GPM1 Strengthens Early Graft Adhesion Across Legume Crops

A newly identified small molecule could help grafted plants establish a stronger first connection, potentially expanding grafting in crops that are difficult to join. By screening 3,000 synthetic compounds, researchers discovered graft-promoting molecule 1 (GPM1), which increased early tissue adhesion in several legume species and in a cross-species graft combination. The compound also improved graft performance in two plants outside the legume family. Molecular and anatomical evidence indicates that GPM1 promotes cell-wall remodeling and callus-cell expansion at the cut surface without triggering the broad auxin response seen with conventional hormone treatment. The findings introduce a targeted chemical strategy for making early graft healing more reliable.

Grafting joins a shoot, or scion, to a rootstock so growers can combine useful traits such as disease resistance, stress tolerance, productivity, and quality. Success, however, depends on a tightly timed healing sequence: cut surfaces must adhere, callus tissue must bridge the wound, and vascular connections must be restored. These steps can be unreliable in Fabaceae, the major crop family that includes soybean, cowpea, common bean, pea, lentil, chickpea, and alfalfa. Weak adhesion at the earliest stage can leave gaps or damaged layers that disrupt later tissue reunion, even between related species. Based on these challenges, there is a need to identify practical regulators that strengthen early graft adhesion in Fabaceae crops.

Researchers from Nagoya University, Kyoto University, and Huazhong Agricultural University published (DOI: 10.1093/hr/uhag095) the study in Horticulture Research on 13 March 2026. Using a high-throughput in vitro grafting (IVG) platform, the team screened a 3,000-compound library and identified graft-promoting molecule 1 (GPM1) as a graft-promoting molecule. They then evaluated its effects across four Fabaceae species, a cowpea–soybean heterograft, and two non-legume models, combining mechanical-force measurements, RNA sequencing (RNA-seq), quantitative reverse transcription polymerase chain reaction (qRT-PCR), root-response assays, and histological imaging to determine how the compound supports early graft union formation.