Apple

Resistance to apple scab


Background info
The most serious disease in apple in NW Europe     is apple scab, caused by the fungus Venturia inaequalis. Protection against this disease requires frequent applications of fungicides, both in conventional farming (synthetic fungicides) and in organic farming (sulfur, copper). More than 15 different resistance genes to this disease have been detected in apple species. These resistance genes can be introgressed into modern cultivars by means of traditional breeding. The most common used gene for apple scab resistance is the Vf-gene from Malus floribunda. It took 50 years (!) traditional breeding to bring this gene into modern varieties, and remove the majority of the unwanted genes (alleles) from M. floribunda. However, within ten years after introduction of this resistance in cultivars, the fungus could overcome the resistance. To obtain more durable resistance several resistance genes have to be accumulated in a cultivar. This is feasible through traditional breeding, but will require even more than 50 years.

In order to obtain durable resistance in a much faster way, genes for resistance to apple scab are isolated from apple species (Malus) that are used in conventional apple breeding. These genes are brought into high quality cultivars by means of cisgenesis for obtaining durable resistance. This will allow a strong reduction in fungicide applications in apple production.


ImageRed fruit flesh
Most apples have white or off-white fruit flesh. However, natural mutations have led also to apples that have red fruit flesh. This is caused by anthocyanin production in the fruit. The plants that show anthocyanin production in nearly all plants parts, such as flowers, foliage and even in the bark and root. The underlying cause is a mutation in the transcription factor MYB10 ( http://www.ncbi.nlm.nih.gov/pubmed/17181777) that controls the anthocyanin pathway. Because of the high level of anthocyanin in the fruit flesh, the apples have both an appealing appearance, and a health promoting effect through the enhanced high antioxidant capacity.
We are transferring this natural apple gene, causing red flesh, now to apple cultivars through cisgenesis.