Enhanced Resistance to Verticillium dahliae in Transgenic Strawberry Plants Expressing a Lycopersicon chilense Chitinase Gene

Abstract

A chitinase gene (pcht28), isolated from Lycopersicon chilense, was transferred into `Joliette' strawberry using a stipule regeneration method and Agrobacterium-mediated gene transfer technique. Stipules showed a high rate of shoot regeneration (>90%) through direct or indirect organogenesis. Stipules were cocultured with a transformation plasmid in which pcht28 was under the control of the CAMV 35S promoter. A high tendency in production of chimaeric shoots was observed. Shoots which did not show any sign of bleaching after several subcultures in kanamycin containing medium were considered as stable transformants. These shoots were successfully rooted in the presence of 50 μg·mL-1 kanamycin. Transgenic nature of the plants was confirmed by PCR as well as Southern blot analysis. Constitutive expression of the chitinase gene was demonstrated by Northern analysis. In growth chamber studies, the transgenic strawberry plants which expressed pcht28 had significantly higher resistance to Verticillium dahliae as compared to nontransgenic controls. These results demonstrate that pcht28 plays a role in defense against this fungal disease in strawberry.