Changeable watering conditions nonspecifically affect quantitative traits in Fusarium head blight-wheat/barley pathosystem

From an economic and toxicological point of view, Fusarium head blight (FHB), a biotic stress, is one of the most dangerous diseases of wheat and barley worldwide. It is recently known that humidity, an abiotic stress, enhances susceptibility of cereal heads to FHB infection and aggressiveness of Fusarium pathogens; however, whether its effect on pathogenicity in fungi and resistance in hosts is specifically or not is unknown. To end this, pot bio-experiments under natural climatic conditions during the growing season 2022/2023 were conducted to determine the nature of post-anthesis moisture influence on quantitative traits in FHB-wheat/barley interaction. Five durations of spray-irrigation of 0, 7, 14, 21, and 28 days, eight bread wheat, durum wheat and barley cultivars with different levels of FHB and 16 Fusarium isolates of various aggressiveness belonging to four FHB pathogens were involved under split-split-plot design. Evaluation of FHB quantitative traits to the variable watered conditions was through the quantification of Fusarium incidence, DI, Fusarium severity, DS, 21 days after inoculation as well as Fusarium-damaged kernel (FDK) percentages on harvested grain. Changeable watered conditions applied on plant materials of different resistance levels nonspecifically affected aggressiveness, DI, DS and FDK, of the tested Fusarium isolates whatever their pathogenic backgrounds (low, medium and high aggressiveness) and genetic origin (i.e., F. culmorum, F. solani, F. verticillioides, and F. equiseti). The four susceptible responses, i.e., susceptible, susceptible to moderately susceptible, moderately susceptible and moderately resistant, did not vary also in their relative rankings in the eight tested cereal plants. From a grower’s perspective, prolonged rainy periods following wheat and barley flowering should be a signal to scout wheat and barely crops for FHB symptoms and mycotoxin accumulation, even if pre-flowering conditions were not conducive to FHB. This indicates for the first time that post-anthesis moisture nonspecifically affect development of Fusarium isolates in tissues of wheat and barley heads. Our results have obvious implications for disease epidemiology in complex relationship moisture, resistances of cultivars, and aggressiveness of Fusarium pathogens.