributing objects to a wide area by producing seeds, known as samaras, which are carried by the wind as they autorotate and slowly descend to the ground. With the goal of supporting engineering applications, such as gathering environmental data over a broad area, we developed 3D-printed artificial samaras. Here, we compare the behavior of both natural and artificial samaras in both still-air laboratory experiments and wind dispersal experiments in the field. We show that the artificial samaras are able to replicate (within one standard deviation) the behavior of natural samaras in a lab setting. We further use the notion of windage to compare dispersal behavior, and show that the natural samara has the highest mean windage, corresponding to the longest flights during both high wind and low wind experimental trials. This study demonstrated a bioinspired design for the dispersed deployment of sensors and provides a better understanding of wind-dispersal of both natural and artificial samaras.

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

We analyzed air dispersal of the protistan phyla Cercozoa and Oomycota with an air sampler near the ground (~2 m) and in tree crowns (~25 m) of three tree species (oak, linden and ash) in a temperate floodplain forest in March (before leafing) and May (after leaf unfolding) with a cultivation-independent high throughput metabarcoding approach. Both, Cercozoa and Oomycota, contain important pathogens of forest trees and other vegetation. We found a high diversity of Cercozoa and Oomycota in air samples with 122 and 81 OTUs, respectively. Especially oomycetes showed a high temporal variation in beta diversity between both sampling dates. Differences in community composition between air samples in tree canopies and close to the ground were however negligible, and also tree species identity did not affect communities in air samples, indicating that the distribution of protistan propagules through the air was not spatially restricted in the forest ecosystem. OTUs of plant pathogens, whose host species that did not occur in the forest, demonstrate wind dispersal of propagules from outside the forest biome. Overall, our results lead to a better understanding of the stochastic processes of wind dispersal of protists and protistan pathogens, a prerequisite to understand the mechanisms of their community assembly in forest ecosystems.ImportanceWind dispersal has been shown to play a crucial role in protistan community assembly. The protistan taxa Cercozoa and Oomycota contain important plant parasites with a major ecologic and economic impact. However, comprehensive assessments of cercozoan and oomycete diversity in forest air samples were lacking. Using a cultivation-independent high throughput metabarcoding approach, we analyzed cercozoan and oomycete air dispersal in forest floors and the canopy region – a potential filter for microbial propagules. Our study provides insights into the diversity and community assembly of protists within the air, contributing to a better understanding which factors drive the distribution of plant pathogens within forest ecosystems.

Funtumia elastica (west African rubber tree).

Funtumia elastica is a medium-sized rubber tree native to tropical West Africa. It is considered an invasive species in forest understorey and naturally disturbed areas in Samoa and Martinique. It produces an immense quantity of seeds that are adapted for wind dispersal and its establishment has been favoured by fire and cyclones or hurricanes on these islands. This species can form monospecific stands, outcompeting native species. In some of its native habitats in Africa, F. elastica is a rare canopy species of primary and secondary forests, even being considered an endangered species in some Nigerian forests.