Differences in Volatile Profiles Between Populations of Ceratoides lanata var. subspinosa (Rydb.) J.T. Howell

Ceratoides lanata (Rydb.) J.T. Howell, common winterfat, is valued for its nutrient content and palatability to livestock; however, the subspecies Ceratoides lanata var. subspinosa (Rydb.) J.T. Howell, ('subspinosa') is considered unpalatable. Curiously, observations of 'subspinosa' revealed several populations in central New Mexico that were heavily grazed. Volatile terpene profiles are associated with differences in palatability in many plant species. To determine whether differences in volatile profiles between 'subspinosa' populations would correlate with apparent differences in palatability, plants from 13 populations of 'subspinosa' were collected. Volatile analysis of shoot samples identified 33 compounds. Limonene, myrcene, and 3-carene were the most abundant volatiles in all populations, comprising 81 percent and 85 percent of the volatiles detected in heavily grazed and ungrazed plants, respectively. Compounds present in at least half of either the heavily grazed or ungrazed plants were subjected to a stepwise discriminate analysis of relative quantities. The analysis identified a subset of 14 chromatographic peaks (myrcene, 3-hexenol, 3-carene, AR-curcumene, limonene, n-hexanol, p-cymene, a mixture thought to contain alpha-pinene, alpha-thujene, and tricyclene, a mixture thought to contain n-decanal, and five unknowns), which may distinguish between palatable and unpalatable phenotypes. When a discriminate rule based on these chemicals was applied to chemical data from individual plants at all sites, none of the plants were misclassified. The possibility that these varied oil profiles may be used to distinguish palatable from unpalatable phenotypes is discussed.