Physiological and Molecular Insights into Citrus Rootstock–Scion Interactions: Compatibility, Signaling, and Impact on Growth, Fruit Quality and Stress Responses

Grafting is a crucial horticultural propagation technique that plays a vital role in citrus production and research. Selecting compatible rootstock–scion combinations is essential for achieving high yields and superior fruit quality in citrus cultivation. This paper reviews recent advances in the physiological and molecular mechanisms involved in rootstock–scion interactions in citrus, with a focus on (1) commonly used rootstocks, (2) graft compatibility, (3) signal molecule transport at the graft union, and (4) the effects of rootstock–scion interactions on citrus growth, nutrient absorption, fruit quality, and responses to both biotic and abiotic stresses. Additionally, we prospected the future research direction and practical applications of rootstock–scion interactions.