Plant grafting is one of the oldest agricultural technologies, capable of improving biotic and abiotic stress resistance, regulating plant growth, and increasing crop output and quality. Recent analytical technology has revealed that massive numbers of RNAs can move via the phloem to regulate the gene expression in the scion. However, there are currently no high-throughput methods for validating the role of these long-distance RNAs in grafting, which limits the development of rootstock resources. In this study, methodologies were developed for infection of TRSV vectors in germinating melon seeds. Efficient infection was achieved in Védrantais with completely white first-true leaves and above. Grafting was performed after the gene silencing phenotype appeared in the rootstock, resulting in gene silencing of cucurbit crops as the scion. Furthermore, different RNA viral vectors were utilized to demonstrate that the transfer of viral vectors across the graft union induced gene silencing of the scion. The approach established in this study can provide a valuable research tool for future transfer RNA function studies and rootstock breeding.

Grafting is a pivotal horticultural technique for enhancing vegetable crop productivity; however, the specific molecular mechanisms governing rootstock-induced vigor remain insufficiently elucidated. This study deciphers how bottle gourd rootstock augments growth in melon scions through an integrated approach combining physiology, transcriptomics, phytohormone profiling, and functional genetics. Phenotypic analysis confirmed a significant increase in plant height, fresh weight, and stem diameter in heterografted scions compared to controls. Transcriptome sequencing of scion apices identified 663 core differentially expressed genes (DEGs) specifically modulated by the bottle gourd rootstock. These DEGs were prominently enriched in carbohydrate metabolism and plant hormone signal transduction pathways. Consistent with this, hormonal assays revealed a specific elevation in cytokinin and ethylene levels in the scion, accompanied by the upregulation of key pathway genes, including MELO3C016881 (LOG) and MELO3C007769 (ERF060). Crucially, virus-induced gene silencing of either gene completely abolished the rootstock-conferred growth advantage. Our findings preliminarily unveil the secret behind scion vigor, providing a foundational mechanistic framework for how rootstocks reprogram scion development. The identified genes, MELO3C016881 and MELO3C007769, offer direct molecular targets for the precision breeding of superior scions in melon.