“三叶”宜昌橙体细胞联会现象观察与分析

对“三叶”宜昌橙有丝分裂中期染色体联会现象进行了初步的观察与分析。结果表明：所观察的154个中期分裂相中发现62个存在染色体联会现象,出现频率约为40.3%;共观察到124个联会复合体,其中以2条染色体之间的联会最多,约占总数的59.6%,其次分别为3条、4条和5条染色体联会复合体,占25.8%、12.9%和1.6%;染色体联会一般以端部—端部、端部—中部连接并形成棒形、V形、U形、Y形、T形和O形等多种构型。本文还对宜昌橙体细胞联会研究意义进行了讨论。     

花生栽培种和野生种的种间杂交研究——Ⅳ.双二倍体的人工合成及其利用前景

通过花粉蒙导作用,由花生属花生区组中具B染色体组的A.batizocoi和具A染色组的A.correntina人工合成了双二倍体。本文从双二倍体杂种的形态特征,育性、杂交亲和性等方面作了分析得出如下结论:双二倍体的营养生长比其亲本和二倍体杂种更旺盛;不育二倍体杂种在染色体加倍形成双二倍体后育性得到恢复并能保持;二倍体杂种的减数分裂不规则。在后期Ⅰ出现落后染色体。双二倍体的染色体联会主要是20个二价体。双二倍体与栽培品种杂交亲和,其F_1代株型趋向栽培品种,减数分裂不规则,单价体较多,花粉育性较低,结荚很少。     

家蚕多倍体的性染色体组成,联会和分离及其性状表现

本文探讨了家蚕四倍体雌的性染色体的联会，分离形式及三倍体雌的染色体组成与产卵性状的关系。１）四倍体雌在减数分裂时，绝大多数呈Ｚ－Ｚ联会，分离，Ｗ不参加联会，随机分向两极或同时进入某一极；Ｚ－Ｗ联会，分离的频率很小。四倍体雌Ｘ二倍体雄的三倍体子代的形态笥状的分离符合５：１的理论值，其染色体组成有３Ａ＋ＺＺ，３Ａ＋ＺＺＷ，３Ａ＋ＺＺＷＷ，３Ａ＋ＺＺＺ，３Ａ＋ＺＷＷ５种，呈１５：６７，６：１５：１．２：     

Fluorescent in situ hybridization — a useful aid to the introduction of alien genetic variation into wheat

Summary Fluorescent in situ hybridization (FISH) of DNA to plant chromosomes has proved to be a powerful cytogenetic tool. The value of fluorescent in situ hybridization of total genomic DNA (GISH) of related species is demonstrated in the determination of wheat/alien chromosome pairing in hybrids. Its use for assessing the relative merits of the various genes that affect chromosome pairing is also shown.The ability of GISH to identify the presence in wheat of whole alien chromosomes or alien chromosome segments is illustrated. The potential of FISH for detecting repeated DNA sequences, low copy sequences and single copy genes is discussed.Abbreviations FISH fluorescent in situ hybridization - GISH genomic in situ hybridization - PRINS primer-induced in situ hybridization     

Elymus canadensis×Secale cereale Amphiploids. II. Chromosome Constitutions and Pairing of Open-Pollinated Progeny

Eleven C₂ and two C₃ 0pen-pollinated plains from Elymus canadensis × Secale cereale amphiploid plants (2n = 6x = 42, SSHHRR) were examined for chromosome constitution and meiosis. Chromosome numbers of the progeny varied: 2n = 26, 27, 28, 36, 37, 39, 40, and 41. Elimination of portions of genome constituents were made at random and were irregular in all o the progeny. Monosomic (2n = 41) and nullisomic (2n = 40) plants lost one to two E. canadensis or S. cereale chromosomes and showed average of 17 to 18 bivalents and 4 to 5 univalents per cell at Ml. The C₂, aneuploid plants with 36 to 41 chromosomes seemed to result from selfing or intercrossing among; the C₁ amphiploid plants, while the plants of 2n = 26 to 2S (6–9 II + 10–141) might originate from outcrosses of the C_l amphiploid to S. cereale. Bivalent pairing might be preferentially intragenomic (S-S, H-H, or R-R). The occurrence of multivalents indicates a low potential of both intragenomic and intragenomic pairing; Pollen of the lour plants showed poor stainability (1 to 13 %) and no seed set in any of the progeny.     

Cytogenetic study of Helianthus laevigatus and its F1 and BC1F1 hybrids with cultivated sunflower, Helianthus annuus

Although the wild sunflower species Helianthus laevigatus has not been extensively studied it may be considered for sunflower breeding as a potential source of desirable genes for Sclerotinia stalk rot resistance and high contents of proteins and linoleic acid in the seed. A set of six H. laevigatus populations was crossed to cultivated sun~ower lines and produced nine F₁ (2-14 plants) and 66 BC₁F₁ hybrid combinations (1-13 plants). Male sterility occurred in F₁ and BC₁F₁ hybrid combinations and pollen viability was lower in the progenies than in the parents (51.6-77.2%in F₁ and in F₁ and 4.8-34.0% in BC₁F₁). Meiosis was normal in the H. laevigatus populations It was found that this tetraploid species also occurred in a hexaploid form Numerous irregularities were observed in the meiosis of the F₁ interspecific hybrids During diakinesis, quadrivalents and hexavalents were recorded in addition to bivalents Dislocated chromosomes and chromosome bridges were present in the other phases The chromosome number in F₁ was 68 (tetraploid). Irregularities in chromosome pairing were observed in the interspecific hybrids at BC₁F₁. There were many univalents, and trivalents quadrivalents and hexavalents were also present The chromosome number in the BC₁F₁ generation ranged from 34 to 60. The occurrence of meiotic irregularities in the F₁ and BC₁F₁ interspecific hybrids indicates that H. laevigatus and the cultivated sunflower differ in genome constitution.     

Genotypic control of chromosome pairing in amphiploids involving the cultivated oat Avena sativa L.

Summary A genotype of the diploid species Avena longiglumis (Cw 57) has been shown to modify the genetic control of diploid-like chromosome pairing in the cultivated oat, A. sativa (2n=6x=42) leading to increased homoeologous chromosome pairing in 4x hybrids between the two species (Rajhathy & Thomas, 1974). The Cw 57 genotype has a similar effect in increasing homoeologous chromosome pairing in amphiploids combining diploid and hexaploid genomes including associations between alien chromosomes and their corresponding pairs in hexaploid species. The effect of the Cw 57 genotype is probably in altering the specificity of chromosome pairing in the early stages of meiosis. The use of the Cw 57 genotype to induce homoeologous chromosome pairing as a technique for the transfer of desirable alien variation into the cultivated oat is discussed.     

Breeding for hard red winter wheat cultivars adapted to conventional-till and no-till systems in northern latitudes

Summary Monosomic alien addition lines combining individual F. drymeja chromosomes and the L. multiflorum complement were isolated from the cross between the triploid hybrid L. multiflorum (4x) × F. drymeja (2x) and diploid L. multiflorum (2x). Chromosome pairing in the addition lines was studied at metaphase 1 of meiosis and the relationship between single F. drymeja chromosomes and the corresponding homologous pair in L. multiflorum is discussed. Trivalent frequency in the addition lines was higher than expected from observations of chromosome pairing in the triploid hybrid and there were differences between lines in the number of trivalent associations formed. There is some evidence to suggest that trivalent frequency is not entirely dependent on chromosome length and that transmission of the alien chromosome in the female is dependent on the size of the added chromosome. Morphological studies were made to assess the phenotypic effects of the addition of single F. drymeja chromosomes to the L. multiflorum complement. Two plants (2n=14) with recombination between a L. multiflorum and a F. drymeja chromosome were identified.     

Cytological analyses of hybrids and derivatives of hybrids between durum wheat and Thinopyrum bessarabicum,using multicolour fluorescent GISH*

The wheat progenitors and other wild relatives continue to be important sources of genes for agronomically desirable traits, which can be transferred into durum wheat (Triticum turgidum; 2n = 4x = 28; AABB genomes) cultivars via hybridization. Chromosome pairing in durum × alien species hybrids provides an understanding of genomic relationships, which is useful in planning alien gene introgression strategies. Two durum cultivars, ‘Lloyd’ and ‘Langdon’, were crossed with diploid wheatgrass, Thinopyrum bessarabicum (2n = 2x = 14; JJ), to synthesize F₁ hybrids (2n = 3x = 21; ABJ) with Ph1. ‘Langdon’ disomic substitution 5D(5B) was used as a female parent to produce F₁ hybrids without Ph1, which resulted in elevation of pairing between durum and grass chromosomes – an important feature from the breeding standpoint. The F₁ hybrids were backcrossed to respective parental cultivars and BC₁ progenies were raised. ‘Langdon’ 5D(5B) substitution × Th. bessarabicum F₁ hybrids were crossed with normal ‘Langdon’ to obtain BC₁ progeny. Chromosome pairing relationships were studied in F₁ hybrids and BC₁ progenies using both conventional staining and fluorescent genomic in situ hybridization (fl‐GISH) techniques. Multicolour fl‐GISH was standardized for characterizing the nature and specificity of chromosome pairing: A–B, A–J and B–J pairing. The A–J and B–J pairing will facilitate gene introgression in durum wheat. Multicolour fl‐GISH will help in characterizing alien chromosome segments captured in the durum complement and in their location in the A and/or B genome, thereby accelerating chromosome engineering research.     

滇Ⅰ型粳稻不育系原种提纯技术研究*

 采用单株选择（不育系和保持系花粉镜检）、成对回交、株系鉴定、混系繁殖，辅以在开花期去除不育系中异杂株的方法提纯滇Ⅰ型不育系；经田间种植鉴定，原种纯度达99.90%以上；缩短了种子生产年限，减少繁殖代数，有效地保持了不育系原有的配合力和典型性状。达到“起点高、防杂严、数量大、程序简”的目的。