10.5061/DRYAD.6DJH9W10J
Krause, Anita
0000-0002-9119-2372
University of Minnesota System
Seabloom, Eric
0000-0001-6780-9259
University of Minnesota
Borer, Elizabeth
University of Minnesota
Shoemaker, Lauren
University of Wyoming
Sieben, Andrew
0000-0003-1615-4306
University of Wyoming
Campbell, Ryan
University of Minnesota
Strauss, Alexander
University of Georgia
Shaw, Allison
0000-0001-7969-8365
University of Minnesota
Data from: Pliant pathogens: Estimating viral spread when confronted with
new vector, host, and environmental conditions
Dryad
dataset
2020
FOS: Biological sciences
pathogen
Barley yellow dwarf virus
transmission
novel conditions
Avena sativa
aphid
National Science Foundation
https://ror.org/021nxhr62
DEB-1556649
2021-12-24T00:00:00Z
2021-01-26T00:00:00Z
en
https://doi.org/10.1002/ece3.7178
23238 bytes
3
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
Pathogen spread rates are determined, in part, by the performance of
pathogens under altered environmental conditions and their ability to
persist while switching among hosts and vectors. To determine the effects
of new conditions (host, vector, and nutrient) on pathogen spread rate, we
introduced a vector-borne, viral plant pathogen, Barley Yellow Dwarf Virus
PAV (BYDV-PAV) into hosts, vectors, and host nutrient supplies that it had
not encountered for thousands of viral generations. We quantified pathogen
prevalence over the course of two serial inoculations under the new
conditions. Using individual level transmission rates from this
experiment, we parameterized a dynamical model of disease spread and
projected spread across host populations through a growing season. A
change in nutrient conditions (increased supply of phosphorus) reduced
viral transmission whereas shifting to a new vector or host species had no
effect on infection prevalence. However, the reduction in the new
nutrient environment was only temporary; infection prevalence recovered
after the second inoculation. Synthesis. These results highlight how
robust the pathogen, BYDV-PAV, is to changes in its biotic and abiotic
environment. Our study also highlights the need to quantify longitudinal
infection information beyond snapshot assessments to project disease risk
for pathogens in new environments.
Natal conditions Our experiment used BYDV-PAV viral cultures that had been
maintained in the laboratory (see Viral Culture Source in Appendix) using
a single aphid species, S. avenae, on a single host species, A. sativa,
under low nutrient conditions for 251 days (see detailed information
regarding vector colony and host plant source in Appendix, Vector
Conditions and Host Conditions). Aphid population growth under these
natal conditions produces approximately 12 generations of S. avenae
(Dedryver et al., 1998), and approximately 1,800 to 6,000 generations of
BYDV-PAV (Yarwood, 1956). Treatment conditions We experimentally exposed
natal viral cultures to a range of conditions consisting of two aphid
vectors, two plant hosts, and four nutrient conditions for a total of 16
treatments. The treatments consisted of a full cross of vector (two
conditions), host (two conditions), and nutrient (four conditions) across
the natal, S. avenae, or new aphid vector, R. padi, the natal, A. sativa,
or new host species, H. vulgare, and the nutrient conditions. The
nutrient conditions included nitrogen (NH4NO3), phosphorus (KH2PO4),
nitrogen plus phosphorus, or no additional nutrients. Each treatment was
repeated eight times over three consecutive temporal blocks for a total 24
replicates per treatment. For each block of the experiment, 70 seeds from
each host plant species were planted for a total of 140 plants. Each
block had eight replicates per treatment with 12 additional seeds planted
to account for the possibility of for failed germinations. The plants
were watered with the four nutrient treatments: nanopure water only
(Control), 10% nitrogen solution, 10% phosphorus solution, or 10% nitrogen
& phosphorus solution all based on a Half-Strength Hoagland’s
solution (Hoagland and Arnon 1950) which are consistent with previous
experiments (Lacroix, Seabloom and Borer, 2014). The first inoculation
that introduced the virus to new biotic and abiotic conditions will be
referred to as Round 1. We then performed a second inoculation (referred
to as Round 2) in vivo such that all treatments were applied to a set of
hosts that maintained the treatment where plant tissue from Round 1
treatments was used to infect the aphids used in Round 2. A simple
schematic depicting the inoculation and treatment conditions is
represented in Fig. 1. Assessing viral evolution and population dynamics
after serial passages is not uncommon (Sylvester, Richardson and Frazier,
1974; Kurath and Palukaitis, 1990; Schneider and Roossinck, 2000; Bartels
et al., 2016) but quantifying virus transmission in serially passaged
viruses after switching abiotic or biotic conditions has rarely been
performed. All plant tissues were collected between June 5th, 2017 and
October 10, 2017. All plant tissue was collected and preserved at -20C
for molecular processing. Virus inoculation Each block as described under
Treatment Conditions, included two inoculation rounds. During the first
inoculation (Round 1) of the experiment, 360 live, adult-sized aphids of
both R. padi and S. avenae were removed from uninfected plants and
transferred to 25ml cork sealed tubes (24x) each containing 30 aphids of
the same species. Leaf tissue from approximately four-week-old plants
confirmed to be infected with BYDV-PAV was clipped and 4-6 cm of infected
tissue was transferred into each tube containing non-viruliferous aphids.
Aphids remained in cork sealed tubes for 48 hours such that they became
viruliferous from feeding on infected plant tissue, meaning the aphids
were then able to transmit the virus. After 48 hours, aphids were moved to
uninfected plants for the initial inoculation period. Plants used for the
initial inoculation were uninfected prior to aphid exposure as the plants
remained isolated from aphids and other insects and there is no evidence
of vertical transmission of BYDV-PAV in hosts. We controlled for factors
known to influence transmission efficiency including length of feeding
period on infected tissue and age of host tissue (Gray et al., 1991). To
do this, a single 2.5 x 8.5 cm, 118 μm polyester mesh cage was attached to
the oldest leaf on each 17-day old experimental plant. Five viruliferous
aphids were transferred into each polyester mesh cage which was then
sealed. The experimental plants containing the caged aphids were then
placed in a growth chamber and aphids fed for approximately 96 hours,
after which the aphids were killed to end transmission. At the start of
the second inoculation (Round 2), the experimental plants from Round 1
were destructively harvested and the polyester mesh cages were removed.
Each 8.5 cm leaf enclosed by the cage was cut from the plant and
transferred to a clean 25 ml tube while the above-ground plant tissue was
stored at -20C. Once all tissues were collected at the end of the
experiment, BYDV-PAV infection status (presence/absence) was assessed
using polymerase chain reaction (see Virus detection in Appendix). Ten
aviruliferous aphids (i.e., not yet carrying a virus) of each species were
collected from vector source conditions, transferred into each of the
tubes respective to the treatment, and allowed to feed for 48-hours. Five
aphids from each tube were transferred to a new experimental plant raised
under the treatment conditions and cage-sealed; the remaining five aphids
were discarded. During Round 2, the treatments with R. padi in the sixth
block only contained one aphid per cage due to R. padi colony depletion.
All other treatments contained five aphids per cage per block. The
experimental plants were subjected to feeding period of 96 hours after
which the aphids were killed. BYDV-PAV infection status
(presence/absence) was assessed using polymerase chain reaction (see Virus
detection in Appendix).