CBGG

Horseradish (Armoracia rusticana Gaertner, Meyer & Scherbius) is often times described as sterile because the flowers it produces does not generally form pods filled with seeds or only develops seed in very limited quantities. Some past research have concluded that horseradish is highly sterile due male sterility resulting from non-viable pollen, but another possible mechanism for the perceived improper seed set and development in horseradish is self-incompatibility (SI), related to mate limitation. Thus, a study was designed to further document horseradish pollination and fertilization by evaluating the self- and cross-compatibility of several horseradish clones collected from different locations in the world with two Illinois, USA tester clones (15K as pollen acceptor and 9705 as pollen donor). All clones evaluated had viable pollen, indicating that pollen sterility should not have been an issue in preventing pollination and eventual seed development in these clones. Most horseradish clones obtained from Europe and Russia provided self-rejection responses to their own pollen, although three accessions evaluated did have some minimal capsule set and seed development (874A from England; 784A from Moscow, Russia; and 866A from Laufener, Germany). Most clones evaluated also provided compatible pollen with 15K for capsule formation, ranging from 39% to 100%. Additionally, most clones were compatible with 9705 pollen, although some had higher compatibility success for capsule set and development. This research indicates that mate limitation appears to have played a significant role in this crop being originally identified as sterile from the lack of seed production. If the most widely grown clone in a particular locale or region is SI, then horseradish clones in that area would appear sterile since the only mate nearby would be itself. This research using horseradish clones from various regions of the world further suggests that the once perceived sterility in this plant species is most likely due to SI pollination and fertilization systems that are typical for the Brassicaceae family.

Armoracia rusticana; asexual propagation; horseradish; pollen; pollination; self-incompatibility