| Barley is the fourth food crop in China and plays a very important role in the development of economy. To meet further social and people's living standards, new barley varieties will require high yields, better quality, high resistance and wide adaptability. Genetic characterization of barley germplasm will be crucial for the development of new barley varieties.Dwarfism is a valuable trait in crop breeding, successful use of a dwarfing gene or dwarf source is critical for developing dwarf cultivars. In barley, more than 30 types of dwarfs or semidwarfs have been found. However, only a few of them have successfully been used in barley breeding program. Dwarf source and dwarf genes are unitary in barley breeding, not only limited further increases in yield and quality, but also narrowed the genetic basis, reduced biodiversity and increased vulnerability of disease and pest for new varieties. Therefore, discovery of new dwarf genes or dwarf sources is important for barley breeding. New dwarf source "huaai 11" has early maturity and good general combining ability. Utilization of this dwarf resource can broaden the genetic basis of barley dwarf breeding. We mapped dwarfing gene btwdl in Huaai 11 using a doubled-haploid (DH) population from a cross between Huaai 11 and Huadamai 6. In order to efficiently use this excellent germplasm for breeding program, we also analyzed the QTL underlying agronomic traits and quality traits in this line.Heading date is a major determinant of the regional and seasonal adaptation of barley varieties. Appropriate heading date is an important goal of barley breeding. The dogma is that introduced germplasm is more likely to be adapted if it come from a similar latitude. However, barley germplasm introduced from similar latitudes of South-East Asia are extremely early heading in the Australian environments and vice versa. Therefore, we mapped heading date genes using Galleon×Haruna Nijo DH population and Baudin×AC Metcalfe DH population. The results will help us understand the main reason causing heading date difference in two similar latitude locations, Australia and China, The results of these researches are sumarized as follows:1. Inheritance of the dwarf gene btwdl:dwarf Huaai 11 was crossed with nine tall varieties. All the F1 plants were tall. Both the tall and dwarf plants appeared in all the F2 populations with a 3:1 segregation ratio. The x2 testshowed the segregation is not significantly different from the expected 3:1 ratio, indicating that the dwarf trait is controlled by single recessive gene in the Huaai 11. This gene is designated as btwdl.2. Allelic relationship between btwdl and other dwarfing genes:The F1 of Huaai 11 x Monker was crossed with other four dwarf varieties. All progeny in the four crosses are tall, suggesting that the gene btwdl controlling plant height in the Huaai 11 is nonallelic with br, uzu, sdwl and denso genes in these four dwarf varieties.3. Mapping of the dwarf gene btwdl:SSR marker and BSA analysis were used to map the dwarfing gene in the Huaaill. Linkage analysis found that four SSR markers from chromosome 7H (BmacO31, Bmacl67, Bmag217 and Bmag900) were linked with the target gene btwd1. The dwarfing gene btwdl is close to the Bmac031 with a genetic distance of 2.2 cM, which is close to the centromere of 7HL.4. QTL analysis of the agronomic and quality traits:This study using Huaai 11×Huadamai 6 DH population as research materials, Quality trait grain protein content and eleven gronomic traits such as heading date, spike numbers per plant, main spike length, spikelet number of main spike, spikelet number per plant, grain number per plant, grain number per spike, grain weight per plant, grain weight per spike,1000 grain weight, number of tillers were investigated. Sixty three pairs of SSR primers showed polymorphic between the two parents, and were used to construct a genetic linkage map. Composite interval mapping (CIM) analysis of 12 traits identifiedt a total of 47 QTL,29 of them were new QTL.5. Mapping of heading date gene in barley:The Galleon x Haruna Nijo DH population was used to map heading date gene at two location China (Wuhan,30°33'N) and Australia (Perth,31°56' S) with three different treatments including normal autumn sowing, late sowing and pot experiment with 18h photoperiod. QTL analysis detected one major QTL (Qtl-5H) in China, which was located on chromosome 5H, and explained 33%-50% of the phenotypic variation. In Australia, two major QTL (Qtl-4H and Qtl5H) were detected for heading dates on chromosomes 4H and 5H and Qtl-4H and Qtl5H interaction. The Qtl-4H/Qtl-5H interaction explained 13%-36% of phenotypic variation. The Qtl-4H/Qtl-5H interaction may be main reason that DH lines are earlier heading in Australia than China.6. Mapping of long photoperiod gene in barley:Bandin×AC Metcalfe DH population was used. In China (Wuhan,30°33'N), three different treatments including normal autumn sowing, late sowing and pot experiment with 18h photoperiod were conducted. In Australia (Perth,31°56' S), two different treatments including normal autumn sowing and pot experiment with 18h photoperiod were performed. QTL analysis detected a major QTL for photoperiod response and mapped onto the long arm of chromosome 4H in both Australian and Chinese locations. The QTL was flanked by the markers Xp12m50A199-Xp13m47B399 and accounted for 77.5% and 37.8% of phenotypic variation in Australia and China, respectively. Two QTL underlying heading date detected in this mapping population.
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