Mixtures of cultivars with contrasting levels of resistance can suppress infectious diseases in wheat, as demonstrated in numerous field experiments. Most studies focused on airborne pathogens in bread wheat, while splash-dispersed pathogens have received less attention, and no studies have been conducted in durum wheat. We conducted a two-year field experiment in Tunisia, to evaluate the performance of cultivar mixtures with varying proportions of resistance (0–100%) in controlling the polycyclic, splash-dispersed disease Septoria tritici blotch (STB) in durum wheat. To measure STB severity, we used a high-throughput method based on digital image analysis of 3074 infected leaves collected from 42 and 40 experimental plots during the first and second years, respectively. This allowed us to quantify pathogen reproduction on wheat leaves and to acquire a large dataset that exceeds previous studies with respect to accuracy and precision. Our analyses show that introducing only 25% of a disease-resistant cultivar into a pure stand of a susceptible cultivar provides a substantial reduction of almost 50% in disease severity compared to the susceptible pure stand. However, comprising the resistant component of two cultivars instead of one did not further improve disease control, contrary to predictions of epidemiological theory. Susceptible cultivars can be agronomically superior to resistant cultivars or be better accepted by growers for other reasons. Hence, if mixtures with only a moderate proportion of the resistant cultivar provide a similar degree of disease control as resistant pure stands, as our analysis indicates, such mixtures are more likely to be accepted by growers.

The data is collected with automated image analysis of pictures of infected leaves. The leaves were collected from experimental plots where we tested efficacy of cultivar mixtures in contolling Septoria tritici blotch. Subset of the leaf images were visually assessed and erroneously analysed leaves were excluded. The source code is provided as a python package alongside.

Files in the data folder:

2018_Output_final_flag.xls

STB severity data of individual leaves in the flag leaf layer, in the experiment in year 2018

2018_Output_final_flag-1.xls

STB severity data of individual leaves in the flag-1 leaf layer (penultimate), in the experiment in year 2018

2018_Tunisia_Cultivar_Mix_Yield_Data.xls

Yield data in 2018

2018_Tunisia_cultivar_mixtures_weather.xlsx

Weather data in 2018

2019_Output_final_flag.xls

STB severity data of individual leaves in the flag leaf layer, in the experiment in year 2019

2019_Output_final_flag-1.xls

STB severity data of individual leaves in the flag-1 leaf layer (penultimate), in the experiment in year 2019

2019_Tunisia_Cultivar_Mix_Yield_Data.xls

Yield data in 2019

2019_Tunisia_cultivar_mixtures_weather.xlsx

Weather data in 2019

Cultivar_Mix_severity_means_data_all.xls

STB severity, plot means

Cultivar_Mix_severity_relative_leaf_data_all.xls

STB severity data on individual leaves, relative to the mean over means of the replicate plots of the susceptible treatment (cultivar Karim)

Cultivar_Mix_severity_relative_means_data_all.xls

STB severity data, plot means, relative to the mean over means of the replicate plots of the susceptible treatment (cultivar Karim)

Cultivar_Mix_spike_densities.xlsx

Spike densities in the plots (per square meter)

Cultivar_Mix_yield_relative_all.xls

Yield data, relative to the mean over means of the replicate plots of the susceptible treatment (cultivar Karim)