PCR ANALYSIS OF X-TYPE AND Y-TYPE GENES PRESENT AT THE COMPLEX GLU-A1LOCUS IN DURUM AND BREAD WHEAT

Genes (x-type) corresponding to different high-molecular-weight gluten in subunits encoded at the Glu-A1 locus present in bread- and durum-wh eat cultivars have been selectively amplified by the polymerase chain reaction (PCR). DNA fragments corresponding to an unexpressed x-type g ene were also amplified. As unexpressed y-type genes may or may not co ntain an 8-kb transposonlike insertion, two different sets of primers were designed to obtain amplification of DNA fragments corresponding t o these genes. Amplified DNA fragments were also digested with restric tion enzymes. The digestion patterns of amplified fragments correspond ing to unusual x-type subunits showed similarities with genes encoding the most common subunits 2 and 1. The unexpressed amplified x-type g ene showed a restriction pattern similar to the one obtained with the allelic gene encoding high-molecular-weight glutenin subunit 1; homolo gies were also found within the repetitive region of the linked y-type genes. On the basis of these observations it is postulated that an an cestral active x-type gene, most likely corresponding to subunit 1, wa s silenced following the insertion of the 8-kb transposon-like fragmen t into the linked y-type gene.