Self-Organizing Maps in the Identification of Key Phenotypes of Ornamental Pepper Plants Under Contrasting Growing Conditions

Abstract High temperatures can significantly affect plant growth, development, and physiology. The identification of genotypes with desirable morphological and physiological responses under contrasting growing conditions is therefore relevant for ornamental pepper breeding. This study aimed to characterize the phenotypic responses of ten ornamental pepper ( Capsicum spp.) accessions grown under controlled (27.15 ± 1.16 °C; VPD = 2.1 ± 0.23 kPa) and high-temperature/high-VPD (39.03 ± 1.98 °C; VPD = 6.23 ± 0.85 kPa) greenhouse conditions using morphological, phenological, and physiological traits and self-organizing maps (SOMs). Differences in plant architecture and physiological responses were observed among accessions within each growth condition, while descriptive differences were also observed between conditions. In general, plant height and canopy diameter were lower under the high-temperature/high-VPD condition, while the magnitude of gas-exchange responses varied among accessions. SOM sensitivity analysis supported a 2 × 3 topology with six neurons for both conditions, based on the balance among training quality, topological preservation, and stability across 100 independent runs. Three superclasses were identified under each condition, although their composition and multivariate profiles differed between environments. CPCE 005 and CPCE 007 remained associated under both conditions and, under high-temperature/high-VPD, were characterized by compact plant architecture combined with higher relative values of gas-exchange traits. CPCE 014 showed a distinct multivariate profile under the contrasting conditions and formed an individual superclass. Overall, SOM analysis revealed a reorganization of the relationships among morphological and physiological traits between growing conditions and identified distinct accession-specific response patterns. These results highlight CPCE 005, CPCE 007, and CPCE 014 as promising accessions for further validation in breeding studies targeting ornamental peppers grown under high-temperature and high atmospheric evaporative demand.