Fusarium pseudograminearum and F. culmorum affect the root system architecture of bread wheat

Yield losses of bread wheat due to crown rot can be more severe when drought conditions occur during the grain-filling period. Root architecture characteristics are important for soil exploration and belowground resource acquisition and are essential for adaptation to water-limited environments. Traits such as root angle, length and density have been strongly associated with acquisition efficiency and contribute to yield stability of the crop. The impact of crown rot pathogens on wheat root architecture is poorly understood. We examined differences in root angle, length and number, as well as dry root weight of the crown rot-susceptible bread wheat cultivar, Livingston inoculated with one of two crown rot pathogens Fusarium culmorum or Fusarium pseudograminearum in a transparent-sided root observation chamber. Significant adverse impacts on plant health and growth were revealed by visual discolouration of the leaf sheaths; fresh and dry shoot weight; leaf area of the oldest and the youngest fully expanded leaf and leaf number. Values of most recorded root system measurements were reduced when inoculated with either F. culmorum or F. pseudograminearum. In contrast, root angle was increased in the presence of F.culmorum but was not significantly changed by F. pseudograminearum. The development of whiteheads and grain losses in bread wheat caused by crown rot have previously been associated with blockages of the vascular systems. The method employed here was able to identify differences in the pathogen impacts on roots, which were not detected using previous systems. This research indicates that in the presence of F. culmorum and F. pseudograminearum infection, not only reductions in the size and biomass of the shoot system but also changes in the length, biomass and architecture of the root system could play an important role in yield loss.