Cotton breeding researchers take giant leap
Narrow germplasm base and limited technology have made it difficult for cotton researchers to identify specific DNA markers needed to locate genes that confer desirable traits. But that's no longer the case.
David Stelly, Ph.D., a Texas A&M AgriLife Research cotton breeder in College Station, said cotton is ready to merge into the breeding fast lane with the expected release of "cotton SNP chips" loaded with single nucleotide polymorphisms, or SNPs (snips). SNPs are variations within the DNA.
"The new chip will be the first of several quantum steps forward over the next couple of years that will open many doors for cotton breeding research and improvements," Stelly said. "While DNA markers are not a panacea in themselves, they can turbo-charge the breeding process."
Joining Stelly and Amanda Hulse, his Texas A&M University doctoral student, and Dr. Fei Wang, his post-doctoral researcher, on this massive project were researchers from the University of California-Davis, Brigham Young University and the U.S. Department of Agriculture-Agricultural Research Service, all with support from Cotton Incorporated.
Markers differentiating cotton lines are essential to applying genomic technologies in breeding research, he said. For maximum utility, the DNA markers must be numerous, variable among breeding lines and relatively cheap to screen and use. Across all crops, SNPs are the most numerous, widely distributed type of DNA marker. They also are the least expensive to use for most purposes.
"Breeders of cotton and other crops traditionally create genetic advances by hybridizing, inbreeding and selecting," Stelly said. "We hybridize lines with prospectively complementary genetic differences and sift through subsequently inbred generations to find genetically recombined lines with attributes superior to both parents."
A new breeding product must be equal to or better than all other available cultivars to compete well in the marketplace, he said. To enhance the odds of finding excellent genetic recombinants, breeders almost always rely on parents that are themselves elite and, as a result, closely related.
Even so, the breeder's selection process must be comprehensive, Stelly said. Lines must be tested in diverse growing environments and address all important traits, involving multiple genes, many of which are expensive to evaluate. Some processes can be significantly aided by molecular markers, including parental selection, dissection of genetically complex traits and selection for beneficial genes and regions.
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