Reconstructing the pedigree of Toyama sweet cherry germplasm

Duygu Demir

doi:10.7273/000004184

Sweet cherry has been commonly grown and bred. Dr. Thomas Toyama conducted the Washington State University (WSU) Sweet Cherry Breeding Program for 20 years. Eleven commercial cultivars, 'Chelan', 'Index' 'Cashmere', 'Glacier', 'Olympus' 'Simcoe' 'Tieton', 'Benton', 'Selah', 'Kiona', and 'Cowiche', were subsequently released from this program. These cultivars and 30 extant selections are maintained currently in the WSU Roza research orchard in Prosser, WA. The origins of Toyama germplasm have not been systematically determined. The genetic history of Toyama germplasm was characterized and summarized here using Dr. Toyama's hand-written crossing records and other available pedigree information. Dr. Toyama utilized 76 parents from various geographical origins to create 212 families and 5201 germinated seeds formed from more than 90,000 pollinated flowers. Dr. Toyama commonly used parent 'Stella', and 'Napoleon' was determined to be the most commonly involved ancestor. However, the historical parentage records of Dr. Toyama's germplasm needed further investigation, as some of the recorded parentages in Toyama's breeding records book might not be correct, some parentage information was missing, and the origin of some parents was unclear. Using SNP array data for 1617 SNP markers, parentage or grandparentage was verified or deduced for most of the extant selected germplasm. The fathers of one cultivar and three selections were corrected. The results indicated that Dr. Thomas Toyama used a considerably diverse germplasm base in crossing. Complementary allelic combinations resulting from 'Stella' crossed with the French cultivars 'Early Burlat' and Moreau' might hold particular value for PNW production by imparting attributes such as self-fertility, early-season fruiting, and powdery mildew resistance. For the interesting powdery mildew-resistant selection PMR-1, PC 6658-1 or 2 ('Lambert' × 'Ebony') was determined to be the likely mother, and PC 7146-x ('Stella' × 'Moreau') was the likely father, as SNP array genotypes for the proposed grandparents completely matched PMR-1 across each of its eight phased chromosomes. 'Moreau' was determined to be the genetic source of PMR-1's powdery mildew resistance. Future studies could investigate other chromosomal segments from the parents and ancestors of Toyama's cultivars and selections that positively contribute to key horticultural traits, to further inform breeding decisions.

Reconstructing the pedigree of Toyama sweet cherry germplasm

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