Maize Canopy Architecture and Chili Shade Tolerance in Tropical Intercropping Systems: A Systematic Review of Microclimate Modification, Genetic Adaptation, and Breeding Targets

Abstract

Background Intercropping benefits are strongly context-dependent, shaped by physiological compatibility between component species rather than spatial arrangement alone. In maize-chili systems, this compatibility is governed by two historically separate literatures: maize canopy architecture, which determines shading, and chili shade tolerance, which determines companion-crop response. This review synthesizes both bodies of evidence within a single mechanistic framework linking canopy-driven light and microclimate modification to chili morphology, physiology, genetics, pest and disease dynamics, and postharvest quality. Methods Following PRISMA 2020 and ROSES guidance, we searched Scopus (maize block, n=692; chili block, n=60) and PubMed as a complementary source for molecular mechanisms (n=91), yielding 843 records (828 after deduplication). Screening followed a single documented pass against pre-defined criteria: 129 records were excluded at title/abstract screening, 24 were retained for contextual citation only, and 107 more were excluded at secondary screening, yielding a working corpus of 566 records. Findings were synthesized narratively (SWiM) across five thematic lenses. Results Maize canopy architecture is genetically characterized at the single-gene level ( lac1 , loci linked to lg1 ), but rarely designed for companion shading. Chili shade tolerance is strongly genotype-dependent, with up to 17-fold differences in capsaicinoid content among cultivars under identical shade. Direct evidence combining both commodities remains scarce, concentrated within one research cluster. Canopy-modified microclimate alters pest/disease dynamics asymmetrically (e.g., Pepper veinal mottle virus incidence fell from 75% to <17% under intercropping), while postharvest quality follows a shade-optimum curve rather than a linear response. Conclusions The maize canopy-architecture and chili shade-tolerance literatures are mechanistically convergent, sharing a common photoreceptor-mediated signaling pathway, yet remain rarely integrated experimentally. We define ideotype targets for both commodities and argue that intercropping-adapted breeding should treat genotype × genotype compatibility rather than independent single-species optimization as its primary selection unit, a reframing with direct implications for maize and chili breeding programmes targeting tropical intercropping systems.

The authors' abstract, as published at the source. F1000Research, 2026 · DOI ↗