A MONOCLONAL-ANTIBODY CHROMOSOME MARKER ANALYSIS USED TO LOCATE A LOOSE SMUT RESISTANCE GENE IN WHEAT CHROMOSOME 6A

Many genes have been located in wheat chromosomes, yet little is known about the location of genes introduction for resistance to Ustilago t ritici, which causes loose smut. Crosses were made between the loose s mut susceptible alien substitution lines Cadet 6Ag(6A) and Rescue 6Ag( 6A) (lines in which Agropyron chromosome 6 is substituted by wheat chr omosome 6A) and four cultivars resistant to U. tririci race T19: 'Cade t', 'Kota', 'Thatcher' and 'TD18'. The segregating progeny were tested for reaction to race T19 and for the level of binding with a monoclon al antibody specific to a chromosome GA-coded seed protein. The antibo dy, which does not bind to seed protein extracts in the absence of the 6A chromosome, was used as a chromosome marker. An association was es tablished between resistance to race T19 and the presence of chromosom e 6A for each of the cultivars tested, indicating that resistance to r ace T19 resides in chromosome 6A. Ustilago tritici race T19 resistance in 'Cadet' appears to be located in the short arm of chromosome 6A, b ased on the evaluation of the Cadet 6A long ditelosomic stock, which w as susceptible, and the Cadet 6A-short: 6-Agropyron-short alien transl ocation stock, which was resistant.