Abstract
Plant pathogens have evolved many dispersal mechanisms, using biotic or abiotic vectors or a combination of the two. Rain splash dispersal is known from a variety of fungi, and can be an efficient driver of crop epidemics, with infectious strains propagating rapidly among often genetically homogenous neighboring plants. Splashing is nevertheless a local dispersal process and spores taking the droplet ride seldom move farther than a few decimeters. In this study, we assessed rain splash dispersal of conidia of the yam anthracnose agent, Colletotrichum gloeosporioides, in an experimental setting using a rain simulator, with emphasis on the impact of soil contamination (i.e., effect of re-splashing events). Spores dispersed up to 50 cm from yam leaf inoculum sources, though with an exponential decrease with increasing distance. While few spores were dispersed via re-splash from spore-contaminated soil, the proportion deposited via this mechanism increased with increasing distance from the initial source. We found no soil contamination carryover from previous rains, suggesting that contamination via re-splashing from contaminated soils mainly occurred within single rains. We conclude that most dispersal occurs from direct splashing, with a weaker contribution of indirect dispersal via re-splash.
Highlights
Aerial dispersal of microbes and fungal spores was described in the late nineteenth century [1] and subsequently developed into its own branch of biologyPLOS ONE | DOI:10.1371/journal.pone.0115757 December 22, 2014Direct Dispersal from Source Prevails over Indirect Rainsplash Spread
Drop number decreased with distance from source (Table 1A; Fig. 2A), and as expected this effect was more pronounced for direct splashing from the inoculum source than for re-splash
Most spore deposition was via direct splashes, even if the difference between direct and indirect dispersal decreased with distance (Fig. 2C)
Summary
Aerial dispersal of microbes and fungal spores was described in the late nineteenth century [1] and subsequently developed into its own branch of biologyPLOS ONE | DOI:10.1371/journal.pone.0115757 December 22, 2014Direct Dispersal from Source Prevails over Indirect Rainsplash Spread (aerobiology; [2],[3]). Wind will increase primary rain dispersal distance in a downwind direction and decrease it upwind, but it is generally accepted that wind dispersal distances are generally longer than rain dispersal alone [12], and that pure splash dispersal is mostly local [13]. Despite this limitation, splash dispersal may still be efficient when host plant species occurs at high densities, and it is especially wellsuited for crop pathogens with large patches of host plants growing in often pure, high-density stands
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