Canopy leaf-angle architecture and leaf blade-midrib susceptibility are associated with anthracnose severity in...

Sorghum anthracnose, caused by Colletotrichum sublineola, is a rain-splash-dispersed disease for which canopy structure and tissue-specific susceptibility can shape observed severity. Here, we re-analyzed previously published sorghum-johnsongrass datasets to quantify associations between leaf-angle architecture, excised-leaf susceptibility, and greenhouse disease outcomes. Basal leaf-angle profiles measured at the 8-leaf stage were available for 28 genotypes; among these, 14 genotypes had greenhouse anthracnose severity measurements for C. sublineola isolate FSP35. Across the 14 genotypes with greenhouse severity measurements, a quadratic model using canopy 'droop' slope (angle versus leaf position) accounted for 87.0% of between-genotype variation in greenhouse severity (R² = 0.870), supporting substantial architecture-disease association within this dataset. In excised-leaf assays (FSP35), midrib tissues generally exhibited equal or lower severe-infection probabilities than lamina tissues, and pooled ordinal analysis supported a modest overall tissue effect, although excision-related physiological effects cannot be excluded. As an exploratory extension, we summarized qRT-PCR responses from a limited marker panel to estimate tissue-level defense-response fractions in four genotypes inoculated with isolate FSP53. We then compared these defense fractions against normalized tissue-level severe-infection distributions using Jensen-Shannon divergence. Because the infection and response data were generated from different isolates and assay conditions, we interpret this comparison strictly as a descriptive alignment metric rather than a causal measure. Together, these results identify canopy leaf-angle descriptors and leaf blade-midrib susceptibility contrasts as quantitative traits that can be prioritized for hypothesis-driven validation and disease screening under field-relevant conditions.