Validation of molecular markers for covered smut resistance and marker-assisted introgression of loose and covered smut resistance into hulless barley

Inheritance of covered smut resistance was investigated in three hulless x hulled barley populations (CDC Candle/Q21861, CDC McGwire/Q21861, and CDC McGwire/TR640). Greenhouse and/or field screening indicated resistance was controlled by a single major gene from Q21861 and TR640. Three molecular markers (UhR 450, aHor 2 and OPO6(780)) linked to the covered smut resistance gene (Ruhq) in the hulled line Q21861 were assessed for their usefulness in selecting resistant hulless barley. All markers were linked to covered smut resistance in the three populations evaluated, although aHor 2 was only polymorphic in CDC Candle/Q21861. Two strategies, doubled haploidy (DH) and marker-assisted backcrossing (MAB), were used to simultaneously introgress Ruhq and loose smut resistance (Run8) into the hulless barley cultivar CDC McGwire. Thirty-five DH lines were developed from a cross of hulless loose smut resistant line SH00752 (CDC McGwire/TR251) by hulless covered smut resistant line SH01470 (CDC McGwire/Q21861). By screening the 35 DH lines for each of the markers, 14 were identified as positive for both. Following three rounds of screening by artificial inoculation, 12 of those were identified as resistant to both diseases. In the MAB program, "blind'' selection based solely on markers was conducted through the BC3F2 generation; lines resistant to both diseases were obtained. One line, designated HB390, is being advanced to 2nd year of the Western Canadian Hulless Barley Co-operative yield trials, the final step to release of a cultivar for commercial production in Canada. These results confirm that molecular markers can be used in either DH or MAB programs to assist in the rapid introgression of simply inherited disease resistance genes into elite lines, with considerable time and cost savings.