ISSUE: New strawberry varieties with improved fruit quality will lead to increased consumer enjoyment and consumption, and will contribute to the profitability and sustainability of the U.S. strawberry industry. To meet this challenge, new strawberry varieties are needed that are high yielding due to continuous flowering and that are resistant to soil pathogens that cause serious diseases like root rot. However, breeding new strawberry varieties is slow and inefficient. Predicting which selections will be the best parents is difficult. Thousands of seedlings must be grown and tested in the field to identify the few with commercial potential.

WHAT HAS BEEN DONE: Strawberry breeders in California, Florida, Michigan, New Hampshire, and Oregon evaluated more than 900 individuals including old and new varieties, wild plants from North and South America, elite breeding parents, and experimental crosses from the Netherlands, United Kingdom, Spain, France, and the United States. This data was used to enable the development of genetic tests that strawberry breeders can use to verify plant identity and determine the best parents to combine, giving them the best seedlings to advance. A genetic test was developed to predict resistance to one of the sources of root rot resistance. This genetic test enables breeders to identify seedlings that have this source of resistance without the need to carry out expensive, time-consuming disease inoculation tests.

IMPACT: As a result of genetic testing of strawberry selections in the USDA-ARS Corvallis, Oregon and Michigan State University breeding programs and extensive performance evaluations of these strawberries:

• Forty-two individuals from 13 crosses were discarded because DNA tests identified them as derived from unintended parentage.
• For several important varieties used as parents, plants from multiple sources were found to be different genetically and therefore somehow mislabeled during cultivation and breeding use.
• Fourteen strawberry selections were identified as having new sources of root rot resistance.
• Two interspecific hybrids of wild strawberries were found which are strongly continuously flowering in multiple environments (California, Michigan, and Oregon). These individuals will provide breeders with a unique genetic source of repeat flowering.