2017 ASHS Annual Conference

Apple is one of the most important fruit crop in the world and the value of U.S. utilized production was $3.394 billion in 2015. There are about 50 wild Malus species in the world, including four Malus species in North America, six species in Europe and Central Asia, and 40 other species in China and other Asian countries. Plant Genetic Resource Unit (PGRU), USDA-ARS focuses on the preservation of cultivated apple varieties and all the wild Malus species. The apple (Malus) collection normally are preserved as trees in the field or as open pollinated seeds from exploration and stored in -20⁰C freezer. All Malus have a very strong self-incompatibility system that prevents selfing. Apomixis is the asexual reproduction of seeds that found in many wild Malus species. The apomictic seeds have the same genotype of their parents. Eight Malus species, M. hupehensis, M. platycarpa, M. rockii, M. sargentii, M. sieboldii, M. sikkimensis, M. toringoides, and M. xiaojinensis, are known to have different level of apomixis. Since 2015, we began confirming the known apomictic Malus species in PGRU collection and investigated apomixis in other wild Malus species. We bagged the wild Malus accessions before bloom, removed the bags after fruit set, collected the fruit produced from within the bags in the fall, and extracted the seeds for storage in -20⁰C freezer. In 2016, we were able to collect apomictic seeds from M. coronaria, M. ioensis, and M. spontanea. Three bagged accessions of M. asiatica, one accession of M. fusca, M. tschonoskii, and M. yunnanensis did not produce any fruit that suggest all four species are most likely not apomictic. In 2016, we also germinated 20 apomictic seeds collected in 2015 from some Malus and comparing their genotypes with the parental genotypes using RosBREED SNP chip. We confirmed the presence of apomixis in M. coronaria, M. hupehensis, and M. sikkimensis using the RosBREED SNP chip. Apomictic seeds are small in size and weight comparing with budwood, they could be stored in freezers and maintain high viability for a long term, they could be germinate and recreate the parental genotypes, and they do not need to go through lengthy quarantine process for international exchange. We will continue identifying other wild Malus species and M. hybrids (crabapples) for the presence of apomixis. We will generate more apomictic seeds and use the apomictic seeds as alternative for preservation and exchange of wild Malus germplasm.