A chromosome 2 locus controls transient Agrobacterium-mediated GFP expression in rose petals

A major chromosome 2 region is associated with the genotype-dependent transient GFP expression after Agrobacterium infiltration of rose petals and provides markers for selecting permissive genotypes. Transient expression assays are valuable for testing gene function in rose, where stable transformation remains laborious and genotype-dependent. We evaluated Agrobacterium-mediated transient green fluorescent protein (GFP) expression in the petals of 96 rose genotypes and used genome-wide association analysis to identify associated host genomic regions. GFP expression was scored semiquantitatively on a scale from 0 to 4 at 3 and 5 days post-infiltration (dpi). The genotypes differed strongly in expression at both time points, and the 3- and 5-dpi scores were strongly correlated (r = 0.90, p < 0.001). At 5 dpi, the mean scores ranged from 0 to 3.98, with the cultivars Sebastian Kneipp, Friesia and Comtessa AL among the most permissive genotypes. A genome-wide association study (GWAS) of 37,161 high-quality single-nucleotide polymorphisms (SNPs) revealed a major association on chromosome 2 at 69-73 Mbp and a second peak on unanchored chromosome 0 contigs that may correspond to the same region. The top SNPs reached -log10(P) = 7.85. This identified interval represents a high-priority candidate region containing multiple potential host factors. Candidate annotations within the region include genes related to auxin transport, ubiquitin-mediated protein turnover, ribonucleic acid (RNA) metabolism, membrane-associated defence responses and nuclear transport. The results identify useful rose genotypes for petal transient assays and provide a genetic entry point for dissecting host control of Agrobacterium-mediated transient expression.