Pest attack-order changes plant defenses

Date:
August 10, 2021
Source:
Washington State University
Summary:
The dining time of different insects impacts a plant's defenses
and nutritional quality -- a complexity uncovered in new research
with implications for pest management strategies.



FULL STORY ==========================================================================
The dining time of different insects impacts a plant's defenses and
nutritional quality -- a complexity uncovered in new research with
implications for pest management strategies.


==========================================================================
A piercing-sucking, virus-carrying aphid has long worried pea plant
farmers, but a more innocuous-seeming weevil that only takes tiny
bites from leaves was found to also play a significant role in plant
health. Depending if the weevils eat before, or after, the aphids,
they can increase or decrease the plant's ability to fend off the virus.

While many studies have focused on the impacts of a single pest, this
study, published Aug. 4 online in Molecular Ecology, is one of the
few to look at the interaction of several antagonists, in this case,
two pests and a virus.

"Plants in the field have a chance of being exposed to many different
types of biotic stress elements, what we call antagonists," said Saumik
Basu, a WSU post-doctoral fellow and the study's lead author. "Based on
how these antagonists are coming to the plants, that can change the plant responses and ultimately leads to changes in their overall productivity." Through a set of greenhouse experiments, Basu and colleagues from the
Crowder Laboratory at WSU and Cornell University attempted to understand
what happens to the pea plant fields of Eastern Washington's Palouse
area. In the field, plants face alternating infestations of pea leaf
weevils, Sitona lineatus, and pea aphids, Acrythosiphon pisum, and
a pathogen the pea aphids are also known to carry, Pea enation mosaic
virus, or PEMV.

The researchers created experiments where first the weevils feasted on
the plants then the aphids, and others that reversed the order. They
also included scenarios where the plants were infected with the virus
and some where they did not as well as a control group.



========================================================================== After removing the pests, the researchers let the plants grow for a
week. Then, they ran plant samples through different sets of analyses to
assess the plants' defense hormone levels and associated defense genes
as well as nutritional qualities.

They found that when the weevil feasts first on the pea plants, it
enhances some of the plants' anti-pathogen defense responses, helping
them become more resilient to a virus infection.

If the weevil dines second, after the aphids, it usually reduces the anti- pathogen defense responses, so the virus spreads more easily.

In turn, virus-infected plants had stronger anti-herbivore responses,
putting out compounds that interfere with the plant-eating pests.

Further complicating the issue, the study found that when the weevils
helped induce the anti-pathogen responses it lowered the nutrition of
the plant by reducing the plants' available amino acids.



========================================================================== These complex interactions hold important implications for pest
management, Basu said.

"If we know beforehand when these interactions are happening, that
information gives farmers a best possible remedy to prevent their fields
from the attack," he said. "This kind of information is really important
for designing sustainable pest and pathogen management strategies."
This study is part of a series of investigations into the interactions
among many organisms that plants encounter. An earlier study in Functional Ecology looked at the antagonism between a plant virus and nitrogen-fixing bacteria called rhizobia that live in the soil. An upcoming study looks
at the interaction between the weevils and rhizobia.

These complex relationships are critical to understanding plant responses,
said Basu.

"In a natural environment, a plant is exposed to different types of
organisms, not just one or two, but many," he said. "The order and the complexity -- how many there are, what different types there are and their interactions -- affect how the plant responds to all these attackers." ========================================================================== Story Source: Materials provided by Washington_State_University. Original written by Sara Zaske. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Saumik Basu, Robert E. Clark, Sayanta Bera, Clare L. Casteel,
David W.

Crowder. Responses of pea plants to multiple antagonists are
mediated by order of attack and phytohormone crosstalk. Molecular
Ecology, 2021; DOI: 10.1111/mec.16103 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210810104646.htm

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