Fragile×expression and×inactivation

Summary The inactive fragile×chromosomes of a 47,fra(X),fra(X),Y male with a typical fragile×phenotype were successfully separated from the active homologues by means of somatic cell hybridization. It was shown by FUdR-induction and caffein-posttreatment that the separated inactive×chromosomes expressed their fragile sites and that the presence of an active mutated \sxchromosome was not a prerequisite for fragile X expression. The fragility seems to be an intrinsic property of the individual fragile site. This result is in favour of the classical concept that the fragile site at Xq27.3 has a primary pathogenetic function in this syndrome, although the fragility itself could represent a secondary phenomenon related to an unknown alteration of the DNA in this chromosome region. It is also concluded that inactivation of the fragile\sxchromosome in females is not responsible for either false negative fragile\sxfindings or the observation of fragile\sxnegative colonies isolated from fragile\sxpositive fibroblasts in heterozygotes.     

Production of trigeneric (barley × wheat) × rye hybrids

Summary Rye (Secale cereale cv. Prolific 2n=14 and 2n =14 + 2B was crossed onto hybrids between barley (Hordeum vulgare 2n = 14) and wheat (Triticum aestivum 2n= 42). Pollinated florets were injected with GA₃ to promote fertilization and hybrid embryo development. At 16 days after pollination the watery caryopses were removed, embryos dissected and cultured on a modified B₅ medium. Approximately 20% of the cultured embryos produced both roots and coleoptile and developed into viable seedlings. Viable seeds were also obtained at a low frequency from the same cross combinations. The hybrids were wheat-like except for the hairy neck characteristic of rye. There were 35 chromosomes in somatic tissue; 21 wheat, 7 barley and 7 rye. The rye chromosomes were distinguishable by their larger size and terminal C-bands. A lower seed set was obtained using pollen from rye plants with 2n=14 + 2B chromosomes than from plants without B chromosomes.Contribution No. 577, Ottawa Research Station     

甘薯(6×)×海滨野牵牛(4×)种间杂种过氧化物酶同工酶分析

植物杂种的遗传分析,除应用形态学、细胞学等方法外,尚可利用同工酶分析技术。在这方面,国内李继耕等对玉米杂种;易琼华等对杂交稻;吴郁文等对小麦、黑麦和小黑麦;李玉湘对油菜与白菜的种间杂种等都进行了同工酶分析,展示了同工酶分析杂     

Post-zygotic gametic selection due to endosperm balance number explains unusual chromosome numbers of 3×× 2× progeny in Solanum

 Crosses between triploid and diploid genotypes are usually the best sources of trisomics in potato as well as in several other crop species. However, 3×× 2× crosses between triploid (2n=3×=36; 2EBN) Solanum commersonii-S. tuberosum hybrids and diploid (2n= 2×=24; 2EBN) genotypes gave progenies with a high number of extra chromosomes, 29–36, suggesting that only eggs with 17–24 chromosomes produced embryos that reached full development. Our hypothesis is that although triploids produce eggs with a range of chromosome numbers, 3×× 2× crosses involving a 2×(2EBN) parent favor eggs with a high chromosome number. These eggs have higher probabilities of possessing the same endosperm balance number (EBN) value (i.e. 1) of gametes produced by the 2EBN diploid parent to give the required 2:1 maternal to paternal EBN ratio in the hybrid endosperm. Under this model, trisomics are produced only if the diploid parent has an EBN of 1. Based on our results and those reported in the literature, it is proposed that in 3×(2EBN) × 2×(2EBN) crosses the endosperm balance number exercises negative selection for gametes with a low chromosome number, and a corresponding low EBN, and positive selection for gametes with a high chromosome number and EBN. Received: 2 April 1998 / Revision accepted: 27 October 1998     

Characterization of somatic embryogenesis in Pelargonium××hortorum mediated by a bacterium

Several cultivars of hybrid seed geranium (Pelargonium×hortorum Bailey), previously shown to be recalcitrant in culture, produced somatic embryos at high frequency when explants were co-cultivated with a morphogenesis promoting bacterium. This bacterium was isolated as an in vitro contaminant from cultures of geranium seedling explants and identified as belonging to the genus Bacillus and species circulans. Co-cultivation of hypocotyl explants with the bacterium promoted somatic embryo formation and improved both the frequency and quality of somatic embryos. In the cultivar Ringo Rose, the least responsive among the cultivars screened, the embryogenic response was more than four times that of axenic cultures. Nearly 70% of these embryos converted into plantlets, while the somatic embryos induced under axenic conditions developed poorly and plantlet formation was inconsistent. Among the different treatments of bacterial culture tested (autoclaved culture, culture filtrate, sonicated bacterial culture, sonication of bacterial culture followed by filtration, HPLC fractionation of crude bacterial lysate), only two HPLC fractions promoted embryogenesis to a marginal degree. Co-cultivation of the explants with bacterium during the first week of induction was crucial for obtaining high-frequency embryogenesis, indicating the role of bacterial stimuli during the induction process. Received: 23 June 1998 / Revision received: 20 August 1998 / Accepted: 27 October 1998     

Naked Oat×Maize Hybridization

There is a certain frequency of fertilization and embryo productivity in naked oat (Avena nuda L. ) × maize (Zea mays L. ) crosses. The maize pollen readily germinated on the naked oat stigma and more than one pollen tubes grew into the style in about 68% of florets. In a sample of 163 florets fixed after pollination, 5 (3.07%) had only an embryo, 3 (1.84%) had only an endosperm and 10 (6.13%) had both. Overall, 9 haploid and 3 diploid naked oat plants were obtained from 12 seeds which formed following application of maize pollen to about 2200 emasculated naked oat florets. Preliminary studies indicated that elimination of the maize chromosomes occurred early in the embryo and endosperm development. This method gives a new approach for obtaining haplo!d naked oat.     

FISH分析栽培高粱×拟高粱、甜高粱×拟高粱的染色体行为

采用荧光原位杂交技术对45S rDNA在栽培高粱×拟高粱、甜高粱×拟高粱F1的有丝分裂和减数分裂染色体进行定位研究。在有丝分裂中期染色体上2个杂种分别检测到2个杂交信号, 在减数分裂粗线期、终变期、中期Ⅰ染色体上45S rDNA位于一个二价体上, 说明这两个杂种携带45S rDNA的染色体为同源染色体。根据45S rDNA位点随细胞减数分裂过程的位置变化, 表明这两个杂种染色体配对行为正常, 平均构型为2n=2x=20(10Ⅱ), 证明45S rDNA可作为染色体的一个识别指标间接地观察细胞减数分裂过程染色体的变化行为。     

Somatic Embryogenesis in Abies Alba × Abies Alba and Abies Alba × Abies Nordmanniana Hybrids

Maturation and germination of somatic embryos of hybrids A. alba × A. alba and A. alba × A. nordmanniana were followed by protein analysis of single embryogenic -suspensor masses (ESM) and analysis of storage protein accumulation during somatic embryo development. Very important step was one week pre-cultivation of ESM on medium with polyethylene glycol (PEG) and abscisic acid (ABA). Low osmotic potential of maturation medium and addition of ABA supported development of somatic embryo. Also partial drying of somatic embryo during following three weeks was needed for its normal development. In spite of morphologically fully developed, the somatic embryos were not physiologically ready for germination at least in terms of storage protein accumulation.     

鳙_♀×(鳙_♀×鲢_♂)♂回交育种试验报告

我们自1968—1974年对鳙♀×x(鳙♀×鲢),回交鱼进行受精过程、胚胎、形态、食性和生长等一系列生物学特性的研究,阐明了下列两个问题: 1.鳙、鲢杂交后代与亲本鳙鱼回交,所得到的回交鱼出现杂交优势——回交鱼的(鳃耙排列整齐者)生长速度,无论在鱼种阶段或成鱼阶段都比祖传的良种鳙鱼较快;有常规的受精细胞学程序,受精卵在水温22—24℃的条件下,经26.5小时左右胚胎以头部破膜孵出,畸形率     

Ogura CMS紫菜苔×萝卜×甘蓝型油菜杂种的获得及细胞遗传学研究

以OguraCMS紫菜苔×萝卜杂种F1(AR ,2n =19)为母本 ,以甘蓝型油菜 (AACC ,2n =38)为父本进行杂交 ,获得了 4棵杂种植株。其中 1株 (PRN 1)的花色为嵌合体 ,该植株上的花多为黄色 ,但是也有乳白色花 ,另外还有 1朵花甚至 1个花瓣上同时具有黄色和白色区域 ,其余 3株 (PRN 2、 3、 4 )都开白花。PRN 4的花药开花前退化 ,其余 3株都可以看到 3～ 6枚花药 ,能够产生部分花粉 ,但是PRN 2的花粉不能被I2 KI溶液染色。PRN 2具有 4个蜜腺 ,PRN 1和PRN 3具有 2个蜜腺 ,PRN 4无可见蜜腺。在低温下PRN 2叶色正常 ,其余 3株幼叶表现不同程度缺绿。PRN 1的染色体数目为 2n =38,染色体平均配对构型为 14 6 7Ⅰ +10 0 7Ⅱ +1 0 6Ⅲ ,其染色体组构成可能是AACR ;PRN 2的染色体数目为 2n =35 ,染色体平均配对构型为 13 89Ⅰ +8 33Ⅱ +1 33Ⅲ +0 11Ⅳ ,PRN 3的染色体数目为2n =33,染色体平均配对构型为 14 0 0Ⅰ +7 82Ⅱ +1 0 0Ⅲ +0 0 9Ⅳ。PRN 4的染色体数目未能确定。与甘蓝型油菜回交后PRN 1～ 3植株各自产生了一定数量的种子 ,而PRN 4则未产生种子。对这些杂种及其后代的遗传及育种意义进行了讨论     

Isozyme analysis of progeny derived from (Allium fistulosum ×Allium cepa) ×Allium cepa

Summary Relatively large quantities of seed were obtained from the interspecific backcross (A. fistulosum xA. cepa) ×A. cepa allowing, for the first time, an extensive study of the heritable traits exhibited by backcross progeny. Two backcross populations, BC1034 and BC1040, distinguished by differentA. fistulosum parents, were characterized for the isozyme markersIdh-1, Adh-1, andPgi-1. Statistical methods are described to calculate cell probabilities for a mixed population of F₂ and BC₁ progeny, using an estimate of the fraction of F₂ progeny in the population derived from the isozyme data. Cell probability distributions were calculated for a mixed population with independent pairs of loci and a mixed population with nonindependent pairs of loci. The isozyme lociIdh-1 andPgi-1 appear to be linked, with a map distance estimated at 33 centimorgans (cM) in BC1034 and 42 cM in BC1040. The probability distribution model for linked loci did not account for all of the distorted segregation ratios inIdh-1 ×Adh-1 orPgi-1 ×Adh-1. The cytological literature does not support linkage betweenIdh-1 ×Adh-1 orPgi-1 ×Adh-1. The distorted segregation ratios for these pairs of loci are likely the result of genetic incompatibilities between the two species.Journal Article No. 1578, Agricultural Experiment Station, New Mexico State University, Las Cruces, NM, USA     

鳙♀×(鳙♀×鲢♂)♂回交鱼胚胎、幼鱼发育研究

关于鱼类的胚胎、胚后发育的研究工作,国外的鱼类学家在这方面进行了许多工作,而且找出了一般规律,确立了硬骨鱼类发育阶段的理论。我国的鱼类学工作者对草、鲢、鳙、鲤、非洲鲫鱼等淡水养殖鱼类的胚胎、幼鱼发育的研究,也进行了许多细致深入的工作,积累了颇为丰富的观察研究资料,并把研究成果应用于渔业生产实践,取得了一定的成就。但是国内、外对于杂交种胚胎、胚后发育的研究较少,更由于生产的需要,回交鱼具有生长优势,进一步推广应用吋需要这方面的理论指导,为此,我们在品种改良和培育过程中,对鳙_(♀x)(鳙_(♀x)鲢_(?))_(?)回交鱼胚胎、幼鱼的发育进行初步观察,目的在于:(1)为今后进一步探求回交杂种的胚胎、幼鱼发育的规律,打下基础。(2)在掌握此回交鱼发育阶段形态特征的基础上进一步研究其所要求的生活条件,为培育回交杂种提供合理饲养的资料。     

Interpretation of variety × sowing date × sowing depth interaction for bean–Fusarium–Rhizoctonia pathosystem

Through this study, the sowing date?×?sowing depth?×?variety interaction for Rhizoctonia root rot (RRR) development was investigated in field trials over two growing seasons. Four-way Wald tests indicated that there was a lower RRR incidence in var. Red compared to var. White in the majority of experimental plots. At a 5?cm seeding depth, RRR incidence for plantings on 22 May and 5 June was often lower than that for 5 May date. A hierarchical cluster analysis grouped experimental plots using averages of RRR incidence, Fusarium root rot (FRR) index and the number of seeds per plant. Sowing depth influenced FRR, RRR and productivity more than variety and date factors. Comparison of clusters recognised lower disease and greater production levels for sowing on 22 May and 5 June at 5?cm depth. Thus, shallow seeding of bean varieties in late spring should be incorporated into FRR–RRR-control programmes.     

2× genomes - depth does matter

Background  

Given the availability of full genome sequences, mapping gene gains, duplications, and losses during evolution should theoretically be straightforward. However, this endeavor suffers from overemphasis on detecting conserved genome features, which in turn has led to sequencing multiple eutherian genomes with low coverage rather than fewer genomes with high-coverage and more even distribution in the phylogeny. Although limitations associated with analysis of low coverage genomes are recognized, they have not been quantified.     

Heterosis × nutrition interaction in Drosophila melanogaster

Summary The relationship between heterozygosity and the expression of heterosis at two different nutrition levels was investigated using Drosophila melanogaster. Average daily egg production and egg hatchability were measured in two parental strains and in F₁, F₂ and reciprocal backcross generations. Heterosis was more pronounced in the poor nutritional conditions. Two electrophoretic markers used to estimate the level of heterozygosity in F₂ and backcrosses revealed an excess of heterozygous genotypes. Quantitative genetic effects (an additive line effect and individual and maternal heterosis) were estimated for both traits in the two environments. Although this model gave a reasonable fit in most cases, some epistatic interaction would have to be invoked in order to explain fully the results.     

Genotype × region and genotype × production level interactions in Holstein cows

The identification of the presence of genotype by environment interaction effects on important traits in Holstein cattle allows for the use of international genetic evaluations and a more efficient design of regional genetic evaluation programmes. The aim of this study was to determine the genotype × environment interaction effects in Chilean Holstein dairy cattle through the analysis of records corresponding to calvings between 1998 and 2015. Herds were classified in the central and southern regions of Chile based on herd location as well as by high and low levels of production environments based on the fat plus protein yield averages per herd within each region. The central region has a Mediterranean climate and a confined production system while the southern region has a humid temperate climate and a production system based on grazing with supplementation. Traits studied were milk yield (MY), fat yield (FY), protein yield (PY), fat content (FC) and protein content (PC) by lactation, age at first calving (AFC) and calving interval (CI). Several four-trait mixed animal models were applied to environmental category data as different traits, which included herd-year-calving season (herd-year-birth season for AFC) and lactation number as fixed effects, and animal additive genetic, sire-herd, permanent environment and residual effects as random effects. Genetic correlations (r_g) for MY, FY, FC, PC and CI were found to decrease as differences between environmental categories increased. The r_g between the most extreme environmental categories considered in this study for AFC (0.26) was the only one found statistically lower than 0.60. Genetic correlation values statistically lower than 0.80 (P < 0.05) were observed for AFC, CI, MY, FY and PY between some environmental categories. If separate genetic evaluations are adopted as practical criteria when the value of r_g is lower than 0.60, the consequence of improving a multi-trait economic breeding objective in this population is likely to be small unless extreme environmental categories are considered. However, a moderate decrease in selection response and re-ranking of selection candidates is expected for AFC, CI and yield traits when selection is performed in different environmental conditions. Genotype × environment interaction effects involving production systems in a Mediterranean climate and confinement vs. Temperate Oceanic climate and grazing with supplementation, and between two fat plus protein yield level categories within each environment, were at most moderate for the studied traits.     

Cytogenetical studies in the bridge cross Allium cepa× (A. fistulosum×A. roylei)

  Allium fistulosum harbours a number of desirable agronomical traits for the breeding of onions. However exploitation of A. fistulosum for onion breeding via direct sexual hybridization is problematic. Therefore, we examined if a bridge cross, using A. roylei as a bridging species, might provide an alternative. By means of genomic in situ hybridization (GISH) we showed that each of the three parental genomes can be distinguished from the others in interspecific hybrids, suggesting that these genomes contain sufficiently different repetitive DNA families. We succeeded in carrying out multi-colour GISH to metaphase spreads of a first-generation bridge-cross individual [A. cepa× (A. fistulosum×A. roylei], which is composed of three parental genomes. Recombination between the genomes of A. fistulosum and A. roylei took place to a large extent: 7 recombined chromosomes were observed, and it could be shown that the proximal regions of the recombined A. fistulosum/A. roylei chromosomes belonged to the former, whereas the distal parts belonged to the latter. The high percentage of bound bivalent arms in metaphase I of pollen mother cells of a fertile bridge-cross individual suggests the introgression of A. fistulosum genes, mediated by A. roylei, into the genome of A. cepa. However, the presence of univalents reflects decreased pairing and recombination between the three genomes. Pollen fertility and pollen-tube growth of the first-generation bridge-cross individual seem to be sufficient to produce a second generation bridge-cross (A. cepa×first-generation bridge cross) progeny. Received: 27 May 1997 / Accepted: 30 June 1997     

普通小麦×根茎冰草×黑麦三属杂种自交可育性的细胞学机理

普通小麦（ＴｒｉｔｉｃｕｍａｅｔｉｖｕｍＬ．,２ｎ＝６ｘ＝４２;ＡＡＢＢＤＤ）和根茎冰草（ＡｇｒｏｐｙｒｏｎｍｉｃｈｎｏｉＲｅｓｈｅｖ．,２ｎ＝４ｘ＝２８;ＰＰＰＰ）间的Ｆ１杂种（２ｎ＝５ｘ＝３５：ＡＢＤＰＰ）与两个黑麦（ＳｅｃａｌｅｃｅｒｅａｌｅＬ．,２ｎ＝２ｘ＝１４;ＲＲ）品种杂交,产生了自交可育的三属杂种。经细胞学研究表明,这种自交可育性是由于在某些细胞中通过两种方式发生了第一次减数分裂的失败,即单价染色体在赤道板发生分裂和单价染色体在一极的聚集,从而异致了有功能的雌、雄配子的形成。有功能配子的形成受染色体配对频率、基因型和环境状况的影响。冰草属的Ｐ染色体组存在染色体分离的控制基因,从而引起含有冰草属的杂种能够形成有功能的配子且自交可育。