Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 25, 1995
Publication Date: N/A
Interpretive Summary: Some white clover plants produce hydrocyanic acid. These plants are called cyanogenic plants. This acid is disliked by insects that eat clover leaves, but has no harmful effects on cattle or other animals. The white clover seed collection was evaluated to determine which entries have cyanogenic plants. One third of the plants evaluated were cyanogenic. The most cyanogenic plants came from Morocco, Spain, Portugal, France, and Turkey. They were collected in areas with high winter temperatures and low summer rainfall. Scientists can use this information to collect and develop cyanogenic white clover that will be resistant to insect feeding.
Cyanogenesis (HCN), the production of hydrocyanic acid, is a trait in white clover (Trifolium repens L.) controlled by alleles at two unlinked loci, Ac and Li. Objectives were 1) to determine the proportion of HCN plants in U.S. white clover accessions, 2) to determine how representative the core subset was of the entire collection for cyanogenesis, and 3) to determine the relationship of HCN to collection site climate. Two to three leaves per plant from 20 plants of 548 white clover accessions were harvested and the presence or absence of HCN was determined by the picric acid test. The U. S. germplasm collection was predominantly acyanogenic. Accessions with the most HCN plants were collected in Morocco, Spain, Portugal, France, and Turkey while the least HCN plants were collected in China, Romania, Russia, Kazakhstan, Croatia, Bosnia-Herzegovina, and Slovenia. Geographic stratification with random sampling was an effective method of developing a core subset, as the white clover core subset was representative of the entire collection for HCN. HCN frequency was greater in accessions collected at low altitudes and at sites with high winter temperatures, lower summer precipitation, greater spring cloudiness (% sunshine), and less snow cover.