Artificial Hybridization Among Species of Chenopodium sect. Chenopodium

The taxonomic significance of those morphological characters that have been used to delimit Chenopodium sect. Chenopodium subsect. Cellulata has been questioned. Species of this alveolate-fruited group are therefore often not treated in regional manuals, especially those covering the eastern United States. Alveolate- fruited species usually are included with the synonymy of C. album s. lat. of subsect. Leiosperma. The validity of subsect. Cellulata was tested through two programs of artificial hybridization. Results support the circumscription of subsect. Cellulata as a unit distinct from other elements of sect. Chenopodium. Hybridization between taxa within subsect. Cellulata produced viable F1 plants, whereas intersubsectional crosses resulted in inviable hybrids or none at all. Chenopodium bushianum, an alveolate- fruited species of northeastern North America that is often confused with C. album, showed complete genomic compatibility with C. berlandieri subsp. berlandieri, a com- mon alveolate-fruited weed of western North America. This, plus the presence of apparent intergrading populations in the area of sympatry, indicates that the two might be better treated as a single species. When morphological, cytological, and hybridization data are considered, all taxa of the Cellulata complex appear to con- stitute a relatively coherent group that is well removed from C. album and related species of subsect. Leiosperma. Hybridization data also indicate the presence of a restorer for cytoplasmically inherited male-sterility in C. quinoa. This factor appears to be present in some strains of C. quinoa subsp. quinoa and some strains of C. berlandieri subsp. berlandieri.