The native, perennial shrub American hazelnut (Corylus americana) is cultivated in the Midwestern U.S. for its significant ecological benefits, as well as its high-value nut crop. Perennial crops are a long-term breeding effort, and would benefit from the use of genetic data in selection to reduce breeding cycle time. In addition, high-throughput phenotyping methods are essentially to the efficient and accurate screening of large breeding populations. This study reports novel advances in both of these domains, for American (C. americana) and interspecific hybrids between European (C. avellana) and American hazelnuts. Two populations of hazelnuts, one composed of C. americana and one composed of C. americana x C. avellana hybrids, were phenotyped over the course of two years in two locations using a digital imagery-based method for quantifying morphological nut and kernel traits. This data was used to perform composite interval mapping (CIM) using a recently released genetic map, and genomic prediction using a newly-available chromosome-scale reference genome for C. americana. Multiple QTL were detected for all traits analyzed, with an average total R2 of 52%. Genomic prediction exhibited high accuracy, with an average correlation coefficient between genotypic values and phenotypic observations of 0.78 across both environments. These results suggest that incorporating genetic data in selection is a tenable method for improving genetic gain for highly-polygenic traits in hazelnut breeding programs.
Brainard et al. (Mon,) studied this question.