Sorbitol promotes the graft healing process in pears

Pear propagation is primarily achieved through asexual reproduction via grafting. During the graft union healing process, there is metabolic exchange between the rootstock and the scion. However, a multi-omics systematic study on the role of sugar in the graft union healing process has not been reported. In this study, using micrografting techniques, we comparatively analyzed the metabolic changes during the healing process in homograft and heterograft of pear through metabolomics and transcriptomics. We found significant differences in sugar metabolism pathways after grafting. In the fructose and mannose metabolic pathways, sorbitol exhibited opposite trends in homograft and heterograft. Subsequent transcriptomics analysis confirmed that these metabolite changes were caused by differential expression of related synthetic and converting enzyme genes. Furthermore, spatial metabolomics identified sorbitol accumulation in the scion after homologous grafting. To further verify the role of sorbitol, exogenous sorbitol treatment was applied, revealing that it enhanced tissue adhesion, shortened the time required for callus growth, promoted high expression of xylem formation genes and cambium differentiation genes, and facilitated the reconnection of xylem and phloem, thereby playing a positive role in graft union healing. This study systematically analyzed changes in sugar metabolism during the grafting process and confirmed that sorbitol can promote graft union healing.