(A)biotic stress tolerance in Ilex crenata: high soil pH and the pathogen Berkeleyomyces basicola

Ilex crenata Thunb. (Japanse hulst, Aquifoleaceae) is an evergreen, small-leaved shrub that is used in hedges and in pruned shapes. This makes I. crenata a good alternative for boxwood, that lost its popularity because of the fungal disease Calonectria and damage of the box tree moth. Replacing boxwood with I. crenata does not always go flawlessly, the problem being a difference in soil requirements. Boxwood prefers rather alkaline soils, whereas I. crenata thrives in acidic soils. In high pH soils, I. crenata shows a decrease in growth and leaf yellowing. This is ascribed to a reduced availability of the essential nutrient iron. In private gardens and public parks, the soil is alkaline because of concrete, cement and calcium-rich pavements. Besides, it seems that especially in high pH soils the fungus Berkeleyomyces basicola (before Thielaviopsis basicola, syn. Chalara elegans) causes problems. The fungus causes reduced growth and yellow discoloring of the leaves by attacking the plant roots. Infection of the fungus is visible on the plant roots as black discoloring. This project, being an initiative of the company Plant Select, studies the possibility to select for tolerant I. crenata. Tools will be developed to facilitate the breeding process and to get more insight in the interactions between plant, fungus and soil pH. The acquired knowledge and results will allow for focused and strategic breeding and the development of new varieties of I. crenata well adapted for sustainable use in gardens.