A route to de novo domestication of wild allotetraploid rice

1. Download : Download high-res image (314KB)
2. Download : Download full-size image

     

Mutagenesis and phylogenesis of plants

Genetic chromosomes and genome mutations are taken into consideration. For a comparative study of mutagenesis types, data of separate families of seed plants bearing various vital forms of different evolutionary age were used. It was indicated that, in most ancient gymnosperms, the primitive mechanism of genetic mutation has been prevailing. In the process of evolution, chromosome and genome mutagenesis types were added, which enables the creation of new genes without functional disturbances of the ancestral system. Connections between various vital forms and mutagenese types are considered.     

Unraveling the Complex Hybrid Ancestry and Domestication History of Cultivated Strawberry

Cultivated strawberry (Fragaria × ananassa) is one of our youngest domesticates, originating in early eighteenth-century Europe from spontaneous hybrids between wild allo-octoploid species (Fragaria chiloensis and Fragaria virginiana). The improvement of horticultural traits by 300 years of breeding has enabled the global expansion of strawberry production. Here, we describe the genomic history of strawberry domestication from the earliest hybrids to modern cultivars. We observed a significant increase in heterozygosity among interspecific hybrids and a decrease in heterozygosity among domesticated descendants of those hybrids. Selective sweeps were found across the genome in early and modern phases of domestication—59–76% of the selectively swept genes originated in the three less dominant ancestral subgenomes. Contrary to the tenet that genetic diversity is limited in cultivated strawberry, we found that the octoploid species harbor massive allelic diversity and that F. × ananassa harbors as much allelic diversity as either wild founder. We identified 41.8 M subgenome-specific DNA variants among resequenced wild and domesticated individuals. Strikingly, 98% of common alleles and 73% of total alleles were shared between wild and domesticated populations. Moreover, genome-wide estimates of nucleotide diversity were virtually identical in F. chiloensis,F. virginiana, and F. × ananassa (π = 0.0059–0.0060). We found, however, that nucleotide diversity and heterozygosity were significantly lower in modern F. × ananassa populations that have experienced significant genetic gains and have produced numerous agriculturally important cultivars.     

秋水仙碱诱导梨离体叶片再生多倍体

以二倍体梨(Pyrus communis L.) 品种'丰产'试管苗的离体叶片为外植体,研究了秋水仙碱处理对叶片不定梢再生及多倍体诱导率的影响.结果表明:(1)随秋水仙碱处理时间增加,叶片不定梢再生率下降,而多倍体诱导率增加;以0.4%的秋水仙碱溶液处理叶片48 h效果最好,多倍体诱导率为6.1%.(2)流式细胞仪(Flow cytometry)分析鉴定表明,获得的多倍体有三倍体、四倍体和混倍体;多倍体与二倍体的形态特征差异明显,多倍体比二倍体茎粗、节间短,叶形指数小,根粗而且短.     

Can phosphorus limitation contribute to the maintenance of sex? A test of a key assumption

Why sex is so common remains unclear; what is certain is that the predominance of sex despite its profound costs means that it must confer major advantages. Here, we use elemental and nucleic acid assays to evaluate a key element of a novel, integrative hypothesis considering whether sex might be favoured because of differences in body composition between sexuals and asexuals. We found that asexual Potamopyrgus antipodarum, a New Zealand snail, have markedly higher bodily phosphorus and nucleic acid content per unit mass than sexual counterparts. These differences coincide with and are almost certainly linked to the higher ploidy of the asexuals. Our results are the first documented body composition differences between sexual and asexual organisms, and the first detected phenotypic difference between sexual and asexual P. antipodarum, an important natural model system for the study of the maintenance of sex. These findings also verify a central component of our hypothesis that competition between diploid sexuals and polyploid asexuals could be influenced by phosphorus availability.     

Evolutionary history of the Dactylorhiza maculata polyploid complex (Orchidaceae)

Taxonomic complexity may be associated with migration history and polyploidy. We used plastid and nuclear DNA markers to investigate the evolutionary history of the systematically challenging Dactylorhiza maculata polyploid complex. A total of 1833 individuals from 298 populations from throughout Europe were analysed. We found that gene flow was limited between the two major taxa, diploid ssp. fuchsii (including ssp. saccifera) and tetraploid ssp. maculata. A minimum of three autotetraploid lineages were discerned: (1) southern/western ssp. maculata; (2) northern/eastern ssp. maculata; and (3) Central European ssp. fuchsii. The two ssp. maculata lineages, which probably pre‐date the last glaciation, form a contact zone with high genetic diversity in central Scandinavia. Intermediate plastid haplotypes in the contact zone hint at recombination. Central Europe may have been a source area for the postglacial migration for the southern/western lineage of ssp. maculata, as well as for ssp. fuchsii. The northern/eastern lineage of ssp. maculata may have survived the LGM in central Russia west of the Urals. The tetraploid lineage of ssp. fuchsii is indistinguishable from diploid ssp. fuchsii, and is probably of postglacial origin. The Mediterranean region and the Caucasus have not contributed to the northward migration of either ssp. fuchsii or ssp. maculata. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 503–525.     

丰都车前的细胞学研究,兼论它的多倍体起源

对长江三峡库区特有濒危植物丰都车前(Plantago erosa var.fengdouensis)进行了细胞学研究,包括有丝分裂和减数分裂两方面.丰都车前可能为一异源四倍体。其核型公式为2n=4x=24=12m(2sat)+12sm(2sat),属于2A型.极端的环境压力尤其是季节性的水淹可能是此四倍体物种形成的主要原因。对同属内的另一物种车前(P.asiatica)进行了比较观察,确证车前为六倍体。该实验为丰都车前的保育遗传学研究提供了细胞学证据。     

榆叶梅及其部分近缘种的染色体核型分析

采用常规压片法,对5份榆叶梅材料和桃、梅、李、杏4份近缘种材料进行了核型分析,首次报道了4类榆叶梅栽培品种材料的核型。结果表明:‘紫烟’榆叶梅染色体数目为42条,其它榆叶梅材料均为八倍体(2n=8x=64),桃、梅、李、杏均为二倍体(2n=2x=16);核不对称系数为57.68%~63.08%;核型分类为2B和2A型。其中‘紫烟’榆叶梅染色体相对长度组成为:2n=6L+9M2+24M1+3S;近缘种中桃与榆叶梅的核不对称性较接近。