Effects of Climate and Cropping Systems on Perithecial Production by Fusarium asiaticum and F. graminearum sensu stricto.

The two dominant Fusarium head blight (FHB) pathogens in China (3-acetyl-deoxynivalenol chemotype of Fusarium asiaticum [F. asiaticum 3ADON] and 15-acetyl-deoxynivalenol chemotype of F. graminearum sensu stricto [F. graminearum 15ADON]) display distinct geographic distributions with different cropping systems. The effects of climate and cropping systems on perithecial production by these two pathogens were examined at four sites annually over three years (five locations in total). Within each year, perithecial production by F. asiaticum 3ADON and F. graminearum 15ADON on inoculated stalks (rice and maize in 2017; maize only in 2020 and 2023) decreased from south (Yancheng in 2017; Xinyang in 2020 and 2023) to north (Zhumadian, Xuchang, and Xinxiang in all three years), with significant differences among sites (P < 0.01). Production on maize stalks was higher than on rice stalks at the same site in 2017, the only year when both stalk types were evaluated. On maize stalks, no significant differences were observed in 2017 or 2023 (P > 0.05), whereas in 2020 production was markedly lower, and differed significantly between species (P < 0.01). Correlation and stepwise regression analyses identified average daily temperature from stalk placement to investigation (TEM) and average daily relative humidity in mid-March (RH3m) as the key factors affecting perithecial production on inoculated maize stalks. Pathogen composition on naturally diseased wheat spikes and crop residues revealed that F. asiaticum 3ADON dominated (≥83.3%) in wheat-rice rotation fields south of the Huai River, whereas F. graminearum 15ADON was prevalent (≥71.4%) in wheat-maize rotation fields north of the Huai River. Inoculated stalks displayed no consistent differences in perithecial production between the two species. This is inconsistent with their natural distribution patterns. Therefore, under equivalent initial colonization levels, temperature, relative humidity, and precipitation from mid-January (stalk placement) to mid-April (wheat flowering) do not drive the geographic distributions of F. asiaticum 3ADON and F. graminearum 15ADON by influencing perithecial production on crop residues.