A Begomovirus solanumdelhiense Vector for Virus-Induced Gene Silencing in Melon

In this study, the insert length, location within the coat protein-encoding gene, and sequence orientation of the target fragment were optimized to construct an efficient virus-induced gene silencing (VIGS) system in melon using a Begomovirus solanumdelhiense vector. Existing systems are mostly RNA viruses, requiring in vitro synthesis of viral strands that are prone to degradation, although they exhibit high infectivity and stability in cucurbit hosts and ease of manipulation. This vector was selected for its more stable genome structure and these advantages. The melon phytoene desaturase (CmPDS), a key gene of carotenoid biosynthesis, was selected as a reporter gene to evaluate the effects of the VIGS system. Our results revealed that the melon leaves in all the VIGS treatments exhibited a typical photobleaching phenotype at 21 days post-inoculation. Moreover, reverse transcription quantitative real-time PCR revealed a significant reduction in the mRNA levels of PDS in melon. The highest silencing efficiency (lowest PDS mRNA levels) was achieved by the VIGS vector harboring a 165 bp CmPDS fragment at the 3' end of the AV1. These findings not only establish a more efficient VIGS protocol for melon but also provide a foundation for developing novel virus-based silencing tools applicable to functional genomics and cucurbit crop improvement, particularly for traits requiring precise gene expression modulation such as disease resistance and fruit quality.