Canopy leaf-angle architecture and leaf blade–midrib susceptibility are associated with anthracnose severity in sorghum and johnsongrass

Authors: Ahn, Ezekiel; Baek, Insuck; Prom, Louis; LIM, SEUNGHYUN - Orise Fellow; Park, Sunchung; Kim, Moon; Meinhardt, Lyndel; MAGILL, CLINT - Texas A&M University

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/22/2026
Publication Date: 6/3/2026
Citation: Ahn, E.J., Baek, I., Prom, L.K., Lim, S., Park, S., Kim, M.S., Meinhardt, L.W., Magill, C. 2026. Canopy leaf-angle architecture and leaf blade–midrib susceptibility are associated with anthracnose severity in sorghum and johnsongrass. Plant Disease. https://doi.org/10.1094/PDIS-04-26-0770-RE.
DOI: https://doi.org/10.1094/PDIS-04-26-0770-RE

Interpretive Summary: Plants defend themselves against diseases on multiple levels, from microscopic genes to the way they arrange their leaves in a field. The problem is that we often study these defenses separately, missing the bigger picture of how a plant efficiently invests its limited energy. In this study, we analyzed sorghum and its wild relative, Johnsongrass, to understand how they fight the fungal disease anthracnose. We discovered that the physical angle of the leaves acts as a "funnel," where specific shapes can drastically reduce disease by shedding infectious droplets. Inside the leaf, we found a "fortress" in the midrib vein that blocks fungal spread, a defense that works independently of the plant's shape. Most importantly, we used economic theories to evaluate if plants are investing their chemical defenses "wisely"—that is, sending help to the tissues most likely to be attacked. We found that some varieties are "smart investors" with efficient defense portfolios, while others waste resources protecting safe areas. This integrated framework serves as a powerful tool for plant breeders and pathologists. By allowing the identification of inefficient defense strategies, it enables the breeding of 'smarter' sorghum lines that optimize their natural immunity. Ultimately, this leads to more resilient crops that require fewer chemical inputs, directly benefiting farmers and enhancing global food security.

Technical Abstract: Plant defense is inherently multi-scalar, yet it is rarely modeled as an integrated system spanning physical architecture and molecular allocation. This study establishes a "Defense Architecture" framework for the Sorghum spp.-Colletotrichum sublineola pathosystem, integrating canopy geometry, tissue-specific resistance, and information-theoretic allocation metrics. Using a dataset of 28 genotypes, we developed a non-linear "canopy funneling" model (R-squared approx. 0.87) demonstrating that macroscopic leaf angle architecture is a primary determinant of disease severity, regulating inoculum interception physics. At the tissue scale, excised-leaf assays defined a tunable "midrib fortress" trait (delta-p) decoupled from canopy structure. Bridging the molecular scale, we applied Jensen-Shannon Divergence (JSD) to quantify the alignment between pathogen attack distributions (P-attack) and host gene expression portfolios (P-defense). By mapping these genotypes onto a Risk-Return plane inspired by Modern Portfolio Theory, we identified an empirical "efficient frontier" of defense strategies. These findings demonstrate that quantitative resistance is an emergent property of alignment across scales, offering a novel, interdisciplinary metric for breeding crops with optimized immunological efficiency.