In a booklet called "Rozeninzicht" published by DvP-CLO (Departement voor Plantengenetica en -veredeling - Centrum voor Landboukundig Onderzoek ~ connected to Rijkstation voor Sierplantenteelt Melle, don't know the specifics) I found this information about Melflor (so direct information of the breeders themselves):

Melflor: bred in 1982 from
"tetraploid R. rugosa seedling" x seedling

It was introduced by RVS Rijksstation voor Sierplantenteelt in 1987 as Melflor.

Further in the booklet, in the information of Melrose, a descendant of Melflor, it is mentioned that they've used a chromosome-doubled seedling of R. rugosa to create Melflor. This seedling was - very likely (mentioned elsewhere in this booklet) - created in vitro culture (so in a highly controled lab environment) treated with a colchicine solution to induce polyploidisation. So to create a tetraploid from a diploid parent.

KORtensiro is a synoniem for RoTensia. Mentioned in "Palmarès du 116 e Concours international de roses nouvelles", where it got a Certificate, as mentioned in the Awards

ADAlukrobe is a mention with source the "91e Concours international
de Roses Nouvelles de Lyon" (2021). This is a typo and should have been ADAlukobre. "Ar Duen" (or ADAlukobre) won prizes in Baden-Baden also in 2021. The pictures show practically the same rose in both winners lists.

The parentage link has a html error. I'm seeing this: < pan class="lnk small">City of Gloucester × [Polar Star (hybrid tea, Tantau, 1982)]