B

arley yellow dwarf virus is an important pathogen

that reduces the yield and grain quality of impor-

tant food crops such as wheat, barley, oats and

corn. We have found that the virus thrives when

wheat is grown in the laboratory at higher carbon

dioxide(CO 2 )levels, resulting in greater plant damage.Our

indings suggestthat asCO 2 concentrations rise to levels

predicted by climate change modellers, food crop plants such

as wheat can be badly affected.

Barley yellow dwarf virus is spread by aphids, which acquire

it from the sap of an infected plant. As the aphids feed on other

plants, they transmit the virus through their saliva. At least 25

species of aphids can successfully transmit this virus between

plants, but the major vector is the bird cherry-oat aphid

(Rhopalosiphum padi), which is found across Australia and

other parts of the world.

A high concentration of the virus in plants causes earlier

and more pronounced symptoms in susceptible varieties. As

insects are attracted to infected plants by sensing changes in

plant colour and odour, this can increase the probability that

the virus will spread.

Wheat plants are most vulnerable to viral infection at the early

growth stage. Infection of wheat with barley yellow dwarf virus

when the plants are a couple weeks old can result in yield losses

of up to 70%. In Australia, this virus affects yields across all

cereal-growing regions of south-west and south-east Australia,

as well as south-east Queensland. Factors such as weather condi-

tions and virus concentrations in weeds and aphids will alter its

impact, but even sporadic outbreaks of barley yellow dwarf

virus can increase the incidence of the virus and therefore reduce

crop yields.

Although plant viral diseases are a serious threat to food

production, only a few studies have investigated how plants

and viruses interact under conditions of elevatedCO 2 concen-

trations or increased temperatures. Instead, most plant studies

have focused on disease-free plants under elevatedCO 2 scenarios,

often without considering temperature increases.

These studies show both positive and negative effects. Posi-

tive effects have included increased yield and improved rates of

photosynthesis, greater light useeiciency andhigher water-use

eiciency due tothe partial closure of stomata. However,

36 | MAY 2016

PPlant Viruses Threaten

Crops as Climate Warms

Wheat grain that is infected with barley yellow dwarf virus (left)

compared with uninfected wheat grain (right).

PIOTR TREBICKI

Climate change will exacerbate the spread of a virus that reduces the yield of infected wheat

by 70%.