Plant hormone ethylene plays a key role in the ripening process of climacteric fruits, but its influence on maturation of non-climacteric fruits is not clear. Enhancing effect of ethylene on ripening was shown in case of citrus species belonging to the same non-climacteric group as strawberry, but genes coding enzymes of ethylene production have not been isolated yet from strawberry, in spite of the fact that ethylene inhibitors could improve the storability of strawberry. Our aim is to analyse the activity of ACC-synthase gene, key enzyme of ethylene biosynthesis in higher plants in order to reveal the role of ethylene in ripening of non-climacteric fruits like strawberry using control cultivars and their transgenic lines transformed with antisense ACC-synthase constructs. Apple derived ripening related cDNA clones will be applied for transformation purposes and gene expression analyses.