Photosynthetic Efficiency in Flag Leaves and Ears of Winter Wheat during Fusarium Head Blight Infection

Fusarium head blight (FHB) is one of the most serious fungal diseases of wheat (Triticum aestivum L.). It causes major reduction of grain yield and quality, while the safety of wheat products is at risk due to mycotoxin contaminations. To contribute to a better understanding of mechanisms governing more efficient defense strategies against FHB, an evaluation of photosynthetic efficiency was performed during different phases of infection, i.e., before visual symptoms occur, at the onset and after the development of disease symptoms. Six different winter wheat varieties were artificially inoculated with the most significant causal agents of FHB (Fusarium graminearum and F. culmorum) at two different locations. Photosynthetic efficiency was assessed in flag leaves and ears of inoculated and untreated (control) plants based on measurements of chlorophyll a fluorescence rise kinetics and the calculation of JIP-test parameters. Obtained results indicate that the response of wheat to Fusarium infection includes changes in photosynthetic efficiency which can encompass alternating reductions and increases in photosynthetic performance during the course of the infection in both flag leaves and ears. FHB-induced photosynthetic adjustments were shown to be somewhat variety-specific, but location was shown to be a more significant factor in modulating the response of wheat to Fusarium infection. Changes in chlorophyll a fluorescence rise kinetics could be detected prior to visible symptoms of the disease. Therefore, this method could be applied for the early detection of Fusarium infection, particularly the analysis of L-band appearance, which showed a similar response in all inoculated plants, regardless of variety or location.