Molecular Detection Of Dwarfing Genes In Chinese Bread Wheat

Totally 432 cultivars and advanced lines from major Chinese wheat regions and 70 DHlines of Zhongyou 9507 and CA 9632 with significant difference in plant height weredetected by two STS markers and one microsatellite WMS 261 for the semi-dwarfing genesRht-D1b and Rht8. The distribution frequencies of the dwarfing genes were determined andthe utilization of the three markers in the validation and effects of dwarfing genes on theplant height in bread wheat (Triticum aestivum L.) were tested. The results were summarizedbelow:1. Frequency of Rht-D1b Two PCR-based STS markers could be used to test the presence of Rht-D1b in wheatgenotypes.The distribution frequency of Rht-D1b gene in Northern Winter Wheat Zone,Yellow & Huai River Facultative Winter Wheat Zone, Middle & Low Yangtze Valley WinterWheat Zone, Southwestern Winter Wheat Zone, Northern Spring Wheat Zone, NorthwesternSpring Wheat Zone, Northwestern Spring Wheat Zone and Xinjiang Winter-Spring WheatZone was 47.5%., 40.9%, 58.7%, 36.8%, 42.5%, 50.0%, 22.2%, 13.3% and 22.2%,respectively.2. Frequency of Rht8 gene A wheat microsatellite marker, WMS 261, whose 192bp allele closely linked to thedwarfing gene Rht8 on chromosome 2DS, was used to screen 432 wheat genotypes and 70DH lines from Zhongyou 9507 and CA 9632 to access the variation at this locus. Onaverage,the frequency of Rht8 specific to WMS261 marker in China was 45.1%. The highestfrequency of Rht8 was found in Yellow & Huai River Facultative Winter Wheat Zone with57.7% ,followed by Southwestern Winter Wheat Zone with 52.9%. The frequency of Rht8gene in Northern winter wheat and Yangtze Valley was 34.9% and 15.8%, respectively. InNorthern Spring Wheat Zone, Northwestern Spring Wheat Zone, Northeastern Spring WheatZone and Xinjiang Winter Spring Wheat Zone, the frequency of Rht8 gene was 25.0%, i11.1% , 6.7% and 22.2%, respectively.3.Validation of PCR marker The results of molecular detection of 432 genotypes indicated that 3 molecular markerscould be used to detect the semi-dwarfing genes Rht-D1b and Rht8. The primer 3 couldamplify one diagnostic band of 264bp in the wild type gene Rht-D1a, the primer 4 for onediagnostic band of 254bp in mutant type gene Rht-D1b, and the primer 5 could amplify 4different diagnostic bands of 165bp, 174bp, 192bp and 202bp for the detection of Rht8. Theresults were identical to the ones of pedigree analyses, and the same for the gene Rht-D1b.Therefore, if the pedigree of a wheat cultivar was clear, the two STS markers and WMS261could be applied to examine and screen genotypes for semi-dwarfing genes Rht-D1b andRht8 in wheat breeding programmes.4. Effects of dwarfing genes and QTLs on plant height Rht8 was a weak reducing plant height by about 6.0cm and Rht-D1b was a middlereduing height gene by about 10.0 cm. A significant difference at 1% level was found in plantheight, spike kernel number and thousand grain weight under different environments,whereas the difference in plant height between Zhongyou 9507 and the genotypes of Rht8 orRht-D1b+Rht8 was not significant with a range of 88.6—97.5cm under the same growingcondition, while a significant difference was detcted between Zhongyou 9507 and CA 9632or the genotype of Rht-D1b whose plant heights were 77.4cm and 88.6cm. Three major QTLswere located on chromosomes of 2DS, 4DS and 6BS, repectively and two major QTLscorresponding to dwarfing genes Rht8 and Rht-D1b derived from CA 9632 showed positiveeffect on plant height, one major QTL from Zhongyou 9507 with negetive effect on plantheight.