The Distribution of <i>Fusarium graminearum</i> and <i>Fusarium asiaticum</i> Causing Fusarium Head Blight of Wheat in Relation to Climate and Cropping System

Abstract

In the main wheat production area of China (the Huang Huai Plain [HHP]), both <i>Fusarium graminearum</i> and <i>Fusarium asiaticum</i>, the causal agents of Fusarium head blight (FHB), are present. We investigated whether the relative prevalence of <i>F</i>. <i>graminearum</i> and <i>F</i>. <i>asiaticum</i> is related to cropping systems and/or climate factors. A total of 1,844 <i>Fusarium</i> isolates were obtained from 103 fields of two cropping systems: maize-wheat and rice-wheat rotations. To maximize the differences in climatic conditions, isolates were sampled from the north and south HHP regions. Based on the phylogenetic analysis of <i>EF</i>-<i>1</i>α and <i>Tri101</i> sequences, 1,207 of the 1,844 isolates belonged to <i>F</i>. <i>graminearum</i>, and the remaining 637 isolates belonged to <i>F</i>. <i>asiaticum</i>. The former was predominant in the northern region: 1,022 of the 1,078 <i>Fusarium</i> isolates in the north were <i>F</i>. <i>graminearum</i>. The latter was predominant in the southern region: 581 of the 766 <i>Fusarium</i> isolates belonged to <i>F</i>. <i>asiaticum</i>. Using an analysis based on generalized linear modeling, the relative prevalence of the two species was associated more with climatic conditions than with the cropping system. <i>F</i>. <i>graminearum</i> was associated with drier conditions and cooler conditions during the winter but also with warmer conditions in the infection and grain-colonization period as well as with maize-wheat rotation. The opposite was true for <i>F</i>. <i>asiaticum</i>. Except for the 15-acetyldeoxynvalenol genotype, the trichothecene chemotype composition of <i>F</i>. <i>asiaticum</i> differed between the two cropping systems. The 3-acetyldeoxynivalenol genotype was more prevalent in the maize-wheat rotation, whereas the nivalenol genotype was more prevalent in the rice-wheat rotation. The results also suggested that environmental conditions in the overwintering period appeared to be more important than those in the infection, grain-colonization, and preanthesis sporulation periods in affecting the relative prevalence of <i>F</i>. <i>graminearum</i> and <i>F</i>. <i>asiaticum</i>. More research is needed to study the effect of overwintering conditions on subsequent epidemic in the following spring.