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Weed Status
Members of the Chenopodium species have been implicated among the greatest weed threats to agriculture in North America and globally. This success can be attributed to their ability to survive across a range of environmental conditions due to their high reproductive capacity, variation in their dormancy and germination requirements, and abiotic stress tolerance.

In addition, the larger Amaranthaceae family is one of five weed families (along with Poaceae, Asteraceae, Brassicaceae, and Chenopodiaceae) that represent only 50% of the world’s principal weeds but account for about 70% of all cases of herbicide resistance. Most research identifies European species C. album as a prime candidate for evolving resistance to multiple herbicides, in particular to triazines and glyphosates. The weed status and herbicide tolerance of C. berlandieri is less researched and less clear due to its many wild and semi-domesticated forms resulting from frequent hybridization and polyploidy.

The spread and sporadic domestication of C. berlandieri across eastern North America and Central America has resulted in a complex network of domesticated and wild sub-species known to co-exist and interact in shared ecosystems. Historical evidence has been identified to support this interaction, namely human paleofeces collected from Salts Cave in Kentucky and Big Bone Cave in Tennessee found to contain both seeds from weed and crop forms of the plant seemingly consumed within hours of each other, suggesting close spatial proximity and a potential for hybridization between populations.

Morphological studies identified that seeds from weedy varieties of C. berlandieri tend to have a thicker testa (seed coat), a more rounded or biconvex margin configuration, more prominent testa patterning, a less developed beak, and a smaller overall size when compared to their domesticated counterparts. However, intermediate morphologies were also identified, indicating genetic interaction (crossing over) between these groups.

This cross-compatibility and hybridization leads to the formation of crop-weed complexes, within C. berlandieri as well as with other members of the Chenopodium species. For example, following the spread of C. quinoa across North America as a novel crop, one study found that up to 30% of wild C. berlandieri grown along the periphery of quinoa fields were crop/weed hybrids. Gene flow was observed to be asymmetric (from crop to weed), due to a preferential flow of pollen from high-density populations of domesticated C. quinoa to dispersed populations of wild C. berlandieri. This directional crop-weed interaction has implications for the future of introgressive change in wild C. berlandieri varieties. While genetic introgression is often degenerative for both crops and wild plants , it may also promote greater biodiversity in conventional cropping systems and present research opportunities for new crop varieties.