The American geneticist, E. R. Sears, was the founder of wheat chromosome engineering.He established the monosomic series of common wheat, which greatly facilitated cytogenetic analysis of wheat. However, problems of ...The American geneticist, E. R. Sears, was the founder of wheat chromosome engineering.He established the monosomic series of common wheat, which greatly facilitated cytogenetic analysis of wheat. However, problems of univalent shift and labor involved in chromosome counting have limited the common usage of these materials. To circumvent these problems, I developed an alternative set of monosomic lines, in which the presence of the univalent chromosome was indicated by the production of blue pigmentation in the aleurone tissue of seeds. The gene(s) responsible for the blue pigmentation were carried on a short chromosomal fragment of Agropyron elongatum. This chromosomal fragment has been transferred to the different chromosomes of common wheat using radiation induced translocation. On the spike derived from a blue grained monosomic wheat (2 n =41, the univalent chromosome carries the gene for the blue pigmentation), four types of seeds are produced. The deep blue seed has 42 chromosomes, the medium blue and light blue seed has 41 chromosomes, and the white seed has 40 chromosomes. The monosomic genotype is easily identified based on the color of the seed, without the use of microscope. So far, blue grained monosomic lines have peoduced 11 of the 21 different wheat chromosomes. In the course of propagating the blue grained monosomics, I found that the fertility of the nullisomic lines (2 n =40, represented by white seeds) could be improved by continued selfing and reselection. Using the resulted self fertile nullisomic lines, I established an efficient procedure for producing alien substitution lines of wheat. The utilization of the blue grained monosomic lines and the self fertile nullisomic lines may facilitate chromosome engineering studies in wheat.展开更多
Seed protein content, nutritional balance and processing property of flour are the three major aspects of wheat protein quality. Most Chinese wheat cultivars are comparable to their Western counterparts in terms of se...Seed protein content, nutritional balance and processing property of flour are the three major aspects of wheat protein quality. Most Chinese wheat cultivars are comparable to their Western counterparts in terms of seed protein content and nutritional balance. However, relatively few of them possess good processing property. The main reason underlying the poor processing property of hexaploid Chinese wheat varieties is the weakness in gluten strength. Considering that wheat gluten is mainly composed of a mixture of a finite number of storage protein species and that the storage protein species may determine gluten strength through combinatorial controls, we formed the following strategies in our studies on understanding and manipulating the genetic basis of protein quality in Chinese wheat. 1. Genetic analysis. By performing well structured genetic analysis, we hope to identify two types of storage protein genes, those genes whose presence is associated with good processing property (the desirable genes, or the D type genes) and those whose presence is always associated with undesirable processing property (the undesirable genes, or the U type genes). Two sets of genetic analysis are being conducted currently. The aim of the first set of analysis is to obtain nonfunctional mutants for the majority of the genes whose products are present in the gluten. This analysis is expected to yield information on the function of individual members of storage proteins, some of which may be encoded by the D type genes, in gluten strength control. The aim of the second set of analysis is to identify potential genetic factors that may be responsible for causing weakness in gluten strength in Chinese wheat through the use of recombinant inbreed lines. This analysis may produce information on the function of the storage proteins specified by the U type genes. 2. Molecular analysis. On the basis of above genetic analysis, a molecular approach will be undertaken to clone the D and U type genes. The cloned genes will be characterized in terms of genetic diversity in cultivated wheat and wild species related to wheat and potential application in molecular breeding for processing property improvement. Because of the known association between the HMW glutenin subunit 1D×5 and good processing quality, we are now searching wheat related wild species for better versions of the 1D×5 subunit and testing their potential in wheat processing quality improvement. 3. Molecular breeding. The above genetic and molecular analysis should result in sufficient gene and marker resources suitable for wheat processing quality improvement through molecular breeding. The D type genes will be transferred into high yielding, hexaploid wheat varieties using the transgenic technology. The molecular markers linked to the U type of genes will be used to screen breeding materials for an early avoidance of this type of genes in breeding programs. In summary, the combination of theoretical and applied investigations described above should contribute to wheat protein quality improvement in both China and abroad. In the future, wheat quality breeding will be a more productive and efficient enterprise worldwide.展开更多
Deficiency of available phosphorus in alkaline soil is a serious problem in northern China. This contrasts with the finding that the total amount of phosphorus in the soil is, actually, very high (over 200 times of it...Deficiency of available phosphorus in alkaline soil is a serious problem in northern China. This contrasts with the finding that the total amount of phosphorus in the soil is, actually, very high (over 200 times of its available form). Starting from 1990, my colleagues and I initiated a new research project with a longer term aim to breed phosphorus efficient wheat varieties. From among 500 wheat lines, several genotypes that could tolerate low phosphorus level in the soil were identified. In one of the genotypes, the enhanced phosphorus utilization trait is now found to be controlled by a single dominant gene. Physiological analysis showed that the phosphorus efficient genotypes could secret a higher amount of organic acids (such as malic acid, citric acid, succinic acid, etc) into the soil under low supply of phosphorus. The organic acids may assist the solublization of the insoluble phosphorus in the soil. These results shed light on the genetic and physiological basis of phosphorus utilization by wheat plant and suggest that, with appropriate selection strategies, phosphorus efficient wheat varieties can be bred in the future.展开更多
Fluorescence in situ hybridization was applied with total genomic DNA extracted from D.villosum as a probe to characterize chromosome translocations arising from tissue culture in crosses of Triticum aestivum × T...Fluorescence in situ hybridization was applied with total genomic DNA extracted from D.villosum as a probe to characterize chromosome translocations arising from tissue culture in crosses of Triticum aestivum × T. durum D. villosum amphiploids. Chromosome translocations between wheat and D.villosum occurred indeed in callus cells at an average frequency of 1.9 %. Translocations existed not only in callus cells but also in regenerate plants. Three plants with translocation chromosomes were characterized among 66 regenerated plants. One of them was proved to be a reciprocal translocation with break point of wheat chromosome at about one third of a chromosome arm, and that of D. villosum at about one half of a chromosome arm. The break point of the other two translocations was located at, or near centromeres. These similar results from both callus cells and regenerated plants provided evidence that chromosomal translocations could take place in tissue culture. Additional chromosome structure changes (fragments, telocentrics, dicentromeres, and deletions) as well as numerical alterations (including aneuploid and polyploid) were also observed in tissue cultured cells.For 175 regenerated plants arising from immature embryos of crosses between wheat ( Triticum aestivum L.) and 6D/6V substitution stocks, electrophoresis of glutamate oxaloacetate transaminase (GOT) isoenzymes was performed. The GOT V2 enzyme band was absent in two plants (designated as 98R149 and 98R159, respectively). Fluorescence in situ hybridization with total genomic DNA extracted from D.villosum as a probe confirmed the occurrence of translocation between 6V chromosome and an unknown wheat one in the two regenerants mentioned above. 98R149 and 98R159 were immune to powdery mildew ( Erysiphe graminis DC.f.sp. tritici ) inoculation with mix races collected from Hebei Province.These results demonstrated that useful translocations might be produced via tissue culture.展开更多
Translocation lines with useful genes derived from wheat related species are valuable in wheat variety improvement. But it is not easy to produce them. The frequency of translocation line production is usually low in ...Translocation lines with useful genes derived from wheat related species are valuable in wheat variety improvement. But it is not easy to produce them. The frequency of translocation line production is usually low in wheat. So far, most of translocation lines have been obtained by spontaneous translocation method. It was once suggested that univalent chromosomes would mis divide, reunion, and form chromosome translocation at meiosis. This theory has been supported by some experiments. We designed a series of experiments to increase univalent number at meiosis to test if univalent chromosome number was related to translocation frequency. Our results showed that crossing two different wheat alien substitution lines could indeed increase the frequency of chromosome translocations.展开更多
Plant geneticists and breeders pay great attention to the investigation of translocation lines, because it involves the study of chromosomal structure and function, and the transfer of alien chromosomal fragments (gen...Plant geneticists and breeders pay great attention to the investigation of translocation lines, because it involves the study of chromosomal structure and function, and the transfer of alien chromosomal fragments (genes) into wheat. Excellent translocation lines do have direct application in breeding programs. The principles and methods of inducing chromosome translocation lines have been reviewed. The techniques used in inducing chromosomal translocations can be classified into two major types. 1. Regulating the activity of the Ph gene to facilitate the exchange between homoeologous chromosomes so as to create translocation lines. 2. Exploitation of irradiation, tissue culture or gametocidal chromosome induced chromosomal breakage and reunion to obtain translocation lines. In the last decade, we obtained many wheat rye translocation lines from regenerated pollen plants. Among the 10 translocation lines, there were 4 non Robertsonian translocation lines. The non Robertsonian translocation lines,were identified using a range of techniques, including C banding, in situ hybridization and genome or chromosome specific molecular markers. Based on our investigations, we conclude that the non Robertsonian translocation lines arising from anther culture were the products of abnormal mitosis in in vitro cultured cells.展开更多
文摘The American geneticist, E. R. Sears, was the founder of wheat chromosome engineering.He established the monosomic series of common wheat, which greatly facilitated cytogenetic analysis of wheat. However, problems of univalent shift and labor involved in chromosome counting have limited the common usage of these materials. To circumvent these problems, I developed an alternative set of monosomic lines, in which the presence of the univalent chromosome was indicated by the production of blue pigmentation in the aleurone tissue of seeds. The gene(s) responsible for the blue pigmentation were carried on a short chromosomal fragment of Agropyron elongatum. This chromosomal fragment has been transferred to the different chromosomes of common wheat using radiation induced translocation. On the spike derived from a blue grained monosomic wheat (2 n =41, the univalent chromosome carries the gene for the blue pigmentation), four types of seeds are produced. The deep blue seed has 42 chromosomes, the medium blue and light blue seed has 41 chromosomes, and the white seed has 40 chromosomes. The monosomic genotype is easily identified based on the color of the seed, without the use of microscope. So far, blue grained monosomic lines have peoduced 11 of the 21 different wheat chromosomes. In the course of propagating the blue grained monosomics, I found that the fertility of the nullisomic lines (2 n =40, represented by white seeds) could be improved by continued selfing and reselection. Using the resulted self fertile nullisomic lines, I established an efficient procedure for producing alien substitution lines of wheat. The utilization of the blue grained monosomic lines and the self fertile nullisomic lines may facilitate chromosome engineering studies in wheat.
文摘Seed protein content, nutritional balance and processing property of flour are the three major aspects of wheat protein quality. Most Chinese wheat cultivars are comparable to their Western counterparts in terms of seed protein content and nutritional balance. However, relatively few of them possess good processing property. The main reason underlying the poor processing property of hexaploid Chinese wheat varieties is the weakness in gluten strength. Considering that wheat gluten is mainly composed of a mixture of a finite number of storage protein species and that the storage protein species may determine gluten strength through combinatorial controls, we formed the following strategies in our studies on understanding and manipulating the genetic basis of protein quality in Chinese wheat. 1. Genetic analysis. By performing well structured genetic analysis, we hope to identify two types of storage protein genes, those genes whose presence is associated with good processing property (the desirable genes, or the D type genes) and those whose presence is always associated with undesirable processing property (the undesirable genes, or the U type genes). Two sets of genetic analysis are being conducted currently. The aim of the first set of analysis is to obtain nonfunctional mutants for the majority of the genes whose products are present in the gluten. This analysis is expected to yield information on the function of individual members of storage proteins, some of which may be encoded by the D type genes, in gluten strength control. The aim of the second set of analysis is to identify potential genetic factors that may be responsible for causing weakness in gluten strength in Chinese wheat through the use of recombinant inbreed lines. This analysis may produce information on the function of the storage proteins specified by the U type genes. 2. Molecular analysis. On the basis of above genetic analysis, a molecular approach will be undertaken to clone the D and U type genes. The cloned genes will be characterized in terms of genetic diversity in cultivated wheat and wild species related to wheat and potential application in molecular breeding for processing property improvement. Because of the known association between the HMW glutenin subunit 1D×5 and good processing quality, we are now searching wheat related wild species for better versions of the 1D×5 subunit and testing their potential in wheat processing quality improvement. 3. Molecular breeding. The above genetic and molecular analysis should result in sufficient gene and marker resources suitable for wheat processing quality improvement through molecular breeding. The D type genes will be transferred into high yielding, hexaploid wheat varieties using the transgenic technology. The molecular markers linked to the U type of genes will be used to screen breeding materials for an early avoidance of this type of genes in breeding programs. In summary, the combination of theoretical and applied investigations described above should contribute to wheat protein quality improvement in both China and abroad. In the future, wheat quality breeding will be a more productive and efficient enterprise worldwide.
文摘Deficiency of available phosphorus in alkaline soil is a serious problem in northern China. This contrasts with the finding that the total amount of phosphorus in the soil is, actually, very high (over 200 times of its available form). Starting from 1990, my colleagues and I initiated a new research project with a longer term aim to breed phosphorus efficient wheat varieties. From among 500 wheat lines, several genotypes that could tolerate low phosphorus level in the soil were identified. In one of the genotypes, the enhanced phosphorus utilization trait is now found to be controlled by a single dominant gene. Physiological analysis showed that the phosphorus efficient genotypes could secret a higher amount of organic acids (such as malic acid, citric acid, succinic acid, etc) into the soil under low supply of phosphorus. The organic acids may assist the solublization of the insoluble phosphorus in the soil. These results shed light on the genetic and physiological basis of phosphorus utilization by wheat plant and suggest that, with appropriate selection strategies, phosphorus efficient wheat varieties can be bred in the future.
文摘Fluorescence in situ hybridization was applied with total genomic DNA extracted from D.villosum as a probe to characterize chromosome translocations arising from tissue culture in crosses of Triticum aestivum × T. durum D. villosum amphiploids. Chromosome translocations between wheat and D.villosum occurred indeed in callus cells at an average frequency of 1.9 %. Translocations existed not only in callus cells but also in regenerate plants. Three plants with translocation chromosomes were characterized among 66 regenerated plants. One of them was proved to be a reciprocal translocation with break point of wheat chromosome at about one third of a chromosome arm, and that of D. villosum at about one half of a chromosome arm. The break point of the other two translocations was located at, or near centromeres. These similar results from both callus cells and regenerated plants provided evidence that chromosomal translocations could take place in tissue culture. Additional chromosome structure changes (fragments, telocentrics, dicentromeres, and deletions) as well as numerical alterations (including aneuploid and polyploid) were also observed in tissue cultured cells.For 175 regenerated plants arising from immature embryos of crosses between wheat ( Triticum aestivum L.) and 6D/6V substitution stocks, electrophoresis of glutamate oxaloacetate transaminase (GOT) isoenzymes was performed. The GOT V2 enzyme band was absent in two plants (designated as 98R149 and 98R159, respectively). Fluorescence in situ hybridization with total genomic DNA extracted from D.villosum as a probe confirmed the occurrence of translocation between 6V chromosome and an unknown wheat one in the two regenerants mentioned above. 98R149 and 98R159 were immune to powdery mildew ( Erysiphe graminis DC.f.sp. tritici ) inoculation with mix races collected from Hebei Province.These results demonstrated that useful translocations might be produced via tissue culture.
文摘Translocation lines with useful genes derived from wheat related species are valuable in wheat variety improvement. But it is not easy to produce them. The frequency of translocation line production is usually low in wheat. So far, most of translocation lines have been obtained by spontaneous translocation method. It was once suggested that univalent chromosomes would mis divide, reunion, and form chromosome translocation at meiosis. This theory has been supported by some experiments. We designed a series of experiments to increase univalent number at meiosis to test if univalent chromosome number was related to translocation frequency. Our results showed that crossing two different wheat alien substitution lines could indeed increase the frequency of chromosome translocations.
文摘Plant geneticists and breeders pay great attention to the investigation of translocation lines, because it involves the study of chromosomal structure and function, and the transfer of alien chromosomal fragments (genes) into wheat. Excellent translocation lines do have direct application in breeding programs. The principles and methods of inducing chromosome translocation lines have been reviewed. The techniques used in inducing chromosomal translocations can be classified into two major types. 1. Regulating the activity of the Ph gene to facilitate the exchange between homoeologous chromosomes so as to create translocation lines. 2. Exploitation of irradiation, tissue culture or gametocidal chromosome induced chromosomal breakage and reunion to obtain translocation lines. In the last decade, we obtained many wheat rye translocation lines from regenerated pollen plants. Among the 10 translocation lines, there were 4 non Robertsonian translocation lines. The non Robertsonian translocation lines,were identified using a range of techniques, including C banding, in situ hybridization and genome or chromosome specific molecular markers. Based on our investigations, we conclude that the non Robertsonian translocation lines arising from anther culture were the products of abnormal mitosis in in vitro cultured cells.
