H. X brevifolius E.E. Wats.
H. X divariserratus R.W. Long
H. X doronicoides Lam.
H. X glaucus Small
H. X intermedius R.W. Long
H. X kellermanii Britt.
H. X laetiflorus Pers.
H. X multiflorus L.
H. X orgyaloides Cockerell
H. X verticillatus E.E. Wats.
H. divaricatus X H. giganteus H. grosseserratus X H. mollis H. mollis X H. occidentalis H. divaricatus X H. grosseserratus H. giganteus X H. mollis H. divaricatus X H. microcephalus H. grosseserratus X H. maximiliani H. grosseserratus X H. salicifolius H. pauciflorus X H. tuberosus H. giganteus X H. grosseserratus H. annuus X H. decapetalus H. maximiliani X H. salicifolius H. angustifolius X H. grosseserratus
Source: Adapted from USDA, Plant Names, http://plants.usda.gov/, 2006.
The following is a key to sections of Helianthus (after Schilling and Heiser, 1981):
1. Perennial (except H. porteri (A. Gray) Heiser); disk corollas and style branches usually yellow, where disk corollas red or purple; leaves usually all opposite 2
2. Plants from taproots of long creeping roots; plants less than 1 m tall; basal rosette of leaves lacking or poorly developed; western U.S. and Mexico I. Ciliares
2. Plants from rhizomes, tubers, or crown buds (except H. porteri); plants greater than 1 m tall, or if less, having a basal rosette of leaves; mostly eastern and central U.S II. Atrorubens
3. Annuals; disk corollas red, style branches yellow, stems glabrous and glaucous III. Agrestes
3. Annuals; disk corollas and style branches usually red or purple; leaves mostly alternate IV. Helianthus
Jerusalem artichoke is quite variable in morphology (see Chapter 4), but can be separated fairly easily from other species of Helianthus with the exception of H. strumosus L., a closely related species that also forms tubers. Of the two species, H. tuberosus typically has a more dense pubescence, more alternate leaves, greater leaf serration, broader and more decurrent leaves, a greater pubescence on the under surface of the leaves, darker bracts, and longer ray petals than H. strumosus (Rogers et al., 1982). H. strumosus (paleleaf woodland sunflower) occurs throughout the eastern U.S. (USDA, 2006). H. tuberosus is found throughout the U.S., and wild populations are found especially in the open in moist soil along streams, ditches, and roadsides.
The advent of molecular genetic techniques such as amplified fragment length polymorphism (AFLP) analysis, where the degree of difference in the DNA between individual lines or species can be compared, has allowed the establishing of a much more precise assessment of genetic relatedness.
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