Cytogenetics 

Identification of the diploid ancestors of quinoa (Chenopodium quinoa) and its wild tetraploid relatives

Quinoa, a South American broadleaf seed crop, is a tetraploid (4x) derived from ancient hybridization between two unknown diploids. Thus, we would expect that there are at least two copies of every genetic locus. However, one of the 18S-5.8S-25S ribosomal RNA (aka NOR rDNA) loci has been deleted in quinoa. We are comparing the sequence of the variable portion of this locus, the intergenic spacer (IGS), among candidate-ancestor 2x wild diploids with 4x quinoa and 4x Mexican huauzontle (C. berlandieri nuttaliae) in an effort to identify the ancestors of these crop species and to study the evolution of this important genetic locus.

Another approach we are taking is to identify the maternal lineage of quinoa by comparative sequencing of highly variable regions within the chloroplast genome.  This is possible because the chloroplast, which contains its own circular chromosome of DNA, is maternally inherited.  Our research is pointing to a series of North American diploid species as the likely donors of the maternal genome in quinoa's distant ancestry.

Chromosomal genetics and genetic resource conservation/utilization in oat (Avena spp.).

Oat is the fifth or sixth most important cereal grain crop and an important source of soluble dietary fiber, proven in clinical research trials to lower serum cholesterol. Ironically, its very close relative wild oat (A.fatua) is among the most significant weeds of the temperate zone. These 42-chromosome species are descended from a series of 14- and 28-chromosome Mediterranean zone grasses having genes for resistance to oat fungal and viral diseases. In conjunction with researchers at the USDA-Agricultural Research Service, for example, we are working on refining the oat genetic map and in evaluating potentially new resistance genes for crown and stem rust that are found in the 28-chromosome Moroccan oat-weed A. magna/maroccana.  Together with our USDA-ARS partners and collaborators at Alabama A&M University, we are working on developing chromosome-specific DNA markers and sequence libraries through the microdissection and cloning of individual oat chromosomes picked using laser-capture microscopy, or LCM.  My lab is also working on studying inheritance of chromosome rearrangements, especially intergenomic reciprocal translocations, in oat.