Improving Bell Pepper Crop Performance and Fruit Quality under Suboptimal Calcium Conditions by Grafting onto Tolerant Rootstocks

Calcium deficiency or its inefficient translocation to pepper fruits leads to considerable economic loss by reducing the number of marketable fruits. The present study proposes grafting as an environmentally friendly technique to effectively reduce such loss. A commercial variety (Al-cudia F1; V) was grafted onto two pepper (Capsicum annum L.) accessions (V/A6 and V/A8), a hybrid rootstock (V/N) and was also self-grafted (V/V). All rootstock–scion combinations were cultivated under greenhouse conditions with optimal and suboptimal Ca supply and assessed for fruit yield and biomass production, gas exchange and chlorophyll fluorescence, mineral concentration in leaves and fruits as well as several fruit quality parameters. The V/N plants demonstrated an enhanced capacity for increased biomass, higher yield and number of commercial fruits and greater mean fruit weight compared with the other rootstock–scion combinations. These improvements are attributed primarily to increased intrinsic water efficiency. Additionally, a significantly higher Ca concentration in leaves was found under suboptimal Ca conditions in the V/N combination than that found in the other rootstock–scion combinations indicating a higher capacity for Ca uptake and translocation. Under the same conditions, the concentration of organic acids in fruits, such as citric and tartaric, which impact the organoleptic quality, was also higher in V/N plants. Consequently, we can conclude that grafting pepper onto tolerant rootstocks is a successful tool for ameliorating the negative impact of suboptimal Ca conditions on pepper crop performance and fruit quality.