Dr. Kate Evans, WSU's apple breeder, is screening both seedlings and advanced selections for fireblight resistance. TJ MULLINAX

Dr. Kate Evans, WSU’s apple breeder, is screening both seedlings and advanced selections for fireblight resistance.

Washington State University’s apple breeding program is now screening seedlings and selections for fireblight resistance.

During WSU’s annual field day at Sunrise Orchard, near Wenatchee, this week, Dr. Kate Evans, pome fruit breeder, described her program’s efforts to find new apple varieties specifically suited to Washington conditions.

The program uses genetic markers that allow Evans to identify as quickly as possible the most promising seedlings or seedlings that don’t have potential, reducing costs and improving efficiency of selection. The program stands to save tens of thousands of dollars by identifying poor quality seedlings and removing them without planting them out in the field, she said. WSU’s program was one of the first apple breeding programs in the world to apply marker-assisted seedling selection for fruit quality traits.

As well as fruit quality, target traits include regular cropping, high yields, and resistance to sunburn, powdery mildew, and fireblight. Evans said disease resistance has only recently become a focus of the program, and advanced selections are being screened for fireblight resistance, as are new seedlings. Some have similar resistance to Red Delicious, but the most disease-resistant selections don’t necessarily have the best fruit quality traits. Knowing the level of disease resistance in the material will also help Evans choose the best parents for future crosses.

The most common sources of disease resistance tend to be small, poor quality Malus species. In an effort to avoid using parents with undesirable fruit traits, Evans has been working with Dr. Jay Norelli at the U.S. Department of Agriculture in Kearneysville, West Virginia, to identify and screen other sources of fireblight resistance that have reasonable fruit traits.

Evans said a huge amount of DNA information was generated by the national RosBREED program, which was funded by the SCRI and is about to end. Graduate students at WSU have identified areas of the apple genome that control acidity and sweetness. Scientists are now mining the genetic data to identify genes relating to storage disorders.