| Wheat is one of the important food crops in the world. With the development of molecular biology, improvement of yield and quality by using biotechnology has been one of the main research fields in wheat. In search of molecular markers closely linked with yield and quality traits is of significance to implement marker aided selection and to accelerate breeding process. Thus, two aspects of research were carried out in this project. One was the identification of QTL for yield and quality traits based on two genetic populations of RIL and CIL(BC2F8) constructed by use of three Australian wheats, 22397, Lang and Bellaroi. The other one was to clone two alleles of Zds gene located in chromosome 2DL and to develop functional marker of yellow pigment content. The main results are as follows:1) There were relatively significant differences in yield and quality traits of two parents, Lang and 22397, of RIL population, although their performance of traits was basically consistent among two environments. The male parent 22397 was better than the female parent Lang in spike length, spikelet number, grain protein content and wet gluten content. The quality traits of RIL lines were markedly superior to those of currently used cultivars of China, and the significant differences and normal distribution were found for the traits of RIL lines. Identification of the CIL population, BC2F8, from Bellaroi and 22397 in two-year-and-location environments showed a consistent trend for diversification of all traits tested. 22997, the male parent, was much better than the female parent Bellaroi in grain protein content, wet gluten content and sedimentation value. Some yield and quality characters were improved in CIL population compared to receptor Bellaroi after two cycles of backcross.2) The correlation analysis indicated that the relations between yield and quality traits were comparatively consistent among environments and two genetic populations, RIL and CIL. Rather complicated relations existed between these traits, as well as between yield traits and quality characters. There were positive or significantly positive relationships between plant height and spike length, spikelet number, thousand grain weight and swelling power, and between grain number per spike and spikelet number. Grain number per spike was negatively related to grain protein and wet gluten content which were of positive relation. Sedimentation value was significantly and positively related to wet gluten content, water absorption, development time, stability time and breakdown time of dough, and significantly negatively related to degree of softening and tolerance index. Swelling power was negative relationship with water absorption and that was significantly positive with fall number. The development time, stability time, breakdown time and evaluation value were significantly positive between each other, whereas they were significantly negative with tolerance index and softening degree.3) Twenty-one QTL were detected for plant height, spike length, thousand grain weight, grain protein content, wet gluten content, grain hardness, test weight, sedimentation value, swelling power, water absorption, stability time, band width, breakdown time and evaluation value in RIL population. They were located in chromosome 1B, 1D, 2A, 2B, 3D, 4B, 5A, 7A and 7B, respectively, with more QTL in 1B and 4B than in others and 5.88~26.9% of phenotype variance explanation for each QTL. Also, GWM0126-WPT-1903 locus in 5A was linked to spike length and contributed 27.98% phenotype variance, and the gene with increased effect from male parent. The fact that a chromosome locus linked simultaneously to some traits and that the different loci in a chromosome linked to the same trait suggested one gene with multi-effect and multi-gene with one effect. Besides, epistatic effects of 12 QTL pairs were detected for spike length, spikelet number, grain number per spike and grain protein content, test weight , swelling power, grain hardness, water absorption, band width, breakdown time and evaluation value. They were non-significantly interacted with environment.4) Forty QTL were identified for yield and quality traits in CIL population tested in two-year-and-three-location environments. They included five QTL for plant height with -3.976~2.838 additive effect (AE) and 7.78~19.14% contribution ratio (CR), four for spike length with -0.328~0.688 AE and 8.02~13.50% CR, one for spikelet number with 10.72% CR, three for grain number per spike with highest CR of 17.10%, four for thousand grain weight with highest CR of 15.54%, two for sedimentation value with 11.18% and 11.99% CR, two for falling number with the highest CR of 11.45%, 12 for wet gluten with 7.74~17.68% CR and four, two and one for test weight, hardness and grain protein content, respectively. Twelve chromosomes were dealt with all the QTL, i.e. 1A, 1B, 2A, 2B, 3A, 3B, 4A, 4B, 5A, 6A, 7A and 7B. Some QTL were located on the same chromosome as those detected in RIL. In addition, 78 pairs of interactions were found in BC2F8 population, 15 between major QTL, 63 between major and non-major QTL. The interactions between major QTL included two for plant height, one for thousand grain weight, one for sedimentation value, 10 for wet gluten and one for test weight, respectively.5) The TaZds-D1, a gene of wheatζ-carotene desaturase (Zds), in chromosome 2DL was cloned with a full length DNA of 6512 bp including 13 introns and 14 exons. An ORF of 1707 bp codes 568 amino acids with molecular weight of 62.5kD. cDNA of the cloned gene showed homology of 80.9%, 81.4%, 80.5%, 64.9%, 68.8% and 67.7% with that of rice, sorghum, maize, Arabidopsis, grapevine and Trichocarpa, respectively.6) A functional marker, YP2D-1, was developed based on the difference of two alleles, TaZds-D1a and TaZds-D1b, of TaZds-D1 in chromosome 2DL. Validation was done of the functional marker through QTL linkage analysis with the yellow pigment content, DH population test and determination of as many as 300 cultivars or lines of wheat. It was found that this functional marker was closely related to wheat yellow pigment content with 18.4% of phenotype contribution ratio, and could be of availability in breeding selection. |
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