abstract
Wheat is the largest and most important food crop in the world. It is a very important research field in modern crop genetics and breeding to introduce foreign excellent genes into cultivated crops by biotechnology and broaden the genetic basis of wheat breeding.
Wheat (common wheat, 2n = 4x-42, AABBDD) and agropyron cristatum were cultivated. P genome) (Agropyron cristatum is a taxonomic concept of modern wheat plants here, not a generalized concept of Agropyron cristatum in the traditional sense, that is to say, it is completely different from the traditional concept that some wheat geneticists call agropyron elongatum and agropyron intermedium agropyron. Hybridization between plants can be traced back to 1930s (White,1940; Smith,1942; Dewey, 1984), but it was not until the 1990s that scholars reported the success of wheat and agropyron (Li Lihui et al., 1990,1995; Li & Dong,1991; Chen et al.1990; Limin & Fowler,1990; Ahmed & ampComeau,1992; Jauhar, 1992). Although some foreign scientists listed here have also obtained hybrids between wheat and Agropyron, it is still unclear which genes of Agropyron should be transferred to wheat due to the blindness of exotic species selection (Chen et al.,1990; Jauhar, 1992), or the high sterility of F 1 (Ahmad & amp； Comear, 1992), or the target gene to be transferred is difficult to express in wheat background (limin &; Fowler, 1990) and other reasons, but basically gave up the research work in this area (private letter, 1997).
In this study, we used the common wheat variety Fuhao (Chun, with 3 pairs of hybridizable genes and excellent agronomic characters, native to Japan) as the female parent and three agropyron cristum as the female parent.
1. Scientific selection of distant hybridization parents laid a solid foundation for successful hybridization and foreign excellent gene transfer. In the process of selecting foreign donor varieties, the agronomic characters, stress resistance and disease resistance of thousands of wild relatives of wheat were jointly identified by the Institute of Crop Variety Resources and the Institute of Plant Protection of China Academy of Agricultural Sciences, the Australian Plant Industry Division, the Australian Federal Scientific and Industrial Research Organization, the Canadian Cytogenetics Division, the Ottawa Research Station, and the Canadian Ministry of Agriculture. Then, according to the comprehensive identification results, three wheatgrass-the best foreign donor varieties used in this study were selected. Because these three kinds of agropyron cristatum not only have many excellent genes (traits) that other exotic species can't match, including reasonable plant type structure (plant height is less than 60cm, stem length below ear accounts for about 2/3 of plant height, effective tillering >; 50. The leaves are narrow, short and erect), the panicle is large with many grains (more than 65,438+050 grains per panicle), the grains are black, the protein content is high, the drought resistance and cold resistance are strong, the salt tolerance is moderate, and it is immune to three kinds of rust, powdery mildew and yellow dwarf disease, and highly resistant to scab. More importantly, the above excellent genes are urgently needed in wheat breeding.
2. Using modern distant hybridization method and young embryo rescue technology, the hybrid between common wheat and partially self-bearing agropyron cristatum was obtained for the first time in the world. It was found that using agropyron cristatum from different sources as the male parent, not only the hybrid seed setting rate was different, but also the phenotype of hybrid F 1 was different. This result, on the one hand, breaks through the previous conclusion (Dewey, 1984) that Agropyron cristatum P genome has an independent genetic status in the wheat family and cannot be crossed with wheat; On the other hand, the hybrid F 1 is partially self-fertile, which lays a solid material foundation for the successful transfer of foreign genes.
3. Using young panicles of hybrid F 1 as explants, somatic clonal variation was induced from callus. It is found for the first time that the self-fertility of hybrid F 1 is from scratch (0? 0.032%), or significantly increased (10 times). This discovery is very important because it shows people a bright prospect, that is, it is possible to realize foreign gene transfer in hybrid F 1 by this technology.
4. Through careful analysis, some genetic mechanisms were clarified for the first time. First, the self-fertility of hybrid F 1 is due to the fact that two P chromosomes contain genes that control chromosome segregation during meiosis, thus forming functional near-equal 2n or non-meiotic gametes; Secondly, 1 P chromosome has a genetic factor that inhibits the Ph gene of wheat, and can induce chromosome pairing between Agropyron cristatum P genome and wheat A, B and D genomes; Thirdly, it is confirmed that the gene exchange between wheat and agropyron cristatum can be realized by spontaneous translocation between chromosomes. These findings, on the one hand, completely broke through the judgment of international authoritative organizations that "gene exchange between wheat and agropyron cristatum is impossible", on the other hand, provided important theoretical guidance for transferring excellent genes of agropyron cristatum more purposefully and efficiently.
5. Using comprehensive techniques such as backcross, selection, morphology, cytology, allozyme and genome in-situ hybridization detection, the 1 1 genetically stable wheat-agropyron cristatum alien double addition line was bred for the first time, and feasible methods for effectively producing the alien double addition line (line) were put forward. The generation of heteroduplex addition lines is an important tool to study the genetic effect and effective utilization of genes on each P chromosome with wheat as the background.
6. A batch of new germplasm with excellent genes of Agropyron cristatum was created for the first time, with stable heredity (2n = 42,265,438+0II, heterotopic translocation line or substitution line), which can be used for breeding and production. Its general characteristics are: more effective tillers (15~82 panicles/plant); The plant height is 70 ~ 95 cm, and the stem below ear accounts for about1/2 of the plant height; Flag Ye Ting Li; Large panicle type (55 ~ 1 12 grains per panicle); The appearance of the grain is white or black, and the protein content is high (17. 1~20.7%). 1000-grain weight >; 38g has good comprehensive disease resistance (powdery mildew, stripe rust, yellow dwarf and scab), cold resistance and drought resistance, especially some new germplasm have super-high yield potential (theoretical yield is higher than 600kg/mu). At present, these new germplasm have been used by 15 breeding units in 9 major wheat producing provinces in China, and 5 new germplasm from Shaanxi and Shanxi are participating in yield comparison tests.
7. The genetic analysis of the black seed gene and powdery mildew resistance gene in the obtained black seed (2n = 42, 265, 438+0II, alien translocation line) and new powdery mildew resistance germplasm (both from Agropyron cristatum) proved that both of them were dominant single gene inheritance.
Key words: common wheat (L., 2n = 6x = 42, AABBDD); wheatgrass
Introduction of excellent genes in agropyron cristatum. Transformation of common wheat by biotechnology
Doctoral student: Li Lihui.
Tutor: Professor Yu
(Institute of Crop Germplasm Resources, China Academy of Agricultural Sciences, Beijing, 10008 1)
abstract
Like most other crops, the genetic variation of cultivated wheat has been greatly eroded under the modern agricultural system. Genetic erosion not only limits the further improvement of wheat yield and quality, but also makes wheat more and more vulnerable to biological and environmental stresses. There are a lot of genetic variations in wild related species of cultivated wheat. Introducing genetic variation from exotic species is a valuable method to increase the genetic diversity available to wheat breeders.
In this experiment, young embryos were saved by artificial culture medium, and the interspecific hybrid of common wheat variety Fukuho (2n=6x=42, AABBDD) and three tetraploid agropyron cristatum (2n=4x=28, PPPP) was synthesized. These hybrids can be used to: (1) transfer the ideal characters of agropyron cristatum to common wheat; (2) To determine the effect of P genome on the self-fertility of interspecific hybrids; And (3) producing a wheat-agropyron dichotomous addition line. Through the study of intergeneric hybrids and their derivatives, the following results were obtained:
1. Agropyron cristatum may be one of the most potential foreign donors for wheat improvement. Ice grass. It is a small genus with no more than 10 species. According to the terminology of many modern botanists, they form the so-called "Agropyron cristatum complex" together with the P genome. Celosia cristata is the model species of this genus. All species of this genus are very precious; They are mainly cultivated as forage plants and are famous for their high drought tolerance and cold tolerance. Some species have been successfully used to fix quicksand. In addition, through the evaluation of all the new wheat germplasm resources in northern China, it was found that the crested wheat also had other characters with potential value for wheat improvement. These include shorter stems (usually less than 60 cm), more tillers and florets, immunity to wheat diseases such as rust, powdery mildew and barley yellow dwarf virus (BYDV), and resistance to wheat scab.
2. The seed setting rate (0.22%~0.63%) and the degree of plant development were different in the three hybrid combinations. Each plant obtained from Fukuho with the registration numbers Z540 and Z602 respectively is stunted. The former died before heading. Although the latter produced two ears, neither self-bred seeds nor backcross seeds were obtained from these two ears. Two plants obtained from fuku ho×a cristagum Z559 showed vigorous tillering. The results showed that the mating ability of the three agropyron cristatum used in this experiment was different from that of Fuhe. Observing the root tips of all hybrid seedlings, it was found that the number of somatic chromosomes of each hybrid seedling was 2n=35 as expected.
3. The self-bearing interspecific hybrid between ordinary wheat variety Fukuho (2n=6x=42, AABBDD) and tetraploid agropyron cristatum (2n=4x=28, PPPP) was obtained for the first time. Contrary to the report that BC 1 derivative was not obtained from wheat-agropyron cristatum hybrid or it was difficult to obtain BC6543 8+0 derivative, in Fukuho× agropyron cristatum Z559 hybrid, they not only had high seed setting rate (15. 1%) but also had partial self-fertility. The average configuration of hybrid in meiotic metaphase ⅰ is 24.47 i+4.32 rod ⅱ+0.71ring ⅱ+0. 14 Ⅲ+0.0 1 Ⅳ. According to different chromosome sizes, some bivalents in each cell are obviously heteromorphic, indicating that these bivalents are heterozygous. In the later stage I, chromosome segregation mainly means that most of the 35 chromosomes (16~30 chromosomes) gather in one pole, so that the larger daughter cells receiving most of the 35 chromosomes may develop functional gametes.
4. In order to induce somaclonal variation, the hybrid young panicles of common wheat variety Fukuho and Agropyron cristatum Z559 were cultured. Although the regenerants showed no variation in chromosome number, they did show a higher degree of meiotic instability than the original hybrids. Especially in regenerated plants, the self-seed setting rate is greatly improved, from 0.034% to 0.33%. As a result, a total of 6 1 seed was obtained. It is rare for Fukuho× Agropyron Z559 to obtain so many self-bred seeds among intergeneric hybrids of wheat, which laid a solid foundation for transferring the required genes from Agropyron cristatum to common wheat.
5. The methods of morphology, cytology, isoenzyme and genome in situ hybridization were used to analyze the inbred and backcross offspring. The results show that all plants with exotic traits carry genetic material of P genome. At the same time, 1 1 diploid alien addition lines were obtained.
6. After summarizing and analyzing all the cytological data obtained in this experiment, some conclusions can be drawn. They are: (1) Aspergillus cristatus Z559 used in this experiment carries a genetic system that inhibits Ph activity, which may mainly involve a P genome; (2) The P genome contains genes that control chromosome segregation in the later stage of meiosis, and these genes may mainly involve two P chromosomes; And (3) spontaneous wheat-agropyron translocation can occur in selfing and backcrossing derivatives.
7. In this experiment, another very important result is that some new germplasms containing foreign genes are obtained. They showed more effective tillers (65438+ 05-82 panicles per plant), the plant height ranged from 70 to 95 cm, with 55- 1 12 grains per panicle, BYDV the protein content was higher (17. 1-20.7%). So far, all the new germplasm obtained in this experiment have been used by China 15 wheat breeding institutions.
8. The new germplasm with black grain color and resistance to powdery mildew was analyzed. Genetic analysis showed that these two traits were both from Agropyron cristatum Z559, which were controlled by a dominant gene.
Key words: common wheat, agropyron cristatum, interspecific hybrid, self-fruiting, alien addition and translocation lines, genetic analysis.