Graft incompatibility in fruit crops: Causes, detection techniques and remedial measures

Graft incompatibility is a major constraint in fruit tree propagation, especially among temperate species such as apple, pear, plum, apricot, and cherry. Graft incompatibility comprises inability of scion and stock to form a strong, functional, and lasting union, leading to weak growth, vascular discontinuity, nutritional imbalances, or eventual tree death. The causes are diverse, including anatomical mismatches, physiological and biochemical disturbances, nutrient deficiencies, viral infections, and genetic factors influencing secondary metabolism and lignification. Various techniques—such as electrophoresis, phenol profiling, X-ray tomography, molecular marker analysis, and histological studies—facilitate early detection of graft incompatibility. Recent advances in genomics and proteomics have provided molecular insights into compatibility mechanisms, offering new tools for rootstock breeding and selection to ensure long-term graft success in temperate fruit crops. Remedial measures include using compatible rootstock-scion or interstock combinations, hormonal and antioxidant treatments, optimized grafting conditions, and molecular breeding for compatibility traits. Understanding incompatibility mechanisms helps in producing healthy, long-lived fruit trees and supports efficient propagation and rootstock improvement programs in commercial horticulture