Antibacterial Properties of Plant Extracts against the Pathogen of Rosaceae Plants Erwinia amylovora

Erwinia amylovora is a devastating pathogen of plants of the family Rosaceae causing blight on the leaves, shoots, and flowers. Orchard trees suffer the most, however, other plants, like roses, strawberries, raspberries, and hawthorn, can also be affected. Due to the extreme use of chemicals for plant protection, alternatives like plant extracts have been studied recently. Some of the research shows a good potential to control plant diseases, however, only a symbolic number of plant species have been tested, and also, on a restricted number of pathogens. The information on the activity of plant extracts against E. amylovora is scarce. In this study, we prepared plant extracts from fifteen plant species and tested them against the plant pathogenic bacteria E. amylovora. The products were prepared by Soxhlet extraction with methanol and the following concentration according to an established procedure. The finished products were diluted and tested for antibacterial activity in different concentrations in vitro against seven reference strains of E. am¬ylovora, isolated from different hosts, such as pear, apple, quince, aronia, hawthorn, strawberry, and musk strawberry. Extracts from the roots of Geranium macrorrhizum and fruits of Chaenomeles sp. genotypes showed promising potentialities for further experiments on the control of E. amylovora.