A Tomato Leaf Curl New Delhi Virus Vector for Virus-Induced Gene Silencing in Melon

In this study, the insert length, location within the coat protein-encoding gene, and se-quence orientation of the target fragment were optimized to construct an efficient vi-rus-induced gene silencing (VIGS) system in melon using a tomato leaf curl New Delhi virus (ToLCNDV) vector. The melon phytoene desaturase gene (CmPDS), a key regulator of chlorophyll 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 tran-scription 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 gene. These findings will be highly important for the development of novel ToLCNDV-based si-lencing vector tools and their application to functional genomics and cucurbit crop dis-ease resistance breeding research in the future.