Expanding the boundaries of gene variation for crop improvement

The increased attention on genomics and the use of model species have greatly expanded the ability to detect and create variation. At least 23 plant species either have their genome sequenced or will soon be sequenced. Utilization of the TILLING technology in wheat has allowed the identification of more variation at the waxy locus than had been detected in the previous 25 years. Site-specific mutagenesis via oligonucleotide mismatches or zinc finger nucleases directed toward specific genes allows changes in a directed manner. The use of RNAi allows expression changes leading to useful variation such as root-knot resistance in Arabidopsis, reduction in cotton seed gossypol, cytoplasmic male sterility in tomato and tobacco, and delayed senescence in wheat. We have produced oat plants with individual maize chromosomes by crossing oat x maize followed by embryo rescue. Oat-maize addition lines (OMAs) are now available for all 10 maize chromosomes in various oat genetic backgrounds. OMAs also have been produced with the maize chromosomes coming from different genetic backgrounds (Seneca 60, B73 and Mo17). Monosomic OMAs have been gamma-irradiated to produce Radiation Hybrid (RH) lines with either a diminutive form of the maize chromosome addition or a translocation of a piece of the maize chromosome with an oat chromosome. Approximately 650 RH lines have been produced and defined by 40 markers for that particular chromosome. The OMA and RH lines are useful for many genetic studies, such as mapping individual sequences (polymorphisms are not required), transposable elements, and members of gene families; chromosome isolation, chromosome pairing, centromere isolation, etc. Also of interest is the evaluation of the materials for the introgression of maize characteristics into oat, such as disease resistance and C4 photosynthesis. All of these technologies expand the boundaries for more directed genomic changes enhancing the options for crop improvement. (author)