Fusarium crown rot under continuous cropping of susceptible and partially resistant wheat in microcosms at elevated CO₂

Abstract

This study examines the CO 2 -mediated influence of plant resistance on crown rot dynamics under continuous cropping of partially resistant wheat line 249 and the susceptible cultivar Tamaroi. Disease incidence, severity, deoxynivalenol and Fusarium biomass were assessed after each cycle in microcosms established at ambient and 700 mg kg À1 CO 2 using soil and stubble of these wheat lines from a field experiment with free to air CO 2 enrichment. Monoconidial isolates from wheat stubble were collected initially, and after five cropping cycles, to compare the frequency and aggressiveness of Fusarium species in the two populations. Aggressiveness was measured using a high-throughput seedling bioassay. At elevated CO 2 , the higher initial incidence in Tamaroi increased with cropping cycles, but incidence in 249 remained unchanged. Incidence at ambient CO 2 did not change for either line. Elevated CO 2 induced partial resistance in Tamaroi, but not in 249. Increased Fusarium biomass in wheat tissue at elevated CO 2 matched raised deoxynivalenol of the stem base in both lines. After five cycles of continuous wheat cropping, aggressiveness increased in pathogenic F. culmorum and F. pseudograminearum by 110%, but decreased in weakly pathogenic F. equiseti and F. oxysporum by 50%. CO 2 and host resistance interactively influenced species frequency, and the highly aggressive F. pseudograminearum became dominant on Tamaroi irrespective of CO 2 concentration, while its frequency declined on 249. This study shows that induced resistance at elevated CO 2 will not reduce crown rot severity, or impede the selection and enrichment of Fusarium populations with increased aggressiveness.

Rising atmospheric CO2 concentration may imply higher risk of Fusarium mycotoxin contamination of wheat grains

“…Research on maize found that elevated CO2 level increased susceptibility to Fusarium verticillioides proliferation with no change in mycotoxin levels (Vaughan et al 2014). In wheat, an increase in Fusarium pseudograminearum biomass and/or in stem browning was found in response to elevated CO2 in some situations, depending on the varieties (Melloy et al 2010(Melloy et al , 2014. Fungal biomass increased significantly at elevated CO2 in two of the three reported studies.…”

“…Infection severity was, however, in no close relation with the grain yield (Mesterházy 1995). A study on Fusarium crown rot revealed that increased Fusarium biomass in wheat tissue at elevated CO2 matched raised DON content of the stem base under continuous cropping (Khudhair et al 2014). A clear relationship was, however, not found between disease severity in the case of natural infection and DON content as high disease pressure of Fusarium resulted in a higher DON content or no correlation depending on the year (Paterson and Lima 2010).…”

Fusarium crown rot caused by Fusarium pseudograminearum in cereal crops: recent progress and future prospects

“…Climate change can have a dramatic effect, not only on plant growth and development, but also on pathogen biology (Chakraborty et al, 2000). The effects of climate change, and in particular both elevated CO 2 and altered temperatures, on the aggressiveness of F. pseudograminearum have been investigated (Khudhair et al, 2014;Melloy et al, 2010Melloy et al, , 2014Sabburg et al, 2015). Under glasshouse conditions, elevated CO 2 increases disease incidence (measured as the proportion of infected tillers) and severity (measured as stem browning and increased fungal biomass) .…”

Development of three fusarium crown rot causal agents and systemic translocation of deoxynivalenol following stem base infection of soft wheat

“…However, FCR has been reported from all wheat cultivation areas (Chakraborty et al ., ) including Australia (Backhouse et al ., ), North America (Smiley et al ., ), Africa (Lamprecht et al ., ) and China (Li et al ., ). The disease appears to be increasingly important globally in part, at least, because resistant wheat varieties are commercially unavailable (Khudhair et al ., ). FCR is predominantly caused by Fusarium pseudograminearum (Obanor & Chakraborty, ) but also other species such as Fusarium culmorum and Fusarium graminearum may cause the disease throughout the world (Akinsanmi et al ., ; Dyer et al ., ).…”