DETECTION OF Y-TYPE SUBUNIT AT THE GLU-A1 LOCUS IN SOME SWEDISH BREADWHEAT LINES

Electrophoretic and reversed phase high performance liquid chromatogra phic (RP-HPLC) analyses were performed on gluten proteins extracted fr om flours milled from two different Swedish bread wheat lines; these l ines have been reported to possess a novel high M(r) glutenin subunit controlled by a gene at the Glu-A1 locus, referred to as 21. Although RP-HPLC indicated that subunit 21 has a surface hydrophobocity simil ar to that of the commonly occurring allelic subunits 1 or 2, it diff ers from them in isoelectric point, being more basic when analysed by two dimensional gel electrophoresis (IEF/SDS-PAGE). RP-HPLC separation s of high ill, glutenin subunits showed the presence of an additional peak, tile behaviour of which was similar to that of y-type subunits e ncoded by genes at the Glu-A1y locus and present only in wild wheats T . urartu (AA) or T. dicoccoides (AABB). Based on chromatographic resul ts and on the tight linkage observed with subunit 21, it is suggested that the additional component (indicated as 21y), present in the bre eding Lines analysed, corresponds to the y-type subunit encoded at the Glu-A1 locus. Genes encoding the subunits 21 and 21*y were also anal ysed by polymerase chain reaction (PCR). Contrary to what was observed for the polypeptide itself. the gene corresponding to subunit 21 was similar in size to that encoding subunit 2 and shorter than that cor responding to subunit 1. Moreover, the amplification product correspon ding to tile active 21y gene was shorter than that of the allelic ina ctive gene present in the bread wheat cultivar Cheyenne. As reported f or other high M(r) glutenin subunits, gene size differences observed w ere due to a different length of the repetitive region. Because cultiv ated polyploid wheats have been shown to have only the x-type subunit at the Glu-il? locus, ii is speculated that the new combination, with both x- and y-type subunits expressed, might have been introgressed du ring breeding processes from the wild wheat progenitors T. urartu or T . dicoccoides, which have genotypes expressing both types of subunits. (C) 1996 Academic Press Limited