Selection for Fusarium wilt disease resistance from regenerants derived from leaf callus of strawberry.

Resistant lines of strawberry to the fungal wilt disease caused by Fusarium oxysporum f. sp. fragariae were selected strawberry plants regenerated from leaf-derived callus tissues. Regenerants were transplanted to a field heavily infested with this pathogen, and normally growing plants were selected as the putative resistant lines. Daughter plants produced vegetatively through runner formation of the lines were similarly tested in the pathogen-infested field over an additional three generations. Finally, two resistant lines were obtained from a total of 1,225 regenerants. The stable propagation of disease resistance in these lines was confirmed by directly inoculating the daughter plants with the pathogen and planting in a pathogen-infested soil. All of the control plants were efficiently infected and died within one month. The isolated plant lines grew and developed runners even after direct inoculation and produced daughter plants in this soil. Thus, the present study demonstrated the existence of somaclonal variation for disease resistance against a soil-borne fngal pathogen.