Infection efficiency is a key epidemiological parameter that determines the proportion of pathogen spores able to infect and cause lesions once they have landed on a susceptible plant tissue. In this study, we present an improved method to measure infection efficiency of Zymoseptoria tritici using a replicated greenhouse experiment. Z. tritici is a fungal pathogen that infects wheat leaves and causes Septoria tritici blotch (STB), a major disease of wheat worldwide.
We devised an original experimental setup, where we (i) attached living wheat leaves to metal plates allowing for time‐resolved imaging of disease progress in planta. Since lesions were continuously appearing, expanding and merging during the period of up to three weeks, daily measurements were necessary for accurate counting of lesions. We also (ii) used reference membranes to characterize the density and the spatial distribution of inoculated spores on leaf surfaces. In this way, we captured the relationship between the number of lesions and the number of viable spores deposited on the leaves and estimated the infection efficiency of about 4% from the slope of this relationship.
Our study provides a proof of principle for an accurate and reliable measurement of infection efficiency of Z. tritici. The method opens opportunities for determining the genetic basis of the component of quantitative resistance that suppresses infection efficiency. This knowledge would improve breeding for quantitative resistance against STB, a control measure considered more durable than deployment of major resistance genes.

#### Reference_membrane_colony_density_first_experiment

First replicate of the Infection efficiency experiment. The data was collected from the reference membranes used to measure viable spore densities during the inoculation spraying. The first column, "treatment", contains numbers giving the spore concentration in the inoculated spore suspension, spores/ml. The second column, "position" refers to position of the membrane on the infection plate so that number 1 was at one end, number 2 next to it and so on, from 1 to 5. The third column, "number" identifies the counting square used to sample the colony density, arbitrary numbering of up to two squares in the first and up to three squares in the second experiment. The fourth column, "colony", gives the number of colonies counted in the square. The fifth column, "percm", gives the density of colonies within a square, colonies/cm^2. The sixth column, "size", gives the size of a square, always "1", except for highest concentration treatment of the second experiment, cm^2. Tab delimited .txt file.

Karisto_Infection_Efficiency_Zymoseptoria_Reference_membrane_colony_density_first_experiment_2018.txt

#### Reference_membrane_colony_density_second_experiment

Second replicate of the Infection efficiency experiment. The data was collected from the reference membranes used to measure viable spore densities during the inoculation spraying. The first column, "treatment", contains numbers giving the spore concentration in the inoculated spore suspension, spores/ml. The second column, "position" refers to position of the membrane on the infection plate so that number 1 was at one end, number 2 next to it and so on, from 1 to 5. The third column, "number" identifies the counting square used to sample the colony density, arbitrary numbering of up to two squares in the first and up to three squares in the second experiment. The fourth column, "colony", gives the number of colonies counted in the square. The fifth column, "percm", gives the density of colonies within a square, colonies/cm^2. The sixth column, "size", gives the size of a square, always "1", except for highest concentration treatment of the second experiment, cm^2. Tab delimited .txt file.

Karisto_Infection_Efficiency_Zymoseptoria_Reference_membrane_colony_density_second_experiment_2018.txt

#### Lesion_appearance_data_first_experiment

Lesion appearance on each leaf in the first replicate. The data was collected from daily photos by recording newly appeared lesions for every day. The first column, "treatment", contains numbers giving the spore concentration in the inoculated spore suspension, spores/ml. The second column, "density" gives the estimated vaible spore density calculated based on the reference membranes on two sides of the leaf set, spore/cm^2. The third column, "timepoint", gives the timepoint of the recording, days after inoculation. The fourth column, "leafset", identifies four leaf sets belonging to each treatment, from 1 to 4. The fifth column, "leafnumber", identifies each leaf in a leaf set, up to 8 leaves per set. The sixth column, "lesion", gives number of observed separate lesions on the image of the leaf at that date. The seventh column, "lesionappear", gives number of newly appearing lesions since the previous time point. The eighth column, "lesiontot", gives total number of appeared single lesions by that date, based on sum of appearance data of each timepoint. The ninth column, "leafsize", gives size of each leaf estimated from photos of the leaf sets taken on the day of inoculation, cm^2. The tenth column, "colony", gives estimated number of spores that landed on that leaf during the inoculation. The eleventh column, "leaflesion", gives density of all lesions appeared on the leaf (column "lesiontot"), lesions/cm^2. Tab delimited .txt file.

Karisto_Infection_Efficiency_Zymoseptoria_Lesion_appearance_data_first_experiment_2018.txt

#### Lesion_appearance_data_second_experiment

Lesion appearance on each leaf in the second replicate. The data was collected from daily photos by recording newly appeared lesions for every day. The first column, "treatment", contains numbers giving the spore concentration in the inoculated spore suspension, spores/ml. The second column, "density" gives the estimated vaible spore density calculated based on the reference membranes on two sides of the leaf set, spore/cm^2. The third column, "timepoint", gives the timepoint of the recording, days after inoculation. The fourth column, "leafset", identifies four leaf sets belonging to each treatment, from 1 to 4. The fifth column, "leafnumber", identifies each leaf in a leaf set, up to 8 leaves per set. The sixth column, "lesion", gives number of observed separate lesions on the image of the leaf at that date. The seventh column, "lesionappear", gives number of newly appearing lesions since the previous time point. The eighth column, "lesiontot", gives total number of appeared single lesions by that date, based on sum of appearance data of each timepoint. The ninth column, "leafsize", gives size of each leaf estimated from photos of the leaf sets taken on the day of inoculation, cm^2. The tenth column, "colony", gives estimated number of spores that landed on that leaf during the inoculation. The eleventh column, "leaflesion", gives density of all lesions appeared on the leaf (column "lesiontot"), lesions/cm^2. Tab delimited .txt file.

Karisto_Infection_Efficiency_Zymoseptoria_Lesion_appearance_data_second_experiment_2018.txt