Fungal Toxins in Wheat: Innovative Cropping Systems Reduce Fusarium Mycotoxins

Fungal toxins in wheat endanger the health of humans and animals. Agroscope investigated three cropping systems under reduced tillage to improve the quality and yield of wheat harvests using alternative crop protection strategies.

Fusarium head blight is a devastating fungal disease of wheat that leads to crop losses and contamination of the grains with fungal toxins (mycotoxins), such as deoxynivalenol (DON) and zearalenone (ZEN). Mycotoxins in wheat are a threat to human and animal health. In Switzerland, Fusarium head blight is mainly caused by the fungal species Fusarium graminearum. 

Crop rotation, ploughing and plant protection against fungal infection

Suitable crop rotation with non-host plant species and burying crop residues by ploughing are effective farming practices to reduce the risk of Fusarium infection. On the other hand, reduced tillage improves soil quality and is encouraged by direct payments in several cantons. Besides adjusted crop rotations and tillage, other measures to reduce fungal infection include the selection of less susceptible wheat varieties and the use of synthetic pesticides. However, the efficacy of fungicides is often insufficient due to the short period of application (anthesis) and the development of resistant fungal strains. Moreover, there is a growing tendency to reduce the reliance on synthetic plant protection products. Therefore, new strategies should be investigated to prevent Fusarium infection and contamination of harvested products with mycotoxins

Investigation of three cropping systems to reduce Fusarium mycotoxins

In the context of a maize-wheat crop rotation under reduced tillage, Agroscope investigated three innovative strategies to control Fusarium head blight and to reduce mycotoxins in wheat.

“Cut-and-carry” biofumigation: Biofumigation is a soil disinfection process based on the release of glucosinolate-breakdown products from mustard plants incorporated into the soil, which inhibits the growth of several microbial species. “Cut-and-carry” green manure is a fertilisation strategy whereby nitrogen-fixing crops, such as legumes or grass-clover mixtures, are chopped and used to fertilise a cash crop in another field. In addition to the benefits for soil fertility, this strategy could also be employed to suppress diseases where infection occurs through the soil or infected crop residues. “Cut-and-carry” biofumigation with mustard could inhibit the growth of Fusarium graminearum overwintering in crop residues, thus reducing the development of Fusarium head blight in the subsequent cereal crop.

Maize intercropping: Intercrops provide several advantages in the production system, such as nutrient capture, improved soil structure and soil organic matter, protection against erosion, weed suppression and increased belowground and aboveground biodiversity in the field. Furthermore, the total yield can be increased throughout the crop rotation. Five maize intercropping systems were investigated, including red clover, sudangrass, phacelia, white mustard and Indian mustard, and were compared with maize as a sole crop (no intercropping).

Cover cropping: Agroscope tested five treatments: Herbicide without cover crop and ploughing without cover crop were compared with white mustard, Indian mustard and winter pea cover crops.

Most important results

“Cut-and-carry” biofumigation: Compared with the control treatment (infected crop residues), the treatments with mulch layers of white mustard, Indian mustard and berseem clover reduced the DON and ZEN contents in wheat grains by 37–58% and 65–87%, respectively, while increasing the wheat yield by up to 15%.

Maize intercropping: Compared with the control (sole maize), the intercropping systems maize–white mustard and maize–Indian mustard reduced the DON content in grains of the subsequent winter wheat crop by 58% and 32%, respectively. The maize–phacelia and maize–white mustard systems reduced the ZEN content by 34% and 47%, respectively. However, the substantial reduction of mycotoxins was observed only under moderate disease pressure (year 2017) but not under very high disease pressure (year 2019). Intercropping had no negative effects on maize yield.

Cover cropping: By growing interval cover crops between silage maize and wheat, i.e. white mustard, Indian mustard or winter pea, the DON content in grains of the subsequent spring wheat crop was reduced by up to 74%. Moreover, all cover crops increased the grain yield of spring wheat by 13–25%.