The effect of CO2 and temperature on Fusarium crown rot incidence, severity, pathogen colonisation, toxigenic potential and host resistance in a selection of wheat germplasm

Melloy, Paul (2015). The effect of CO2 and temperature on Fusarium crown rot incidence, severity, pathogen colonisation, toxigenic potential and host resistance in a selection of wheat germplasm PhD Thesis, School of Agriculture and Food Sciences, The University of Queensland. doi:10.14264/uql.2016.1

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Author Melloy, Paul
Thesis Title The effect of CO2 and temperature on Fusarium crown rot incidence, severity, pathogen colonisation, toxigenic potential and host resistance in a selection of wheat germplasm
Formatted title
The effect of CO2 and temperature on Fusarium crown rot incidence, severity, pathogen colonisation, toxigenic potential and host resistance in a selection of wheat germplasm
School, Centre or Institute School of Agriculture and Food Sciences
Institution The University of Queensland
DOI 10.14264/uql.2016.1
Publication date 2015-12-18
Thesis type PhD Thesis
Supervisor Friday Obanor
Elizabeth Aitken
Jo Luck
Total pages 149
Total colour pages 17
Total black and white pages 132
Language eng
Subjects 0607 Plant Biology
0703 Crop and Pasture Production
0699 Other Biological Sciences
Formatted abstract
Rising atmospheric CO2 may impact on host and pathogen interactions to the benefit or detriment of crop productivity. The wheat disease Fusarium crown rot (FCR), caused by the pathogen Fusarium pseudograminearum, is predicted to increase in incidence with rising CO2 due to changes in wheat resistance. Fusarium spp. regularly reduce the quantity and quality of wheat yields around the globe. Reported here are a collection of studies which show FCR incidence and susceptibility in wheat plants is likely to increase in a future with higher atmospheric [CO2] and warmer temperatures. FCR incidence was significantly influenced by e[CO2] in all three experiments. FCR incidence was higher in elevated CO2 (e[CO2]) treatments within the glasshouse. Warmer temperatures in combination with e[CO2] caused an increased FCR incidence earlier in the host growth stages. FCR incidence was also higher on mature plants grown in e[CO2] treatments of the warmer 2011 season field study at the Australian Grains Free-Air Carbon-dioxide Enrichment (AGFACE) facility. The cooler and wetter season, 2010, showed lower FCR incidence on mature plants in the e[CO2] treatments compared to ambient (a[CO2]). These changes in FCR incidence under e[CO2], in the glasshouse and AGFACE, were dependent on host genotype. Indicating FCR incidence mitigation in future e[CO2] climates might be possible through genotype selection and breeding programs. Higher FCR susceptibility under e[CO2] may have contributed to the observed increase in FCR incidence. Plants grown under e[CO2] at both sampling stages in the 2011 AGFACE season and soft dough of the 2010 season showed an increased FCR susceptibility. White-head incidence, a FCR symptom, was also shown to increase under elevated [CO2] in the continuous cropping experiment which was undertaken in a controlled environment facility (CEF).

FCR severity may also increase in future climates with e[CO2]. Elevated [CO2] was shown to increase FCR severity in both warm and cool temperature glasshouse environments, compared to a[CO2] with cool temperatures. In the e[CO2] treatment with cool temperatures FCR severity increased at a faster rate between sampling stages: node development, anthesis, soft dough and crop maturity. In the field FCR severity only significantly increased in e[CO2] treatments when compared to the changes in relative Fusarium biomass, which was described as an increase in FCR susceptibility or lower FCR resistance.

Cropping areas practicing minimum till will be more likely to accumulate FCR inoculum under e[CO2] through a greater quantity of infected crop debris at the end of a cropping season. Relative Fusarium biomass increased faster between sampling stages in the e[CO2] with cool temperature glasshouse environments and showed greater colonisation compared to the other environments at soft dough and crop maturity. Temperature induced FCR resistance may have been the reason for stalled relative Fusarium biomass increases between anthesis and soft dough sampling stages in the e[CO2] warm temperature glasshouse environment. Despite this relative Fusarium biomass was still greater on mature plants in e[CO2] with warm temperatures compared with the a[CO2] with cool temperature environment. Increased relative Fusarium biomass under e[CO2] treatments in the glasshouse was dependent on the growing temperature and sampling stage. Stubble management to reduce FCR inoculum will remain important between seasons. Zero till farming under e[CO2] will be likely to lead to an increased incidence of white heads over successive cropping cycles for susceptible wheat cultivars as seen with Tamaroi in the CEF. Partially resistant genotype 2-49, however did not show the same increased white head incidence. Continuous cropping increased pathogen aggressiveness and species diversity by favouring highly pathogenic Fusarium species F. pseudograminearum and F. culmorum after five continuous cropping cycles, regardless of CO2 treatment.

The trichothecene mycotoxin deoxynivalenol (DON) was found to increase in FCR infected plants grown under e[CO2]. DON contaminated straw will likely become more problematic in the future if warmer growing temperatures with rising [CO2] promote DON production, as was shown in the warmer 2011 AGFACE season. Fusarium toxigenic potential in the stem (DON normalised to the quantity of relative Fusarium biomass) was higher at crop maturity in the e[CO2] treatments of the 2011 AGFACE season as well as the CEF continuous cropping experiment. In the 2010 season however, toxigenic potential was lower under e[CO2]. Grain samples from e[CO2] treatments in the CEF showed lower DON concentrations compared to a[CO2]. Limiting DON contamination in the stem might be possible through choice of cultivar; toxigenic potential was dependent on genotype, as well as sampling stage and season. Seasonal and e[CO2] effects on mycotoxins need further study. The experiments reported here regularly showed an e[CO2] and seasonal, or temperature, interactive effect on crown rot development and DON toxigenic potential.

FCR resistance, susceptibility and crown rot induced crop losses through lower grain weight, were dependent on host genotype. On average genotype L2-120, 2-49, and Sunco showed the highest resistance to FCR while Tamaroi, Janz and Wyalkatchem showed the lowest resistance. Overall, increasing atmospheric [CO2] is likely to lead to a greater build-up of FCR inoculum in wheat, encouraging an increased disease incidence in susceptible varieties of wheat. With greater FCR incidence and subsequent changes to toxin production is likely to boost DON in plant stems. From this research it is likely that e[CO2] will lower crop productivity where FCR is present and negatively impact on the quantity and quality of future crop yields. The consequences of these changes may be mitigated through crop breeding programs with the purpose of developing wheat varieties with improved FCR resistance, FCR tolerance and the ability to detoxify DON mycotoxin.
Keyword Climate change
Fusarium pseudograminearum
Host and pathogen interactions

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Created: Mon, 30 Nov 2015, 14:44:14 EST by Paul Melloy on behalf of University of Queensland Graduate School