构建全基因组导入系中BC1F1群体大小的影响因素研究

全基因组导入系是遗传和育种研究的重要材料。导入系经受体亲本和供体亲本间连续杂交、回交构建而成, BC₁F₁群体大小是获得理想导入系群体的关键参数。然而, 各物种所需要的最小群体尚不清楚, 并且难以通过试验确定。本研究通过编写程序, 模拟减数分裂时的重组过程研究适宜的群体大小, 并通过数学运算和试验验证程序的可靠性。结果表明, 编程模拟与数学计算和试验结果一致。BC₁F₁群体大小与连锁群数目、连锁群长度和基因密度之间均为正相关。当模拟连锁群从5个增加到40个时, 群体大小需要由6.06增加到9.49; 当模拟连锁群长度从80 cM增加到200 cM时, 需要的群体大小从7.14增加到8.64; 当模拟基因密度从每基因20 cM缩小到每基因5 cM时, 群体大小从7.65增加到8.22。为测试该程序的应用范围, 对水稻、小麦、玉米、大豆等主要作物进行了BC₁F₁群体大小模拟,在保证95%的概率覆盖全基因组条件下, 水稻需要的群体最少, 为12个个体, 小麦和大豆均需13个个体, 玉米需要的个体数最多, 为14~15个。     

Breeding by Design-High Throughput Phentyping

Plant evolution under domestication has lead to increased productivity, but at the same time it narrowed the genetic basis of crop species. A major objective in modem breeding is to return to the wild ancestors of crop plants and employ some of the diversity that was lost during domestication for the improvement of agricultural yields. Most of the genetic variation present in wild species has a negative effect on the adaptation of plants to agricultural environments, hence the challenge is to identify and utilize the rare advantageous traits in breeding program. To enhance the rate of progress of breeding based on wild species resources we developed a population of tomato segmental introgression lines （ILs-congenics）. The ILs are comprised of marker-defined genomic regions taken from the green fruited wild species S. pennellii and introduced （through genetic crosses） onto the genetic background of the elite inbred variety M82 （Eshed and Zamir, 1995）. The ILs constitute an ＇exotic library＇ where the entire wild species genome was partitioned among 76 lines each carrying a single homozygous introgressed segment. Implementation of this resource for quantitative trait loci （QTL） mapping is based on the nearly isogenic nature of the lines such that any phenotypic difference between M82 and an IL, or the hybrid of M82 with an IL （ILH）, is attributable to the S. pennellii genomic segments.     

东乡野生稻渐渗系基因组结构变化及多样性分析

[目的]研究东乡野生稻渐渗系基因组结构变化及对其进行多样性分析。[方法]以东乡野生稻(O.rufipogon Griff.,供体)和栽培稻协青早B(O.sativa sp.indica Kato.,受体)构建的BC1F6渐渗群体为研究材料,利用筛选出的分布在12对染色体上的25对SSR引物对群体中的239个株系进行多态性分析。[结果]25个微卫星位点都有东乡野生稻DNA片段不同程度的渗入,群体均大部分保留亲本协青早B或东乡野生稻的DNA序列。渐渗系基因组中平均受体纯合条带百分率为78.13%,最高达94.98%(引物为RM131),最低为60.25%(引物为RM171)。平均供体纯合条带百分率为13.37%,最高达32.64%(引物为RM171),最低为2.93%(RM1095)。群体中还存在一些杂合位点,平均杂合率为5.62%,最高达10.04%(引物为RM401)。此外,BC1F6渐渗群体中发现有双亲条带的丢失和一些双亲所没有的新条带出现,其中平均亲本条带丢失率为2.88%,最高达13.39%(引物为RM311),最低为0(引物为RM401),平均新带率为1%。高世代渐渗群体平均Nei’s基因多样性(He)和平均Shannon’s信息多样性指数(I)分别为0.276和0.457。[结论]通过远缘杂交,渐渗系发生了广泛遗传与表观遗传变异,扩大了遗传变异基础,为水稻品种改良与种质创新奠定了重要基础。     

The Inheritance of Morphological and Biochemical Traits Introgressed into Common Wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) from <Emphasis Type="Italic">Aegilops speltoides</Emphasis> Tausch

The genetic control of morphological characters and gliadin composition was studied in two bread wheat lines with introgressed segments from Aegilops speltoides Tausch. It was found that the transferred trait of leaf hairiness is controlled by one dominant gene, non-allelic to the known gene, Hl1. It was localized in 7B chromosome. Whole plant non-glaucousness is under the control of an inhibitor gene, allelic to the gene W1^I of wheat located on chromosome 2B. This gene was found to be epistatic to the gene controlling spike waxlessness. The introgressed gene for spike glume color was found to be allelic to the Rg1 gene located on 1BS of common wheat, but it was linked with another allele of the gliadin locus Gli-B1.     

Characterization of stem rust resistant derivatives of wheat cultivar Amigo

Summary Originally developed for resistance to greenbug derived from Insave rye, Amigo wheat carries two genes for resistance to stem rust. One of these genes is associated with a rye chromosome 1RS segment carrying the Sec-1 protein marker and presumably greenbug resistance. The second gene which is genetically linked to leaf rust resistance is associated with an Agropyron-derived segment. Rust tests in Canada confirmed that these genes were Sr24 and Lr24. In contrast to Agent and certain 3D/Ag derivatives from Dr. E.R. Sears, the Amigo source of Sr24/Lr24 freely recombined with white seed colour during backcrossing.     

小麦-大麦大穗大粒渐渗系WB13的分子细胞学鉴定

小麦新种质WB13是普通小麦(Triticum aestivum L.)品种7182与农家二棱大麦(Hordeum vulgare ssp.distichon Hsü.)杂交后回交多代衍生而来的大穗大粒材料。为了明确WB13的遗传基础,本研究利用形态学、细胞学、分子标记及特异片段回收测序等技术对其进行了鉴定。结果表明,采用小麦不同同源群简单重复序列(simple sequence repeat,SSR)标记对WB13和小麦7182进行遗传背景分析发现,两者遗传相似系数(genetic similarity coefficient,GS)达97.0%,田间表现为大穗、大粒,综合农艺性状较好;根尖细胞染色体数目为2n=42,以大麦基因组DNA为探针进行基因组原位杂交(genomic in situ hybridization,GISH)未出现杂交信号;利用大麦特异序列标签位点(sequence-tagged site,STS)标记对WB13和农家二棱大麦进行扩增,发现ABG054(4H)和ABC305B(7H)两个标记在WB13中扩增出了大麦特征条带(分别记为WS1和WS3),经测序及序列比对,发现其与扩增到的大麦序列分别具有100%和98%的相似性,与EMBL数据库中的序列比对,与两者有相似性的全为大麦的序列。利用大麦4H和7H染色体上的35对SSR引物对WB13及其亲本进行扩增,发现与千粒重相关的标记MGB396(4H)在WB13中扩增出了大麦的特异条带。综合以上结果确定WB13含有大麦4H和7H染色体的遗传物质,为小麦-大麦渐渗系材料,且4H染色体渗入片段中可能携带与千粒重相关的有益基因。本研究确定了WB13为小麦-大麦杂种后代,此材料的育成丰富了小麦-大麦中间材料和大穗大粒材料的种质资源。同时本研究在分子水平上初步揭示了WB13大穗大粒特性的成因,为后续构建遗传分析群体进行相关数量性状(quantitative trait loci,QTL)定位及推动WB13的研究利用积累了基础资料。     

Genetic diversity of walking catfish, Clarias macrocephalus, in Thailand and evidence of genetic introgression from introduced farmed C. gariepinus

The Thai walking catfish, Clarias macrocephalus Günther, 1864, is economically important to Thailand. It occupies marshes and swamps that are severely endangered due to population expansion and natural populations are thought to be suffering from massive back-crossing with the C. macrocephalus×C. gariepinus hybrids. Therefore, a study on genetic diversity of this species is required to enable efficient conservation and management plans. In this study, 25 natural populations were collected throughout the country, 12 populations from provinces locate in the Chaophraya river basin in the center of the country, 5 from the Mekong river basin, 1 from the east and 7 from the south. One population of hatchery origin was obtained from the Department of Aquaculture, Kasetsart University in Bangkok.

Twelve isozymes and one protein system were analyzed. Among 18 loci resolved, 8 were polymorphic. The number of alleles per locus, average polymorphism and individual polymorphism were significantly higher in collections from the Chaophraya river basin than from the Mekong, east and south. The hatchery population also had relative high genetic variation. Six out of twenty-six populations differed significantly from Hardy-Weinberg equilibrium after Bonferroni correction. None of loci pairs showed significant linkage disequilibrium after Bonferroni correction. The F_st value across loci was highly significant from zero. A neighbor-joining tree reveals that populations from the south were genetically distinct from the remaining populations.

Alleles peculiar to the African catfish [C. gariepinus (Burchell, 1822)] genome were observed in 12 of the natural populations and the hatchery population. This is evidence of genetic introgression which has probably persisted for several generations, since there was no significant genotype disequilibrium between the macrocephalus and gariepinus alleles at three diagnostic loci.     

IRRI野生稻渗入基因系稻瘟病、白叶枯病、褐飞虱抗性鉴定

对65份从IRRI引进的野生稻渗入基因系进行稻瘟病、白叶枯病及褐飞虱抗性鉴定,筛选出34份抗稻瘟病品系,15份高抗白叶枯病品系,35份中抗白叶枯病品系,21份抗褐飞褐飞虱的品系,44份中抗褐飞虱品系,30份兼抗2种病虫害的品系和27份兼抗2种病虫害的品系,以期为育种利用提供新的抗源。     

Potential of wild species for genetic enhancement of some semi-arid food crops

Discovery and incorporation of genes from wild species provide means to sustain crop improvement, particularly when levels of resistance in the cultigens are low and virulent strains of pests and pathogens overcome the host plant resistance. The extent of utilization and the potential of the wild genepool for genetic enhancement were reviewed in five important food crops viz. sorghum, pearl millet, chickpea, pigeonpea and groundnut grown in the semi-arid tropics. Introgression from compatible wild germplasm in the primary gene pool resulted in transfer of new cytoplasmic male sterility systems in pearl millet and pigeonpea, development of high protein, cleistogamous flower and dwarf pigeonpea lines and foliar disease resistant groundnut cultivars. Utilization of wild species in secondary and tertiary gene pools has been generally limited due to sterility, restricted recombination or cross incompatibility. Nevertheless, these species are extremely important as they contain high levels of resistance to several important biotic and abiotic stresses. Several of them, like those belonging to the Parasorghum section and the rhizomatous Arachis species are sources of multiple resistances and hold great promise to sustain crop productivity.     

Identification of AFLP Markers that Discriminate Between Cultivated Cotton and the Hawaiian Island Endemic, <Emphasis Type="Italic">Gossypium tomentosum</Emphasis>Nuttall ex Seeman

Interspecific gene flow from crop species into wild relatives may compromise the genetic integrity of native species and in the case of transgenic crops lead to the escape of transgenes into natural populations. Approximately 72% of the upland cotton (Gossypium hirsutum L.) acreage grown in the United States in 2000 utilized transgenic cultivars. The closest relative of G. hirsutum is G. tomentosum Nuttall ex Seeman, endemic to the Hawaiian archipelago. Because these two species are fully interfertile, cultivation of transgenic G. hirsutum in the Hawaiian Islands is restricted. We investigated the possibility of identifying AFLP genetic markers that are diagnostic for each species and thus could be used in future studies to detect introgression between them. In addition, we were interested in comparing levels and geographic patterns of AFLP diversity in G. tomentosum to previous estimates using allozyme data. AFLP analysis led to the detection of 11 and 16 species-specific markers for G. tomentosum and G. hirsutum, respectively. These species-specific AFLP markers will be useful for detecting gene flow between G. hirsutum and G. tomentosum that has occurred in the past and thus might occur in the future if the restrictions on cultivation of transgenic G. hirsutum are relaxed in the Hawaiian Islands. Little genetic diversity and limited geographic patterning were discovered using AFLP markers, consistent with data from previous allozyme studies.