Rain Splash Dispersal of Gibberella zeae Within Wheat Canopies in Ohio

Abstract

Rain splash dispersal of Gibberella zeae, causal agent of Fusarium head blight of wheat, was investigated in field studies in Ohio between 2001 and 2003. Samplers placed at 0, 30, and 100 cm above the soil surface were used to collect rain splash in wheat fields with maize residue on the surface and fields with G. zeae-infested maize kernels. Rain splash was collected during separate rain episodes throughout the wheat-growing seasons. Aliquots of splashed rain were transferred to petri dishes containing Komada's selective medium, and G. zeae was identified based on colony and spore morphology. Dispersed spores were measured in CFU/ml. Intensity of splashed rain was highest at 100 cm and ranged from 0.2 to 10.2 mm h(-1), depending on incident rain intensity and sampler height. Spores were recovered from splash samples at all heights in both locations for all sampled rain events. Both macroconidia and ascospores were found based on microscopic examination of random samples of splashed rain. Spore density and spore flux density per rain episode ranged from 0.4 to 40.9 CFU cm(-2) and 0.4 to 84.8 CFU cm(-2) h(-1), respectively. Spore flux density was higher in fields with G. zeae-infested maize kernels than in fields with maize debris, and generally was higher at 0 and 30 cm than at 100 cm at both locations. However, on average, spore flux density was only 30% lower at 100 cm (height of wheat spikes) than at the other heights. The log of spore flux density was linearly related to the log of splashed rain intensity and the log of incident rain intensity. The regression slopes were not significantly affected by year, location, height, and their interactions, but the intercepts were significantly affected by both sampler height and location. Thus, our results show that spores of G. zeae were consistently splash dispersed to spike heights within wheat canopies, and splashed rain intensity and spore flux density could be predicted based on incident rain intensity in order to estimate inoculum dispersal within the wheat canopy.

DON content in oat grains in Norway related to weather conditions at different growth stages

“…Crop debris is recognized as a source of F. graminearum inoculum (Pereyra et al 2004). Rainfall is important for conidial dispersal (Xu 2003;Paul et al 2004), thus the positive impact of mean daily precipitation found in our study confirms the importance of spread of the splash dispersed macroconidia (Paul et al 2004;Skelsey and Newton 2015) when the plant is most susceptible to infection (Tekle et al 2012). Rain increases the moisture of crop debris (Manstretta and Rossi 2015) and thus also favours the development of perithecia and maturation of ascospores (Manstretta and Rossi 2016).…”

Predicting Fusarium Head Blight Epidemics With Weather-Driven Pre- and Post-Anthesis Logistic Regression Models

“…One shortcoming with feature selection is the candidate set itself: selection algorithms will generally select something from the candidate set and, if the latter happened to be relatively small and possibly weighted with r-derived predictors (e.g., more r-based predictors than rh-based predictors in the data matrix), one would expect r showing up in at least some of the models returned by the selection algorithm. Rainfall is certainly important for conidial dispersal (48,50) but other effects of r may be more related to the creation of wet surfaces or to increases in atmospheric moisture. With the (sometimes large) correlations between weather variables, we believe that r is probably a surrogate for other moisture-related variables that are more directly related to components of the FHB cycle.…”

Rainfall drives atmospheric ice-nucleating particles in the coastal climate of southern Norway

“…Both correlations are statistically significant (p < 0.01). There are at least two reasons for the deviations: first, depending on rain intensity and raindrop size, the same amount of weekly rainfall can have a very different impact on aerosolising microorganisms from vegetation (Paul et al, 2004). Second, the presence and density of IN-active (ice nucleation active) material on surfaces hit by raindrops may change with season or on shorter timescales.…”