Plant & Animal Genome VI Conference

W49

QTL MAPPING OF SUGAR CONTENT (AND OTHER TRAITS) IN SUGARCANE: TOWARD STED SELECTION, AND MOLECULAR CLONING IN COMPLEX GENOMES

1. Department of Soil and Crop Science, Texas A&M University, College Station, TX 77843-2474
2. Texas A&M Agricultural Experiment Station, Department of Soil and Crop Sciences, 2415 East Hwy. 83, Weslaco, TX 78596

Using a detailed comparative map of sugarcane and it small-genome relative sorghum, we have performed molecular dissection of genes associated with both agronomic and economic traits in sugarcane. We will report on the second step ("verification") of the two-step QTL mapping algorithm we previously proposed for the large genome of sugarcane. Many tentative QTLs suggested in the first step of the process were indeed verified by re-investigation in larger populations, and we can now offer DNA probes that are diagnostic of a high portion of the total genetic variation in the two sugarcane crosses studied. Correspondence in the location of some QTLs between some or all of the four different parental types, of two different species, suggests that at least some of these DNA probes are likely to be diagnostic of the same traits in other sexual sugarcane populations. The high level of QTL polymorphism within individual elite sugarcane genotypes suggests that ample opportunity remains to improve sugar yields through DNA marker-assisted selection. An experiment to test this hypothesis will be described. As has been reported in several other taxa, we find occasional favorable alleles even in parents whose phenotype was unfavorable, conferring new opportunities to improve elite genotypes. Ongoing work to assemble a detailed set of ESTs well-distributed across the genome, and to merge genetic and physical maps of complex genome plants will be briefly discussed.