The Molecular Markers For Waxy Genes Of Wheat And Their Applications

Waxy genes control amylase synthesis. This study was conducted to develop molecular markers for low amylose content wheat breeding.Based on the known sequences of waxy genes, six PCR-based markers, MAG264 and MAG265, MAG266 and MAG267, and MAG269 and MAG270, specific for loci Wx-Al, Wx-B1 and Wx-D1, respectively, were developed. Marker MAG264, inherited in a co- . dominant manner, can distinguish all three genotypes of the Wx-Al locus from each other. With dominant marker MAG265, Wx-Alb allele can be detected through direct PCR product staining. With an intra control, Wx-Blb allele can be detected using MAG266 and MAG267. The primers of marker MAG269 amplified a 1400bp band in the wild type of the Wx-Dl locus, and a800bpbandinthemutantallele.Howeverintheheterozygousgenotypes, only the Wx-D1b allele was amplified, which made the should-be co-dominant marker MAG269 appeared like a dominant one. It is concluded that the large deletion in the 3'end of the Wx-Dlb allele may affect the PCR amplification of the Wx-Dla allele in the heterozygote genotypes. An extra band appeared in the heterozygote genotypes using the co-dominant marker MAG270, which can be eliminated through 65 C incubation before electrophoresis. Having good repeatability, these PCR-based markers are useful for identifying wheat cultivars with mutant alleles of waxy genes.Using these markers eleven plants with all three null alleles of the waxy loci were selected from the F2 plants derived from 21253 x Yangmai 158. In addition, twenty-nine plants with Wx-AlaWx-Alb alleles, and twenty-seven plants with Wx-DlaWx-Dlb alleles were selected from the BC1F1 plants derived from 21253 x Yangmai 10.A novel band was detected using Marker MAG265 in cultivar Baihuo, which have the normal Wx-Al subunit. Sequence comparison showed that the penta-oligo ATTCG in the first exon were mutated to TGGGA, which led to the amino acid change of FD to GN, subsequenly led to a new -turn in the secondary structure of the encoded product. Thus,this new variation of the Wx-Al locus is designated as Wx-Alf.Forty-six varieties were examined with marker MAG265, sixteen of which, including Nanda 2419, Tutoumai, Fengchan 3, Taishan 1, Baitutoujia, Waitoubai, Tuhulutou, Baiyuhua, Bima 1, Alondra's', Compton, Pato, Mianyang 11, Nandazaoshu 1, Annong92484W and Wannian 1, were amplified with the band pattern same as that of Baihuo.