Effect of wheat spike infection timing on fusarium head blight development and mycotoxin accumulation

Abstract

Fusarium head blight in wheat spikes is associated with production of mycotoxins by the fungi. Although flowering is recognized as the most favourable host stage for infection, a better understanding of infection timing on disease development and toxin accumulation is needed. This study monitored the development of eight characterized isolates of F. graminearum, F. culmorum and F. poae in a greenhouse experiment. The fungi were inoculated on winter wheat spikes before or at anther extrusion, or at 8, 18 and 28 days later. Disease levels were estimated by the AUDPC and thousand-kernel weight (TKW). The fungal biomass (estimated by qPCR) and toxin concentration (deoxynivalenol and nivalenol, estimated by UPLC-UV-MS/MS) were measured in each inoculated spike, providing a robust estimation of these variables and allowing correlations based on single-individual measurements to be established. The toxin content correlated well with fungal biomass in kernels, independently of inoculation date. The AUDPC was correlated with fungal DNA, but not for early and late infection dates. The highest disease and toxin levels were for inoculations around anthesis, but early or late infections led to detectable levels of fungus and toxin for the most aggressive isolates. Fungal development appeared higher in kernels than in the chaff for inoculations at anthesis, but the opposite was found for later inoculations. These results show that anthesis is the most susceptible stage for FHB, but also clearly shows that early and late infections can produce significant disease development and toxin accumulation with symptoms difficult to estimate visually.

Mutual Exclusion between Fungal Species of the Fusarium Head Blight Complex in a Wheat Spike

“…A general trend in these studies is that the most competitive species does not colonize the host in coinoculations significantly more extensively than when inoculated alone (i.e., no advantage is provided by the presence of the other species), but the species with the selective disadvantage develops less extensively in the presence of a competitor than when infecting alone (2). This was once again observed by Siou et al (10,11). Such competitive interactions seem to occur at the intraspecific level as well.…”

“…Five microliters of the spore suspension was deposited inside each inoculated floret with a micropipette. After inoculation, the spikes were enclosed in a sealed transparent polyethylene bag for 3 days to maintain 100% relative humidity and to promote infection (11,21).…”

Interactions between Head Blight Pathogens: Consequences for Disease Development and Toxin Production in Wheat Spikes

“…A homogenized flour sample of around 1 g was used for toxin extraction. The UPLC-UV-MS/MS analysis of the toxin extract was performed with an Acquity Ultra-Performance liquid chromatograph coupled with a TQD tandem mass spectrometer (Waters Corp.), as described by Siou et al (10). The mass spectrometer was operated in electrospray ionization (ESI negative-ion mode) under multiple-reaction monitoring mode.…”

“…The methods for species-specific quantification of fungal DNA (extraction and qPCR) and toxin quantification (extraction and ultraperformance liquid chromatography-UV detection-tandem mass spectrometry [UPLC-UV-MS/MS] analysis) from all the tissue samples were developed in a previous study (10). The total DNA was extracted from around 50 mg of ground material using the DNeasy plant minikit (Qiagen).…”

Visual assessment and computer–assisted image analysis of Fusarium head blight in the field to predict mycotoxin accumulation in wheat grains

“…No-tillage or reduced tillage practices increase the risk of disease development and DON accumulation as compared to inversion tillage (Dill-Macky and Jones 2000). Weather conditions, among which long periods of warm temperatures and high moisture during wheat flowering, increase FHB severity (Siou et al 2014). Wheat is the most cultivated crop in France (around 5.5 million ha in 2015) as well as the most traded one (19.4 million tons exported during the 2014-15 campaign; Passion Céréales 2016).…”