Data from: Ranking quantitative resistance to Septoria tritici blotch in elite wheat cultivars using automated image analysis

Quantitative resistance is likely to be more durable than major gene
resistance for controlling Septoria tritici blotch (STB) on wheat. Earlier
studies hypothesized that resistance affecting the degree of host damage,
as measured by the percentage of leaf area covered by STB lesions, is
distinct from resistance that affects pathogen reproduction, as measured
by the density of pycnidia produced within lesions. We tested this
hypothesis using a collection of 335 elite European winter wheat cultivars
that was naturally infected by a diverse population of Zymoseptoria
tritici in a replicated field experiment. We used automated image analysis
(AIA) of 21420 scanned wheat leaves to obtain quantitative measures of
conditional STB intesity that were precise, objective, and reproducible.
These measures allowed us to explicitly separate resistance affecting host
damage from resistance affecting pathogen reproduction, enabling us to
confirm that these resistance traits are largely independent. The cultivar
rankings based on host damage were different from the rankings based on
pathogen reproduction, indicating that the two forms of resistance should
be considered separately in breeding programs aiming to increase STB
resistance. We hypothesize that these different forms of resistance are
under separate genetic control, enabling them to be recombined to form new
cultivars that are highly resistant to STB. We found a significant
correlation between rankings based on automated image analysis and
rankings based on traditional visual scoring, suggesting that image
analysis can complement conventional measurements of STB resistance, based
largely on host damage, while enabling a much more precise measure of
pathogen reproduction. We showed that measures of pathogen reproduction
early in the growing season were the best predictors of host damage late
in the growing season, illustrating the importance of breeding for
resistance that reduces pathogen reproduction in order to minimize yield
losses caused by STB. These data can already be used by breeding programs
to choose wheat cultivars that are broadly resistant to naturally diverse
Z. tritici populations according to the different classes of resistance.