Abstract
Shoots of 24 rose varieties were inoculated in vitro with Agrobacterium tumefaciens (crown gall bacteria) to test for their resistance. The resistance to crown gall disease was classified into two phenotypes in this study : the resistance to tumor formation and to tumor development. The variety 'PEKcougel' was the most resistant, no tumor was formed. The yellow varieties 'Dukat' and 'Golden Emblem' were not resistant to tumor formation and development, 87% and 65%, forming galls, which grew to 3.62 and 2.43 (mm×mm), respectively. Whereas, 100% and 95% of 'White Dream' and 'Purple Rain' stems developed tumors respectively ; only 7% of 'Lifirane' developed tumors. However, once infected, tumor of 'Lifirane' grew to 4.75 (mm×mm). 'Lifirane' was the most resistant to tumor formation, but it was not resistant to tumor development. In Hybrid Tea varieties, the disease incidence and tumor sizes ranged from 0 to 65% and from 0 to 4.75 (mm×mm), respectively.
