Highly efficient, genotype‐independent transformation and gene editing in watermelon (Citrullus lanatus) using a chimeric ClGRF4‐GIF1 gene

Summary Efficient genetic transformation has the potential to advance research and breeding in watermelon ( Citrullus lanatus ), but regeneration from tissue culture remains challenging. Previous work showed that expressing a fusion of two interacting transcription factors, GROWTH‐REGULATING FACTOR4 (GRF4) and GRF‐INTERACTING FACTOR1 (GIF1), improved regeneration in wheat ( Triticum aestivum ). By overexpressing a chimeric fusion of ClGRF4 and ClGIF1 , we achieved highly efficient transformation in watermelon. Mutating the mi396 microRNA target site in ClGRF further boosted the transformation efficiency up to 67.27% in a genotype‐independent manner. ClGRF4‐GIF1 can also be combined with clustered regularly interspaced palindromic repeats (CRISPR)/CRISPR‐associated protein 9 (Cas9) genome editing tools to achieve highly efficient gene editing in watermelon, which we used to successfully create diploid seedless watermelon. This research thus puts forward a powerful transformation tool for future watermelon research and breeding.