.2019 Mar 12;116(11):4917-4922.

doi: 10.1073/pnas.1820318116. Epub 2019 Feb 25.

Vortex-induced dispersal of a plant pathogen by raindrop impact

Seungho Kim¹, Hyunggon Park², Hope A Gruszewski³, David G Schmale 3rd³, Sunghwan Jung⁴

Affiliations

¹ Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY 14853.
² Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061.
³ School of Plant and Environmental Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061.
⁴ Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY 14853; sunnyjsh@cornell.edu.

PMID:30804195
PMCID: PMC6421443
DOI: 10.1073/pnas.1820318116

Vortex-induced dispersal of a plant pathogen by raindrop impact

Seungho Kim et al. Proc Natl Acad Sci U S A.2019.

.2019 Mar 12;116(11):4917-4922.

doi: 10.1073/pnas.1820318116. Epub 2019 Feb 25.

Authors

Seungho Kim¹, Hyunggon Park², Hope A Gruszewski³, David G Schmale 3rd³, Sunghwan Jung⁴

Affiliations

¹ Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY 14853.
² Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061.
³ School of Plant and Environmental Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061.
⁴ Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY 14853; sunnyjsh@cornell.edu.

PMID:30804195
PMCID: PMC6421443
DOI: 10.1073/pnas.1820318116

Abstract

Raindrop impact on infected plants can disperse micron-sized propagules of plant pathogens (e.g., spores of fungi). Little is known about the mechanism of how plant pathogens are liberated and transported due to raindrop impact. We used high-speed photography to observe thousands of dry-dispersed spores of the rust fungusPuccinia triticina being liberated from infected wheat plants following the impact of a single raindrop. We revealed that an air vortex ring was formed during the raindrop impact and carried the dry-dispersed spores away from the surface of the host plant. The maximum height and travel distance of the airborne spores increased with the aid of the air vortex. This unique mechanism of vortex-induced dispersal dynamics was characterized to predict trajectories of spores. Finally, we found that the spores transported by the air vortex can reach beyond the laminar boundary layer of leaves, which would enable the long-distance transport of plant pathogens through the atmosphere.

Keywords: air vortex; drop impact; dry rust spore; plant pathogen; swirling trajectory.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflicts of interest.

Figures

**Fig. 1.**
(A) Rust-infected wheat leaf surface (*Left*) and SEM image of a uredinium (rust pustule containing urediniospores) (*Right*). Here, a pustule of spores is seen on the epidermis of the wheat leaf. (B) Dispersal of thousands of dry spores by drop impact when [ $R_{d}$ , $U_{d}$ ] $=$ [1.6 mm, 2.4 m/s], where $R_{d}$ , $U_{d}$ are the radius and velocity of the impacting drop, respectively. (C) Visualization of dispersal patterns at [ $R_{d}$ , $U_{d}$ ] $=$ [1.8 mm, 2.8 m/s]. (*Inset*) Dry-dispersed spores discharged by drop impact. (D) The number $N_{s}$ and (E) dispersal distance $D_{d i s p}$ of dry spores versus impact velocity $U_{d}$ for a drop of 1.8-mm radius. The gray area inE corresponds to the calculated distance of dispersed spores without an air vortex. The filled bars and circles are for single spores only, whereas the open bars and circles are for all spores including spore agglomerates (more than one spore).

**Fig. 2.**
(A) Visualization of spores of $P . t r i t i c i n a$ motions moving around a wheat leaf when a raindrop of [ $R_{d}$ , $U_{d}$ ] $=$ [1.6 mm, 2.4 m/s] impacts the leaf surface. Dry-dispersed wheat spores escape from the leaf, showing swirling trajectories during their dispersal (a solid curve with circles is obtained by tracking one spore). Each inset shows overlapping multiple images to visualize the trajectories of dry-dispersed spores (Movies S1 andS2). (B) Comparison of spore trajectories obtained from an experiment and from a ballistic model.

**Fig. 3.**
Visualization of the dispersal motion of glass beads (surrogates for spores) when [ $R_{d}$ , $U_{d}$ ] $=$ [1.9 mm, 3.1 m/s]. Ballistic motion of the beads was observed only at the beginning stage of dispersal, but later spores exhibited a swirling motion (Movies S3 andS4).

**Fig. 4.**
(A) Smoke visualization of the air vortex with [ $R_{d}$ , $U_{d}$ ] = [1.4 mm, 3.3 m/s]. The white dashed curve represents the final shape of a drop and the solid curve indicates the intermediate shape of a spreading drop at the maximum spreading radius. (B) Schematic of the formation of an air vortex, driving spores to swirl around. (C) Magnitude of a circulation $Γ$ versus an impact velocity $U_{d}$ depending on a drop radius $R_{d}$ . (D) $Γ$ is replotted according to our scaling law (Eq.2). (E) Contour map of a vorticity obtained from particle image velocimetry (PIV) measurements using glass beads with [ $R_{d}$ , $U_{d}$ ] $=$ [1.9 mm, 3.1 m/s], showing the dissipation of the air vortex with elapsed times (seeSI Appendix, section D).

**Fig. 5.**
Experimental (circles) and theoretical (solid lines) footprints of glass beads, where [ $R_{d}$ , $U_{d}$ ] = [1.4 mm, 3.2 m/s]. (*Inset*) The actual trajectories of glass beads I, obtained from overlapping multiple images from $t$ = 0.4 to 76 ms.

See this image and copyright information in PMC

References

1. Strange RN, Scott PR. Plant disease: A threat to global food security. Annu Rev Phytopathol. 2005;43:83–116. - PubMed
1. Park RF. Stem rust of wheat in Australia. Aust J Agric Res. 2007;58:558–566.
1. Gilet T, Bourouiba L. Fluid fragmentation shapes rain-induced foliar disease transmission. J R Soc Interface. 2015;12:20141092. - PMC - PubMed
1. Cevallos-Cevallos JM, Danyluk MD, Gu G, Vallad GE, Van Bruggen AHC. Dispersal of salmonella typhimurium by rain splash onto tomato plants. J Food Prot. 2012;75:472–479. - PubMed
1. Geagea L, Huber L, Sache I. Dry-dispersal and rain-splash of brown (Puccinia recondita f. sp. tritici) and yellow (p. striiformis) rust spores from infected wheat leaves exposed to simulated raindrops. Plant Pathol. 1999;48:472–482.

Publication types

Actions

MeSH terms

Actions
Actions
Actions
Actions
Actions
Actions
Actions
Actions
Actions
Actions
Actions
Actions
Actions

LinkOut - more resources

Full Text Sources

Movatterモバイル変換

Account

Save citation to file

Email citation

Add to Collections

Add to My Bibliography

Your saved search

Create a file for external citation management software

Your RSS Feed

Full text links

Actions

Vortex-induced dispersal of a plant pathogen by raindrop impact

Affiliations

Vortex-induced dispersal of a plant pathogen by raindrop impact

Authors

Affiliations

Abstract

Conflict of interest statement

Figures

References

Publication types

MeSH terms

LinkOut - more resources

Full Text Sources