Pests and diseases

Pests and diseases

Background

Crown rot and barley yellow dwarf virus are major diseases of Australian cereal crops, causing significant losses in the grains industry. The industry faces considerable uncertainty around how elevated carbon dioxide (eCO2), higher temperatures and extreme climate events will influence pathogen prevalence, insect behaviour and interactions with the crop.

Project outline

Crown rot

Wheat lines were grown at the AGFACE facility under ambient CO2 (384 μmol/mol) and eCO2 (550 μmol/mol) to determine if eCO2 influenced the severity of the fungal disease crown rot (CR), the resistance to the disease across genotypes, and disease interactions with grain yield and quality.

Barley yellow dwarf virus

A series of experiments were conducted in growth chambers, greenhouses and the AGFACE facility to determine the impact of eCO2 on the aphid Rhopalosiphum padi (R. padi), which is the main vector of barley yellow dwarf virus (BYDV) in southern Australia.

Results

Crown rot

Crown rot will remain a significant challenge to wheat production and may become more severe under eCO2 conditions:

  • Stem browning and CR severity were increased under eCO2 but this varied across genotypes
  • Frequency of highly aggressive strains of the CR fungal pathogen increased under eCO2
  • Grain yield of infected plants was reduced more under eCO2 than under current ambient conditions
  • The level of the fungal mycotoxin deoxynivalenol in wheat crowns was increased under eCO2, potentially providing health risks to stock feeding on infected grains
  • Partially resistant wheat lines remained resistant under eCO2 indicating that resistance traits will still be useful in the future when developing new resistant varieties adapted to higher atmospheric CO2 conditions.

Barley yellow dwarf virus

BYDV and its aphid vector are expected to increase in severity under future climates with increased CO2 and temperatures:

  • Plant leaf nitrogen content decreases under eCO2, making plants less nutritious for aphids, causing them to compensate by feeding longer
  • Under eCO2 BYDV infected plants do not lose as much nitrogen from leaves as non-infected plants, making these plants more attractive to the aphids, increasing the chances of virus transmission to non-infected plants
  • The amount of virus in the plants was greater in eCO2 than under ambient CO2, indicating potentially greater transmission efficiency of the virus.

Next steps

Crown rot

Overall, the results suggest that crown rot severity will increase with rising CO2, reducing yields and potentially increasing the severity of more aggressive strains. Breeding programs for resistant lines will need to continue but current practices appear to be effective under future eCO2 conditions.

Further research is required to address the following questions:

  1. How will the combined effect of warming and eCO2 impact on CR pathogens and host-plant resistance
  2. How will the gradual rise in CO2 and temperature interact with drought to influence yield and quality of CR-infected crops?
  3. How will pathogens behave and evolve in farming systems under warming and eCO2 over several seasons of monoculture / rotation?

Barley yellow dwarf virus

These results may have important implications for the epidemiology of BYDV under future climates in Australia. Ongoing studies in the AGFACE and in chambers incorporate wheat cultivars with different tolerances to BYDV hosts as well as temperature interactions. Future research should also include other cereal crops and different agronomic practices to better understand the pest and disease interactions.

Related resources

Titlesort ascending Excerpt
Piotr Trebicki - BYDV and climate change: why important? (poster) Presented by Piotr Trebicki, DEPI, at the AGFACE Crop Science Workshop
Piotr Trebicki - AGFACE results: pests and diseases Presented by Piotr Trebicki, DEPI, at the AGFACE Crop Science Workshop. 
AGFACE fact sheet (2014) Fact sheet profiling the project Australian Grains Free Air Carbon dioxide Enrichment program.