Browsing by Subject "mansikan härmä"

The powdery mildew of strawberry (Podosphaera macularis) causes yield losses in both fields and under glass. The ability to resist the infection of powdery mildew is a desirable attribute in the breeding of new cultivars. The assessment of powdery mildew resistance of cultivars by laboratory tests would give tools to quickly separate resistant cultivars from susceptible in the process of plant breeding. The purpose of this study was to compare the powdery mildew resistance of strawberry cultivars demonstrated in laboratory and greenhouse tests, and to evaluate the methods used. In addition, it was tested in the F2 crossing populations of wild strawberry if the ability to resist powdery mildew could be genetically linked to a phenotypic character of runner production or the flowering habit. The ability to resist powdery mildew of the garden and wild strawberry was assessed in laboratory tests by inoculating detached leaflets of in vitro grown plants with conidia of powdery mildew, and incubating them in closed Petri-dishes with moist filter paper for two weeks. The symptoms of powdery mildew were assessed visually from the leaflets. Garden and wild strawberry plants were exposed to powdery mildew in the greenhouse, and the symptoms were assessed during an eight-week period. The detected differences between the garden strawberry cultivars were compared to the laboratory results. The differences between individual plants were observed in the F2 crossing populations of wild strawberry. The runnering/non-runnering trait and the flowering habit were also defined, and the connection of these traits to the powdery mildew resistance was tested. Runnering was observed from the plants in the greenhouse, and the flowering habit was determined in the laboratory with specific markers. The comparability between the laboratory and greenhouse tests of garden strawberry was poor. The variance in the laboratory data was great due to the difficulties in the controlling of the conditions, and the quality of the inoculum. Probably because of these problems the laboratory tests on the wild strawberry failed completely. In the greenhouse there could be seen differences between the individual plants of the F2 populations of wild strawberry. The differences were not able to be statistically linked to the habit of runner production or the flowering habit, but a hint of a weak connection could be observed between the runner production and the powdery mildew resistance. Stable conditions and the quality and freshness of the inoculum have a great role in the success of laboratory tests in assessing powdery mildew resistance. In the greenhouse the disease pressure should be kept limited, so that the differences in the resistance to powdery mildew can be assessed. The connection between the runner production and the powdery mildew resistance could be experimented in the future with a bigger test group.