Advancing Cider Apple Breeding via Wild Relative Contributions

Tymon Marell James

doi:10.7273/000005090

The U.S. hard cider industry is growing quickly, and traditional cider apple cultivars are in need of improvement to meet industry and consumer demands. Alleles that impart improved production and quality characteristics are harbored in wild Malus species and could be exploited via breeding. However, the long juvenility period in apple hampers breeding new cider apple cultivars. Future plant breeders need education and experience in modern plant breeding techniques to become effective practitioners. This work aimed to advance cider apple breeding via wild relative contributions while demonstrating an approach for training future plant breeders. The objectives of the first study were to describe the approaches, outcomes, and student involvement to date of the student-run Palouse Wild Cider apple breeding program (PWCabp). Over the past nine years, more than 20 undergraduate and graduate students gained experience in the decisions and operations of a fruit breeding program. Recent advances included refining the twelve target attributes, establishing field trials, and identifying and propagating two promising high-bitterness selections. The objectives of the second study were to identify trait loci involved in short juvenility by generating biparental families with a common maternal parent (M. × zumi ‘Calocarpa’) segregating for juvenility period and raising them in a greenhouse with one simulated season every seven months, genotyping (using a 20K apple SNP array) and phenotyping for juvenility period and several other morphological traits, and conducting QTL analysis. In both families (paternal parents M. sieboldii MA #1255 and M. baccata ‘Manchurian’), no significant evidence was detected for QTLs associated with short juvenility, perhaps because many small-effect loci control the trait in these species, lack of heterozygosity, or insufficient genome coverage. Some QTL evidence was detected for other morphological traits. The PWCabp could serve as a model to provide such educational opportunities at other institutions and will continue to exploit wild Malus relatives. Information gained from the short juvenility study will help guide future genetic studies involving apple wild relatives. This work highlighted some valuable contributions from wild species in breeding, identified some challenges, and successfully contributed to advancing cider apple genetic improvement via wild relative contributions.

Advancing Cider Apple Breeding via Wild Relative Contributions

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