Comparisons of Anatomical Characteristics and Transcriptomic Differences between Heterografts and Homografts in Pyrus L.

Pear (Pyrus L.) is an important temperate fruit worldwide, and grafting is widely used in pear vegetative propagation. However, the mechanisms of graft healing or incompatibility remain poorly understood in Pyrus. To study the differences in graft healing in Pyrus, the homograft Qingzhen D1/Qingzhen D1 and the heterograft QAUP-1/Qingzhen D1 as compatibility and incompatibility combinations were compared. Anatomical differences indicated the healing process was faster in homografts than in heterografts. During the healing process, four critical stages in graft union formation were identified in the two types of grafts. The expression of the genes associated with hormone signaling (auxin and cytokinins), and lignin biosynthesis was delayed in the healing process of heterografts. In addition, the PbBglu13 gene, encoded beta-glucosidase, was more highly up-regulated in heterografts than in homografts to promote healing. Meanwhile, the most of DEGs related starch and sucrose metabolism were found to be up-regulated in heterografts; those results indicated that cellulose and sugar signals were also involved in graft healing. The results of this study improved the understanding of the differences in the mechanisms of graft healing between homografts and heterografts.

Automated summary

This study compared the graft healing process between homografts and heterografts in pear trees. It found that the healing process was faster in homografts. The expression of genes associated with hormone signaling and lignin biosynthesis was delayed in heterograft healing, while the beta-glucosidase gene was highly up-regulated to promote healing. Furthermore, genes related to starch and sucrose metabolism were up-regulated in heterografts, suggesting the involvement of cellulose and sugar signals in graft healing.