Fungal diseases are a yield-limiting factor for wheat. Their management in organic production systems is one of the prevailing challenges because it must be based mainly on indirect measures through agricultural practices. Variety mixtures are one of these practices, a concept that has been demonstrated to improve several factors affecting yield. Recently, it has become a practice that enables sustainability in agriculture. Our research aim is to evaluate the capacity of this practice to control three fungal diseases (foliar and ear) on durum wheat. This study was conducted over two consecutive years (2019 and 2020) at two locations: a certified organic farm in the Benslimane region (2019) and the National School of Agriculture farm in Meknes (2020). Four durum wheat varieties (Isly, Tarek, Karim, and Nassira) were used to create the mixture. The parameters that were monitored were the disease severity, the grain yield, and its components. The analysis of variance for the three fungal diseases’ severity was significant. The variety that showed resistance to all diseases was the Isly variety, and the most susceptible variety was the Nassira variety. The resistance of the other varieties to the diseases was variable from one year to the other. The mixture showed average severity values. It allowed a reduction in the severity of leaf rust of 47% during the first year and 30% during the second year compared to the most susceptible variety (Nassira). In the case of HLB (helminthosporiosis leaf blight), it reduced the disease by 47% during the first year and 34% during the 2020 season. For ear disease, Fusarium head blight (FHB), the reduction was 68% during the year 2019 and 49% during 2020. The mixture also ensured yield stability between the two trial years (1.66 t ha⁻¹ and 1.54 t ha⁻¹).

In the organic production system, the management of diseases and pests is based on agricultural practices rather than the use of certified phytosanitary inputs. The mixture of varieties is an agricultural practice that has shown its interest not only in the management of diseases and pests but also in the increase and stability of crop yields. The objective of our study is to evaluate the performance of this practice in the management of fusarium head blight in wheat. To achieve this objective, we conducted four trials. Two trials (one on durum and the other on soft wheat) in 2019 on a certified organic farm and the two trials were repeated in 2020. During the two years of experimentation, we compared the mixture of four durum wheat varieties and the mixture of four soft wheat varieties with the monoculture varieties. In the field, we evaluated the severity of Fusarium head blight and wheat yield components as well as the grain yield. The results showed a significant difference between the different treatments for Fusarium head blight severity and yield components for both species and in both years of the experiment.