Growth and Biochemical Activity of Passion Fruit Seedlings in Scion/Rootstock Combinations Under Salt Stress

The yellow passion fruit is a key crop in irrigated areas of Northeast Brazil, but production is challenged by limited water availability and high salinity in groundwater used for irrigation. This study evaluated the effects of grafting Passiflora edulis f. flavicarpa Degener (E) onto P. foetida L. (F) rootstock to reduce the impact of saline stress. Conducted in a greenhouse using a 3 × 2 factorial design with four replications, the experiment tested three grafting combinations (F + F, E + E and E + F) under two salinity levels (0.5 and 6.0 dS m−1). Key parameters measured included SPAD index, soluble protein content, hydrogen peroxide (H2O2) levels, catalase enzyme activity, plant height, and leaf number. Salinity significantly reduced plant height, especially at 6.0 dS m−1. The E + E combination had the highest protein content in roots (23.8%). However, grafting P. edulis onto P. foetida (E + F) enhanced catalase activity and reduced H2O2 accumulation, indicating improved tolerance to salt stress. The findings suggest that using P. foetida as a rootstock may help mitigate oxidative damage and promote better physiological performance of yellow passion fruit under saline conditions, offering a strategy to sustain cultivation in stress-prone environments.