LINKED MORPHOLOGICAL AND MOLECULAR MARKERS ASSOCIATED WITH COMMON ROOT-ROT REACTION IN BARLEY

Selection of common root rot [Cochliobolus sativus, (Ito & Kurib.) Dre chsl. ex Dastur] resistant barley germplasm is difficult due to the in fluence of environment on disease expression and the quantitative natu re of resistance. Morphological and molecular markers associated with common root rot resistance could be used to increase the efficiency of selection of resistant germplasm and facilitate transfer to desirable barley genotypes. Forty-five morphological marker sets consisting of four to six backcross-derived lines for each marker in a common backgr ound (cultivar Bowman) were planted in disease nurseries at two locati ons in each of 3 yr. Disease reactions of the backcross-derived lines were tested for a difference from the disease reaction of Bowman, whic h indicated a putative association between the marker and common root rot reaction. An association was obtained between common root rot reac tion and one set of backcross-derived lines that contained two linked markers: glossy-sheath (gs4) and orange lemma (o). A RAPD marker close ly linked to gs4 and o was also associated with common root rot reacti on. The RAPD marker was associated with the allele for resistance, whi le gs4 and o were associated with the allele for susceptibility. The R APD marker would be most useful in the selection of common root rot re sistant germplasm and the transfer of this resistance to other genotyp es.