Key Root Traits in the Performance of Pepper Hybrids as Rootstocks Under Low Phosphorus Conditions

Agriculture faces the challenge of increasing crop productivity while reducing dependence on finite phosphate resources and minimizing fertilizer inputs. Developing rootstocks with improved phosphorus (P) acquisition represents a promising strategy to enhance crop performance under low-input conditions. In this study, several Capsicum annuum L. hybrids, previously selected for contrasting root characteristics, were evaluated as rootstocks for two commercial pepper cultivars grown under low-phosphorus supply. Plant performance was assessed through yield, biomass production, mineral composition and comprehensive root phenotyping using both shovelomics and WinRHIZO Pro analyses. Rootstock genotype markedly influenced plant performance, although the magnitude of the response depended on the scion cultivar. While some hybrids maintained their yield and biomass under low-phosphorus conditions, others substantially reduced plant performance, highlighting the importance of rootstock–scion interactions. The results identify a combination of root traits—including greater lateral root development, increased root length and enhanced branching—associated with better plant performance under low-input conditions. These findings highlight the potential value of root architecture traits as selection criteria for pepper rootstocks and provide a basis for further evaluation of promising graft combinations under low phosphorus supplies.