EXPERIMENTAL HYBRIDIZATION OF XANTHIUM STRUMARIUM (COMPOSITAE) FROM ASIA AND AMERICA. II. SESQUITERPENE LACTONES OF F₁ HYBRIDS

Abstract

Effects of hybridization on sesquiterpene lactones in Xanthium strumarium were studied for clues to the relationship of Old and New World populations. In crosses between indigenous Asiatic plants in the “strumarium” morphological complex and various American complexes that produce xanthinin as a major sesquiterpene lactone, the F1 hybrids contained xanthinin and the related compounds, xanthanol, xanthatin, and xanthinosin. In other crosses with various American complexes that produce xanthumin, the stereoisomer of xanthinin, the F1 hybrids contained xanthinin and xanthumin as well as xanthinin‐related compounds and their stereoisomers, xanthumanol, deacetoxylxanthumin, and tomentosin. The Asiatic plants of “strumarium” from Hong Kong involved in the crosses produce approximately equal percentages of xanthinin, xanthatin and xanthinosin, but those from India contain only xanthinosin. The putative introduction of the American morphological complex, “chinense,” contains xanthumin as the major component but shows chemical diversity that indicates genes derived from the indigenous “strumarium” complex.

Environmental Interaction and The Genetics of Flowering

“…However, native Xanthium races in North America shows considerable photoperiod adaptation to latitude (164) and the north ern-most populations require a night length of only 7.5 hr to induce fl owering, while in races from as far south as Mexico or Hawaii the critical night length may be as long as 10.75-11.00 hr (101). In Europe the northern-most strains show a photoperiod response only thinly separated from day neutrality (103) and ONP do occur in the "strumarium" complex from India (105). This variation has received some genetic study (102,103,105) but the bulk of the detailed physiological work has been conducted on a single ecotype, the "Chicago" strain (172).…”

“…In Europe the northern-most strains show a photoperiod response only thinly separated from day neutrality (103) and ONP do occur in the "strumarium" complex from India (105). This variation has received some genetic study (102,103,105) but the bulk of the detailed physiological work has been conducted on a single ecotype, the "Chicago" strain (172). In contrast, the wide ecotypic variation in photoresponse types found in Chenopodium rubrum has been used effectively in physiological studies (32, 85, 189) but we have little informa tion on the genetic basis of the differences in rhythmic flowering responses, critical night length, etc.…”

Response of Xanthium strumarium populations to sublethal applications of bentazone

“…Even when similar environmental conditions are provided, an overall tendency for divergence between plants from natural versus agricultural habitats is evident (Blais & Lechowicz, 1989). Underlying mechanisms controlling interpopulational variation in this species that have been proposed are differences in microhabitats (Blais & Lechowicz, 1989), latitudinal distribution (Ray & Alexander, 1966), hybridization (McMillan et al, 1976) and severity of predation (Hare, 1980).…”