Cultivar Resistance of Korean Breeding Cut-Rose against Crown Gall by Agrobacterium tumefaciens Evaluated by an In Vitro Inoculation

Rose crown gall caused by Agrobacterium tumefaciens is a major disease that damages the production of cut -roses in Korea. The effective prevention methods for this disease include the use of resistant varieties. This study was conducted to evaluate the resistance of 58 Korean cultivars and six foreign cultivars to crown gall disease with nodal explants in vitro. Among 180 A. tu-mefaciens strains, pathogenic strain RC12 was selected as an inoculant strain. The strain RC12 was identified based on characteristics of some selective media, patho-genicity test, and polymerase chain reaction analysis. Forty rose cultivars formed tumors on explants inocu-lated with A. tumefaciens RC12. However, 24 cultivars, including 22 Korean cultivars and 2 foreign cultivars, showed resistance to A. tumefaciens RC12 without forming any tumors. Six cultivars with tumor forma-tion rates of over 30% formed initial tumors within 23 days after inoculation. Six cultivars with low tumor for-mation rates of around 5% formed initial tumors after 28 days of inoculation. It was found that gall formation rate was highly correlated with the initial gall forma-tion period. Thus, the relationship between the period of gall formation and the rate of gall formation could be useful for assessing resistance to crown gall disease. In vitro inoculation methods could be used to evaluate resistance of cut-rose cultivars to crown gall diseases.

Automated summary

This study evaluated the resistance of 58 Korean cultivars and six foreign cultivars to crown gall disease. It found that 24 cultivars, including 22 Korean cultivars and 2 foreign cultivars, showed resistance to the disease. The study also discovered a strong correlation between the gall formation rate and the initial gall formation period.