Identifying DNA Sequence Variation in Key N-Metabolism Genes in Different Species of Chenopodium

Research has shown that the domesticated form of goosefoot known as quinoa (Chenopidum quinoa, 2n = 4x = 36, AABB genomes) includes genotypes that are capable of maximizing N uptake when low levels of this mineral nutrient are present.   These cultivars, from the Andean highlands, present a logarithmic growth pattern in response to increasing N; they respond well at low N levels but exhibit decreased benefit above a certain soil N threshold.  This is a critical physiological characteristic of quinoa, considering that the vast majority of quinoa is produced either by impoverished Andean subsistence farmers or by native farmer co-ops on high-altitude volcanic, low-N, low organic matter soils.  Other, mainly lowland, quinoa varieties are N-inefficient, responding positively at a linear rate with increasing N-fertilization.  Genomic Sanger sequences of cytosolic GLN 1 (glutamine synthetase), NAR (nitrate reductase) and NIR (nitrite reductase) genes were obtained from twelve wild and domesticated genotypes of Chenopodium. These samples were representative of Eurasian and North and South American species and varieties of goosefoot. Inclusion of samples from both the Old and New Worlds was critical because quinoa’s A and B genomes showed homology to diploids from the New and Old Worlds, respectively.  Cultivars included both N-efficient and N-inefficient types.  Sequences were analyzed and identified unique locus- (allelic) and subgenome-specific (orthologous) variants.