Chenopodium

The genus Chenopodium L. has a worldwide distribution and includes species that were domesticated on four continents. Several species are notorious as invasive weeds, having spread far beyond their centers of origin. Among the wild species are some that are common and others that are restricted to niche environments, appearing ephemerally in response to episodically favorable climatic conditions. Chenopodium inhabits niches that include some of the harshest environments on earth for plant survival. The ability of Chenopodium species to survive in saline littoral and saltpan environments, high-ultraviolet montane plains and valleys (Andes, Himalayas), and barren deserts (Atacama, Australia) suggests that this genus possesses unusually potent and diverse plant stress-response mechanisms. The domesticated species are becoming increasingly valued for the balanced content of dietary essential amino acids in their seed proteins and for the rich mineral and vitamin content of their foliage. The genus has been recalcitrant to thorough systematic and phylogenetic study due to phenotypic plasticity in several major species (most notably C. album), confused taxonomy in closely related genera (especially Atriplex and Dysphania), as well as the sporadic and unpredictable appearance of a number of key annuals. Genetically, the genus has a base chromosome number of x = 9 with numerous polyploids up to the level of hexaploidy. We herein review the wild Chenopodium species, with special emphasis on those of the Americas that should be most closely related to Andean quinoa (C. quinoa) and its domesticated cousins from Mexico (C. berlandieri nuttaliae); a small number of studies on interspecies crossability; and potential characteristics of interest in the wild species for improving the domesticated quinoas.