Location: Plant Genetic Resources Unit (PGRU)
Project Number: 8060-21000-033-000-D
Project Type: In-House Appropriated
Start Date: Mar 29, 2023
End Date: Mar 28, 2028
Objective 1: Characterize important rootstock traits in apple using genetic and genomic approaches. Sub-objective 1.A: Characterize genetic and gene expression components of dwarfing and early bearing induction traits Sub-objective 1.B: Characterize genetic and gene expression components of rootstock connected tree decline caused by apple viruses. Objective 2: Breed improved apple rootstocks that perform well in diverse apple growing environments while maintaining standards for rootstock induced dwarfing, early bearing, yield efficiency, disease resistance, and overall field performance. Sub-objective 2.A: Perform all breeding and evaluation stages involved in the 15-35 year process of developing new rootstocks with the assistance of recently developed breeding tools, such as marker-assisted selection and micro-propagation.
Apples are the most consumed fruit in the United States, featuring more than 26,000 producers and a farm-gate value of about $3.2-4 billion for apples produced in the U.S (usapple.org). To keep up with the demand for traditional and novel apple cultivars, apple growers plant 15-30 million trees yearly to replace obsolete orchards and transition to new cultivars. Apple growers face increasing challenges with increased disease pressure (fire blight, viruses, and replant disease) and the effects of climate change (water availability, temperature fluctuations, etc.). A proven solution to these challenges has been to breed new types of apple trees that can overcome these challenges naturally. All newly planted apple trees are made of two different parts, the rootstock cultivar, which provides the foundation of the tree and interacts with soil, and the scion cultivar, which is joined to the rootstock by way of grafting. The research in this project involves breeding new apple rootstocks that feature improvements regarding disease resistance, productivity, and fruit quality; when compared to conventional rootstock technologies. Breeding new apple rootstocks requires a lengthy and intensive effort that utilizes some of the best genetic marker technologies and multiple rounds of decade-long replicated field trials that match the life span of intensive apple orchards (12-19 years). Apple rootstock productivity is the result of two-component traits which are not well understood: dwarfing (or vigor control) and early-bearing, which, when combined, allow apples to be produced efficiently. Another component that is not well understood is tolerance to apple viruses, which can cause the decline and death of apple trees. Research is needed to understand both traits. The approach includes several designed and already planted field and greenhouse experiments that will produce necessary performance data which, when combined with genomic and other molecular data, will be used to develop new solutions (including new apple rootstocks) that will provide stakeholders with improved options for increased productivity and profitability of apple orchards.