GBS-Based Deconvolution of the Surviving North American Collection of Cold-Hardy Kiwifruit (Actinidia spp.) Germplasm

Plant germplasm collections can be invaluable resources to plant breeders, provided they are well-characterized. After 140 years of acquisition and curation efforts by a wide and largely non-coordinated array of private and institutional actors, the current US collection of cold-hardy kiwifruit (Actinidia spp.) is rife with misclassifications, misnomers, and mix-ups. To facilitate the systematic improvement and resource-efficient curation of these species of long-recognized horticultural potential, we used genotyping-by-sequencing (GBS) data to deconvolute this historic collection. Evaluation of a total of 138 accessions (103 A. arguta, 28 A. kolomikta, and 7 A. polygama) with an interspecific set of 1,040 high-quality SNPs resulted in clear resolution of the three species. Intraspecific analysis (2,964 SNPs) within A. arguta revealed a significant level of redundancy (41.7%; only 60 unique genotypes out of 103 analyzed) and a sub-population structure reflecting likely geographic provenance, phenotypic classes, and hybrid pedigree. For A. kolomikta (3,425 SNPs), the level of accession redundancy was even higher (53.6%; 13 unique genotypes out of 28 analyzed); but no sub-structure was detected. Numerous instances were discovered of distinct genotypes sharing a common name, different names assigned to the same genotype, mistaken species assignments, and incorrect gender records, all critical information for both breeders and curators. In terms of method, this study demonstrates the practical and cost-effective use of GBS data to characterize plant genetic resources, despite ploidy differences and the lack of reference genomes. With the recent prohibition on further imports of Actinidia plant material into the country and with the active eradication of historic vines looming, this analysis of the US cold-hardy kiwifruit germplasm collection provides a timely assessment of the genetic resource base of an emerging, high-value specialty crop

The role of Schmidt 'Antonovka' in apple scab resistance breeding

'Antonovka' has long been recognised as a major source of scab (Venturia inaequalis) resistance useful for apple breeding worldwide. Both major gene resistances in the form of the Rvi10 and Rvi17 and quantitative resistance, collectively identified as VA, have been identified in different accessions of 'Antonovka'. Most of the 'Antonovka' scab resistance used in apple-breeding programmes around the world can be traced back to Schmidt 'Antonovka' and predominantly its B VIII progenies 33,25 (PI 172623), 34,6 (PI 172633), 33,8 (PI 172612) and 34,5 (PI 172632). Using genetic profile reconstruction, we have identified "common 'Antonovka' " as the progenitor of the B VIII family, which is consistent with it having been a commercial cultivar in Poland and the single source of scab resistance used by Dr. Martin Schmidt. The major 'Antonovka' scab resistance genes mapped to date are located either very close to Rvi6, or about 20-25 cM above it, but their identities need further elucidation. The presence of the 139 bp allele of the CH-Vf1 microsatellite marker known to be associated with Rvi17 (Va1) in most of the 'Antonovka' germplasm used in breeding suggests that it plays a central role in the resistance. The nature and the genetic relationships of the scab resistance in these accessions as well as a number of apple cultivars derived from 'Antonovka', such as, 'Freedom', 'Burgundy' and 'Angold', are discussed. The parentage of 'Reglindis' is unclear, but the cultivar commercialised as 'Reglindis' was confirmed to be an Rvi6 cultivar