), in which it causes witch's broom and sometimes excessive growth of prickles.

The virus is transmitted by a microscopic Eriophyid mite Phyllocoptes fructiphilus.

[4] Breeding work began with cultivar resistance trials and then morphed into bi-parental and interconnected populations for mapping disease resistance.

Recently there have been the first two studies identifying loci for resistance on both the diploid and tetraploid level using mapping populations developed at Texas A&M University Rose Breeding and Genetics Program.

[5] On the diploid level, QTL were found on linkage groups (LGs) 1, 3, 5, and 6 [6] and on the tetraploid level, QTL were found on LGs 5, 6, and 7.