Host and Cropping System Shape the Fusarium Population: 3ADON-Producers Are Ubiquitous in Wheat Whereas NIV-Producers Are More Prevalent in Rice

Abstract

In recent years, Fusarium head blight (FHB) outbreaks have occurred much more frequently in China. The reduction of burning of the preceding crop residues is suggested to contribute to more severe epidemics as it may increase the initial inoculum. In this study, a large number of Fusarium isolates was collected from blighted wheat spikes as well as from rice stubble with perithecia originating from nine sampling sites in five provinces in Southern China. Fusarium asiaticum dominated both wheat and rice populations, although rice populations showed a higher species diversity. Chemotype analysis showed that rice is the preferred niche for NIV mycotoxin producers that were shown to be less virulent on wheat. In contrast, 3ADON producers are more prevalent on wheat and in wheat producing areas. The 3ADON producers were shown to be more virulent on wheat, revealing the selection pressure of wheat on 3ADON producers. For the first time, members of the Incarnatum-clade of Fusarium Incarnatum-Equiseti Species Complex (FIESC) were found to reproduce sexually on rice stubble. The pathogenicity of FIESC isolates on wheat proved very low and this may cause the apparent absence of this species in the main wheat producing provinces. This is the first report of the Fusarium population structure including rice stubble as well as a direct comparison with the population on wheat heads in the same fields. Our results confirm that the perithecia on rice stubble are the primary inoculum of FHB on wheat and that cropping systems affect the local Fusarium population.

Gramineous weeds near paddy fields are alternative hosts for the Fusarium graminearum species complex that causes fusarium head blight in rice

“…Types of crops in crop rotation directly or indirectly promote the infection of cereal crops by Fusarium as the Fusarium ‐contaminated debris from the earlier crop can act as a reservoir for subsequent infection. Previous studies associated with FHB in China have shown that the 15ADON chemotype of F. graminearum was dominant in the northeast and Huanghuaihai regions for wheat–maize rotation, the F. asiaticum ‐3ADON was predominant in the Yangtze River region for wheat–rice rotation, and the NIV chemotype of F. asiaticum was the major chemotype in the southwest region for wheat–rice and rice–ratoon rice rotations (Zhang et al , ; Zhang et al , ; Qiu and Shi, ; Dong et al , ; Hao et al , ; Yang et al , ). F. asiaticum with the 3ADON chemotype was the dominant species in wheat, paddy, and weed samples in Jiangsu Province, but the frequencies of NIV producers in weed and paddy samples were approximately three times higher than in wheat in Jiangsu Province (Zhang et al , ; Qiu and Shi, ; Dong et al , ; Yang et al , ).…”

“…Fusarium graminearum species complex isolates vary in their ability to cause disease in different hosts (Goswami and Kistler, ). In general, both 3ADON and 15ADON chemotypes of F. graminearum and F. asiaticum are more aggressive than NIV chemotypes of F. asiaticum , F. meridionale , and F. cortaderiae in wheat (Starkey et al , ; Spolti et al , ; Umpiérrez‐Failache et al , ; Liu et al , ; Nicolli et al , ; Yang et al , ; Amarasinghe et al , ). However, there have been few reports on the pathogenicity of FGSC isolates in rice (Goswami and Kistler, ; Lee et al , ; Gomes et al , ).…”

“…Gramineous weeds in the proximity of paddy fields are likely to play an important role in FHB epidemiology. Another question raised during this study is whether weeds in the proximity of wheat fields influence FHB epidemics in Jiangsu Province, a traditional FHB–epidemic area with wheat–rice rotation in China (Yang et al , ). Further studies are necessary to investigate the significance and role of weeds in FHB epidemiology of other cereal crops in China.…”

“…In China, FHB epidemics have become more severe and more widespread over the past decade. The wheat‐growing regions, including the middle and lower reaches of the Yangtze River, have been affected by FHB, resulting in yield losses and contamination by Fusarium mycotoxins (Zhang et al , ; Zhang et al , ; Yang et al , ; Qiu et al , ). The major species of FGSC that cause FHB in cereals are F. asiaticum and F. graminearum , depending on the climate conditions and the different crop rotation systems in different regions (Qu et al , ; Yang et al , ; Zhang et al , ; Zhang et al , ; Hao et al , ; Yang et al , ; Qiu et al , ).…”

Asymptomatic weeds are frequently colonised by pathogenic species of Fusarium in cereal‐based crop rotations

“…Primary inoculum for host infection is produced on the surface of residues, such as maize stalks, wheat straw and weeds (Pereyra & Dill‐Macky, ). Therefore, anthropogenic activities (crop rotation, tillage and weed management) are key risk factors for Fusarium ‐caused diseases (Leplat et al ., ), where host plant and cropping systems may drive Fusarium population abundance (Leplat et al ., ; Yang et al ., ) and subsequent impact of associated disease.…”