Disease responses of hexaploid spring wheat (Triticum aestivum) culms exhibiting premature senescence (dead heads) associated with Fusarium pseudograminearum crown rot

Abstract

Hexaploid spring wheat (Triticum aestivum) may exhibit significant crown rot disease responses to infection by Fusarium pseudograminearum, with a range of susceptibility levels available in commercial cultivars. Dry conditions during grain-fill may lead to the expression of prematurely senescing culms, which typically fail to set grain. Assessment of hexaploid spring wheat plants exhibiting both non-senescent and prematurely senescent culms was performed using visual discolouration, Fusarium pseudograminearum biomass, vascular colonisation and quantification of wheat DNA in culm sections sampled at three different heights above the crown and at the peduncle.A comparison of these parameters at four time points from milk development, when senescent culms are first observed, to maturity was conducted. Samples from six commercial cultivars were collected in 2014 from Narrabri and Tamworth, New South Wales and Wellcamp, Queensland. Prematurely senescent culms exhibited greater visual discolouration, Fusarium pseudograminearum biomass and vascular colonisation than non-senescent culms in each cultivar. Colonisation of xylem and phloem tissue was extensive in the basal portions of prematurely senescent culms (36 to 99%), and suggests significant impacts on water and nutrient movement during crown rot disease. Maturation coincided with significant changes in Fusarium pseudograminearum biomass and vascular colonisation. Wheat DNA content varied among cultivars, culm conditions, culm sections and sampling times. The variation in the severity of disease states between culms of the same plant suggests that the timing of initiation of infection in individual culms may vary..

Using Yield Response Curves to Measure Variation in the Tolerance and Resistance of Wheat Cultivars to Fusarium Crown Rot

“…2). This result is consistent with the widely reported lack of resistance that durum wheat exhibits to crown rot, when compared with bread wheat (Hollaway et al 2013;Knight and Sutherland 2015;Knight et al 2017;Martin et al 2013).…”

“…These prematurely senesced spikes contain either no grain or shriveled grain, depending on the timing of stress relative to grain development. A recent study has demonstrated that tillers displaying greater severity of stem browning and F. pseudograminearum biomass more typically exhibit whiteheads (Knight et al 2017).…”

The Promise of Hyperspectral Imaging for the Early Detection of Crown Rot in Wheat

“…Crown rot is a significant stubble-soil fungal disease that affects the cereal industry worldwide as it has been reported in the U.S., China's southeast coast region, Africa, central Europe, and Australasia [1][2][3][4]. Fusarium pseudograminearum is the major contributing pathogen causing crown rot that is commonly found in Australian wheat [5]. Although wheat can be influenced by other fungal diseases, F. pseudograminearum has been identified and detected in 48% of fungal disease isolates from wheat in Australia [1].…”

“…For example, if wheat, at the milk stage, experiences reduced rainfall, the probability of whitehead appearance in the disease-infected wheat crops will greatly increase [21,22]. The pathogen colonizes and damages the plants' vascular system, which is responsible for water and nutrient uptakes in the plant [5], and water stress during or shortly after the wheat flowering period will increase the symptoms of the disease [23]. Once wheat is infected with crown rot, the accumulation of a high level of the mycotoxin deoxynivalenol (DON) will make the grains inedible [24,25].…”

Stubble trouble! Moisture, pathogen fitness and cereal type drive colonisation of cereal stubble by three fungal pathogens

“…Saprotrophic growth of fungal pathogens is likley to depend on moisture, stubble characteristics and the individual different species requirements, plus additional factors like temperature and competition between microbes (Pfender et al 1988). In susceptible crops, significant mycelial growth may have already occurred prior to senescence (Knight et al 2021Petronaitis et al 2020), so the infection status of a crop at maturity should also be considered. Linking the pathogenic (in-crop) colonisation with saprotrophic (postharvest) colonisation of cereal stubble is therefore needed under field conditions to fully illustrate the effect of host susceptibility on pathogen inoculum dynamics within and between seasons.…”