In vitro testing of strawberry resistance to Verticillium dahliae and Phytophthora cactorum

The effects of culture filtrates and homogenates of Verticillium dahliae and Phytophthora cactorum on in vitro growth and development of strawberry shoots of cvs. Elsanta, Real and Senga Sengana were investigated. The filtrates of fungal cultures as well as filtrates of homogenated mycelia did not affect strawberry shoot growth and development, whereas inoculation with mycelia of V. dahliae and P. cactorum resulted in leaf yellowing, growth inhibition, inhibition of root formation, and after several days, the death of infected plants. However, fungal growth on the media that were used was irregular and the infection rate of individual plants was very variable.Mycelial homogenates affected growth and development of strawberry shoots in a similar way to that of an intact mycelium. Because the homogenate was distributed evenly in the culturing medium, the effect was uniform and thus possible to quantitate. It was also possible to differentiate a pathogen’s inoculum potential by adequate dilution of the homogenate. The best effect was obtained with V. dahliae. Fungal homogenate inhibited root formation and shoot growth, caused leaf necrosis and death of the plants after 7–8 weeks. The reaction of the cultivars tested was similar to their sensitivity to verticillium wilt in the field.P. cactorum affected in vitro strawberry shoot growth and development in a similar way to V. dahliae, but the effect was not cultivar-dependent. Preliminary tests showed that the method developed is useful for selection of somaclonal variants resistant/tolerant to infection with these pathogens.