IDENTIFICATION OF RAPD MARKERS LINKED TO GENETIC-FACTORS CONTROLLING THE MILLING ENERGY REQUIREMENT OF BARLEY

Doubled haploid (DH) populations of barley have been used in combinati on with PCR-based polymorphic-assay procedures to identify molecular m arkers linked to genes controlling the milling energy requirement of t he grain. Milling energy (ME) is a quantitative trait and locating ind ividual quantitative trait loci (QTLs) involved the construction of bu lks by combining DNA from DH families representing the extreme members of the distribution for ME. In addition, the individuals had alternat ive alleles at the Rrn2 locus that has previously been shown to be lin ked to an ME QTL. The DNA bulks were screened with Randomly Amplified Polymorphic DNA (RAPD) markers and polymorphic amplification products tested for linkage to genes influencing the expression of ME in a DH p opulation. Several markers were identified which are linked to a QTL c ontrolling ME and the recombination fraction determined by maximum lik elihood procedures. The results indicate that DHs in combination with RAPDs and bulked segregant analysis provide an efficient method for lo cating QTLs in barely. Furthermore, this approach is applicable to map ping other QTLs in a range of organisms from which DH or recombinant i nbred lines can be extracted.