Abstract
Wheat is one of the world’s most economically important cereal crop, grown on 220 million hectares. Fusarium head blight (FHB) disease is considered a major threat to durum (Triticum turgidum subsp. durum (Desfontaines) Husnache) and bread wheat (T. aestivum L.) cultivars and is mainly managed by the application of fungicides at anthesis. However, fungicides are applied when FHB symptoms are clearly visible and the spikes are almost entirely bleached (% of diseased spikelets > 80%), by when it is too late to control FHB disease. For this reason, farmers often react by performing repeated fungicide treatments that, however, due to the advanced state of the infection, cause a waste of money and pose significant risks to the environment and non-target organisms. In the present study, we used unmanned aerial vehicle (UAV)-based thermal infrared (TIR) and red-green-blue (RGB) imaging for FHB detection in T. turgidum (cv. Marco Aurelio) under natural field conditions. TIR and RGB data coupled with ground-based measurements such as spike’s temperature, photosynthetic efficiency and molecular identification of FHB pathogens, detected FHB at anthesis half-way (Zadoks stage 65, ZS 65), when the percentage (%) of diseased spikelets ranged between 20% and 60%. Moreover, in greenhouse experiments the transcripts of the key genes involved in stomatal closure were mostly up-regulated in F. graminearum-inoculated plants, demonstrating that the physiological mechanism behind the spike’s temperature increase and photosynthetic efficiency decrease could be attributed to the closure of the guard cells in response to F. graminearum. In addition, preliminary analysis revealed that there is differential regulation of genes between drought-stressed and F. graminearum-inoculated plants, suggesting that there might be a possibility to discriminate between water stress and FHB infection. This study shows the potential of UAV-based TIR and RGB imaging for field phenotyping of wheat and other cereal crop species in response to environmental stresses. This is anticipated to have enormous promise for the detection of FHB disease and tremendous implications for optimizing the application of fungicides, since global food crop demand is to be met with minimal environmental impacts.
Highlights
Wheat is one of the most cultivated crops worldwide, grown on 220 million hectares and its annual production is estimated to account for more than 700 million tons, providing more than 20% of total human food calories (Khan et al, 2020; Ma et al, 2020)
To maximize Fusarium head blight (FHB) disease control efficiency, we explored the use of UAVbased RGB and thermal infrared (TIR) imaging supported by ground-truthing to detect the presence of FHB in T. turgidum
The present study revealed that: (i) stomatal closure is the physiological mechanism responsible for temperature increase and photosynthetic efficiency decrease in T. turgidum spikes during FHB infection; (ii) vegetation indices (VIs) and temperatures extracted from RGB and TIR imaging data can detect these physiological changes; and (iii) different transcriptional regulations exist between drought-stressed and F. graminearum-inoculated plants
Summary
Wheat is one of the most cultivated crops worldwide, grown on 220 million hectares and its annual production is estimated to account for more than 700 million tons, providing more than 20% of total human food calories (Khan et al, 2020; Ma et al, 2020). Among the plant fungal diseases, Fusarium head blight (FHB) is one of the most destructive diseases leading to 10–70% of yield loss during the epidemic years (McMullen et al, 2012). FHB is caused by the Fusarium graminearum species complex (FGSC), which embraces 16 different species. It is considered the most devastating wheat disease due to the lack of resistant cultivars, the significant yield loss and grain quality reduction, and the health risks associated with the contamination of crops with mycotoxin such as deoxynivalenol (DON) and zearalenone (ZEA), produced during the infection progress (Yang et al, 2013; Dweba et al, 2017). Given the current global warming associated with increased temperatures, major epidemics of FHB are occurring. Proper cultivation schemes and field management are essential to alleviate its threat (Bai and Shaner, 2004; Vaughan et al, 2016; Ma et al, 2020; Rod et al, 2020)
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