Article (magazine)  (Feb 2021)  
 
One KSN allele with a 9 kb Copia insertion was found to be identical to that from continuously flowering Rosa chinensis Old blush. The other allele was found to be a functional wild-type allele. The overall expression of KSN was closely linked to the floral transition, and it was significantly repressed in continuously flowering Purple branch compared with OF Plena.....
To date, the origin of Purple branch remains unclear, but it is generally considered to have derived from an interspecific cross between R. rugosa Plena and Rosa davurica. Intriguingly, its presumptive parents are OF rose species (Fig.1); thus, its CF behavior remains unexplained..... R. rugosa Purple branch, R. rugosa Plena, R. davurica and R. chinensis Old blush were grown in the rose resource nursery of Nanjing Agricultural University (Nanjing, China) under natural conditions.....
We cloned the KSN promoter and coding region from continuously flowering Purple branch, OF Plena, and R. davurica using the same primers that were previously used to amplify this region in R. chinensis Old blush....Subsequent sequence alignment showed that the sequence of one of the KSN alleles from Purple branch was almost the same as that from Plena, except for a few SNPs and a 44 bp insertion in the second intron. The other allele was similar to that from CF R. chinensis Old blush and contained a Copia retrotransposon insertion in the second intron (Figs. 2c, e and S1). These results indicate that the diploid Purple branch is heterozygous for KSN (KSN-Copia/KSN-Wt-Pb) (Fig.2f). Because neither allele was similar to that of R. davurica, our work contradicts the notion that Purple branch was derived from an interspecific cross between R. rugosa Plena and R. davurica.