Breeding program for novel disease-resistant cider apple cultivars

Breeding program for novel disease-resistant cider apple cultivars

Summary

Despite a few challenges, the apple breeding program is off to a promising start, with successful cross-pollination and harvesting of seed from the crossing of classic apple cv. ‘Golden Russet’ with the modern disease resistant cultivar ‘GoldRush’. ‘GoldRush’ was substituted for the cv. ‘Liberty’ in this project due to heavy deer browsing of the orchard’s new ‘Liberty’ planting, making it impossible to complete the cross with that particular apple due to lack of fruit buds. ‘GoldRush’ was selected as a very good substitue for ‘Liberty’, as it has impressive disease resistance as well as being an extremely grower-friendly tree with excellent fruit and cider quality. 200 apple blossoms of ‘GoldRush’ were emasculated and subsequently hand-pollinated with “Golden Russet’ pollen. Hand pollination was largely effective, in that 131 fruits out of 200 survived ‘June drop’. The developing fruit was protected from insect and vertebrate pests by bagging, which proved effective. 108 fruits were harvested from the trees in November, and from those fruit, a total of 534 seeds were recovered. Seeds were stored in a peat / sand medium and placed into 35 degree refrigeration for an intended period of cold-stratification of 90 days.

Objectives/Performance Targets

Our performance targets for 2013 were not completely met, but the integrity of the project goals should not be impacted adversely. 

Firstly, we were forced to substitute a different cultivar of apple, ‘GoldRush’, for the intended cultivar ‘Liberty’. This was due to severe deer browsing in our young ‘Liberty’ orchard block. When it became apparent that the number of ‘Liberty’ blooms was likely insufficient for the project needs, we decided to use our ‘GoldRush’ trees as a very good alternative. ‘GoldRush’ is an excellent orchard performer which we think highly of, and it also posseses the genes for disease resistance that we had hoped to introduce from ‘Liberty’. For this reason, we feel fortunate to have a very worthy back-up cultivar like ‘GoldRush’ to substitute in this case, but more importantly can achieve the project goal of introducing additional disease resistance into a ‘Golden Russet’ type apple suited to high-quality cider production.

The second project goal not met was that the yield of seeds from 108 fruits was much lower than expected. We were hoping to get 1000 seeds, but ended up with 534. This may have been due to inadeqate pollination. However, the next benchmark in the project relates to seed germination, so if we get a reasonably high rate of germination (60-80%), we can still end up with close to our goal of between 300-400 seedlings.

Accomplishments/Milestones

Overall, despite the initial setbacks caused by deer browsing and lower than expected seed yield, the project remains on track to grow out and evaluate seedling apple crosses. With the storage of 534 succesfully harvested seeds presently undergoing cold-stratification, we consider the most important milestone for project year 2013 to have been successfully passed.

Impacts and Contributions/Outcomes

Collaborators: