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1.
Identification of quantitative trait loci controlling rice mature seed culturability using chromosomal segment substitution lines 总被引:1,自引:0,他引:1
Lina Zhao Hongju Zhou Liaoxun Lu Li Liu Xianghua Li Yongjun Lin Sibin Yu 《Plant cell reports》2009,28(2):247-256
The genetic transformation efficiency of a rice variety is largely determined by its tissue culturability. Establishment of
a highly efficient tissue-culture system has greatly accelerated the wide spread application of transgenic japonica varieties. However, such process for indica rice was hampered because this type of variety is recalcitrant to in vitro culture. This study aimed to map the quantitative
trait loci (QTLs) for mature seed culturability using a chromosomal segment substitution lines (CSSL) population derived from
a cross between an indica variety “Zhenshan 97B” and a japonica variety “Nipponbare”. The CSSLs consist of 139 lines each containing a single or a few introgression segments, and together
covering the whole “Nipponbare” genome. Every CSSL was tested by culturing on the two medium systems developed for the respective
indica and japonica parental varieties. The performance of culturability was evaluated by four indices: frequency of callus induction (CIF),
callus subculture capability (CSC), frequency of plant regeneration (PRF) and the mean plantlet number per regenerated callus
(MNR). All four traits displayed continuous variation among the CSSLs. With the culture system for japonica rice, three CIF QTLs, three CSC QTLs, three PRF QTLs and three MNR QTLs were detected. With the culture system for indica variety, six CIF QTLs, two CSC QTLs, three PRF QTLs and six MNR QTLs were identified, and these QTLs distributed on nine
rice chromosomes. Two QTLs of CIF and two QTLs of MNR were detected in both the japonica and indica rice culture system. The correlation coefficients of all the four traits varied depending on the culture systems. These results
provide the possibilities of enhancing the culturability of indica rice by marker-assisted breeding with those desirable alleles from the japonica.
Lina Zhao and Hongju Zhou have contributed equally to this work. 相似文献
2.
Asian cultivated rice(Oryza sativa L.),an important cereal crop worldwide,was domesticated from its wild ancestor 8000 years ago.During its long-term cultivation and evolution under diverse agroecological conditions, Asian cultivated rice has differentiated into indica and japonica subspecies.An effective method is required to identify rice germplasm for its indica and japonica features,which is essential in rice genetic improvements.We developed a protocol that combined DNA extraction from a single rice seed and the insertion/deletion(InDel) molecular fingerprint to determine the indica and japonica features of rice germplasm.We analyzed a set of rice germplasm,including 166 Asian rice varieties,two African rice varieties,30 accessions of wild rice species,and 42 weedy rice accessions,using the single-seeded InDel fingerprints(SSIF).The results show that the SSIF method can efficiently determine the indica and japonica features of the rice germplasm.Further analyses revealed significant indica and japonica differentiation in most Asian rice varieties and weedy rice accessions.In contrast,African rice varieties and nearly all the wild rice accessions did not exhibit such differentiation.The pattern of cultivated and wild rice samples illustrated by the SSIF supports our previous hypothesis that indica and japonica differentiation occurred after rice domestication under different agroecological conditions.In addition,the divergent pattern of rice cultivars and weedy rice accessions suggests the possibility of an endoferal origin(from crop)of the weedy rice included in the present study. 相似文献
3.
Kabin?Xie Jianwei?Zhang Yong?Xiang Qi?Feng Bin?Han Zhaohui?Chu Shiping?Wang Qifa?Zhang Lizhong?Xiong
We reported the isolation and identification of 10828 putative full-length cDNAs (FL-cDNA) from an indica rice cultivar, Minghui 63, with the long-term goal to isolate all full-length cDNAs from indica genome. Comparison with the databases showed that 780 of them are new rice cDNAs with no match in japonica cDNA database. Totally, 9078 of the FL-cDNAs contained predicted ORFs matching with japonica FL-cDNAs and 6543 could find homologous proteins with complete ORFs. 53% of the matched FL-cDNAs isolated in this study had
longer 5′UTR than japonica FL-cDNAs. In silico mapping showed that 9776 (90.28%) of the FL-cDNAs had matched genomic sequences in the japonica genome and 10046 (92.78%) had matched genomic sequences in the indica genome. The average nucleotide sequence identity between the two subspecies is 99.2%. A majority of FL-cDNAs (90%) could
be classified with GO (gene ontology) terms based on homology proteins. More than 60% of the new cDNAs isolated in this study
had no homology to the known proteins. This set of FL-cDNAs should be useful for functional genomics and proteomics studies. 相似文献
4.
The advances in genotyping technology provide an opportunity to use genomic tools in crop breeding. As compared to field selections performed in conventional breeding programmes, genomics‐based genotype screen can potentially reduce number of breeding cycles and more precisely integrate target genes for particular traits into an ideal genetic background. We developed a whole‐genome single nucleotide polymorphism (SNP) array, RICE6K, based on Infinium technology, using representative SNPs selected from more than four million SNPs identified from resequencing data of more than 500 rice landraces. RICE6K contains 5102 SNP and insertion–deletion (InDel) markers, about 4500 of which were of high quality in the tested rice lines producing highly repeatable results. Forty‐five functional markers that are located inside 28 characterized genes of important traits can be detected using RICE6K. The SNP markers are evenly distributed on the 12 chromosomes of rice with the average density of 12 SNPs per 1 Mb and can provide information for polymorphisms between indica and japonica subspecies as well as varieties within indica and japonica groups. Application tests of RICE6K showed that the array is suitable for rice germplasm fingerprinting, genotyping bulked segregating pools, seed authenticity check and genetic background selection. These results suggest that RICE6K provides an efficient and reliable genotyping tool for rice genomic breeding. 相似文献
5.
Jain S Jain RK McCouch SR 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2004,109(5):965-977
Genetic relationships among Indian aromatic and quality rice (Oryza sativa) germplasm were assessed using 30 fluorescently labeled rice microsatellite markers. The 69 rice genotypes used in this study included 52 Basmati and other scented/quality rice varieties from different parts of India and 17 indica and japonica varieties that served as controls. A total of 235 alleles were detected at the 30 simple sequence repeat (SSR) loci, 62 (26.4%) of which were present only in Basmati and other scented/quality rice germplasm accessions. The number of alleles per locus ranged from 3 to 22, with an average of 7.8, polymorphism information content (PIC) values ranged from 0.2 to 0.9, with an average of 0.6, and the size range between the smallest and the largest allele for a given microsatellite locus varied between 3 bp and 68 bp. Of the 30 SSR markers, 20 could distinguish traditional Basmati rice varieties, and a single panel of eight markers could be used to differentiate the premium traditional Basmati, cross-bred Basmati, and non-Basmati rice varieties having different commercial value in the marketplace. When estimates of inferred ancestry or similarity coefficients were used to cluster varieties, the high-quality Indian aromatic and quality rice genotypes could be distinguished from both indica and japonica cultivars, and crossbred varieties could be distinguished from traditional Basmati rices. The results indicate that Indian aromatic and quality germplasm is genetically distinct from other groups within O. sativa and is the product of a long, independent pattern of evolution. The data also suggest that there is scope for exploiting the genetic diversity of aromatic/quality rice germplasm available in India for national Basmati rice breeding programs.Electronic Supplementary Material Supplementary material is available for this article at . 相似文献
6.
H. Saruyama N. Shinbashi 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1992,84(7-8):947-951
Summary Proteins extracted from seed embryos of 29 different cultivated rice (Oryza sativa L.) and one wild rice (O. rufipogon Griff.) were compared by two-dimensional gel electrophoresis analysis. Among more than 300 protein spots on the gel we found some interesting variations in ten spots which were individually designated as proteins A-J. Protein E was observed in all indica cultivars but was not found in those of the subspecies japonica. In contrast, protein F was only detected in japonica cultivars. Protein A existed in all japonica cultivars but, with the exception of IR-36, could not be found in other indica cultivars. Therefore, proteins A, E and F can be used as markers for the identification of indica and japonica. Some so-called Javanica cultivars showed the characteristics of japonica subspecies with regard to proteins A and F, while one other cultivar of Javanica expressed a type intermediate between indica and japonica interms of proteins A and E. One feature discriminating between Javanica and japonica cultivars was found in the D, G, and J proteins which were expressed strongly in Javanica cultivars but were scarcely expressed in those of japonica. Expression of subspecies-specific proteins E and F in f1 hybrids was also investigated. 相似文献
7.
C. N. Neeraja S. Malathi E. A. Siddiq 《Journal of plant biochemistry and biotechnology.》2006,15(1):39-41
Subspecific classification of Asian rice (Oryza sativa L) into indica and japonica has always been a subject of interest althrough for rice breeders and geneticists. The present study aims at identifying subspecies specific microsatellite markers in six genotypes, each of indica and japonica using 372 microsatellite primers covering the entire genome. Only 36 primers gave clear polymorphism on 3% agarose gel and these can be used as diagnostic markers for routine and easy identification of the subspecies. 相似文献
8.
9.
Despite extensive studies on cultivated rice, the genetic structure and subdivision of
this crop remain unclear at both global and local scales. Using 84 nuclear simple sequence
repeat markers, we genotyped a panel of 153 global rice cultivars covering all previously
recognized groups and 826 cultivars representing the diversity of Chinese rice germplasm.
On the basis of model-based grouping, neighbour-joining tree and principal coordinate
analysis, we confirmed the widely accepted five major groups of rice cultivars
(indica, aus, aromatic, temperate japonica and
tropical japonica), and demonstrated that rayada rice was unique in
genealogy and should be treated as a new (the sixth) major group of rice germplasm. With
reference to the global classification of rice cultivars, we identified three major groups
(indica, temperate japonica and tropical japonica) in Chinese
rice germplasm and showed that Chinese temperate japonica contained higher
diversity than that of global samples, whereas Chinese indica and tropical
japonica maintained slightly lower diversity than that present in the global
samples. Particularly, we observed that all seasonal, drought-tolerant and endosperm types
occurred within each of three major groups of Chinese cultivars, which does not support
previous claims that seasonal differentiation exists in Indica and
drought-tolerant differentiation is present in Japonica. It is most likely that
differentiation of cultivar types arose multiple times stemming from artificial selection
for adaptation to local environments. 相似文献
10.
Microsatellites are useful tools to study the extent of divergence between two taxonomic groups that show high sequence similarity.
We have compared microsatellite distribution to illustrate genetic variation between the two rice genomes, Oryza sativa L. ssp. indica and Oryza sativa L. ssp. japonica. Microsatellite distribution proved to be non random as certain regions of very high microsatellite density have been identified.
Microsatellite density in the subspecies japonica was computed marginally higher than in the subspecies indica in the genomic regions compared between the two subspecies. Unexpectedly high microsatellite densities were observed in 5′-untranslated
regions of genes. These regions also displayed a clear motif bias. Some of the longest microsatellite repeats were found in
intron sequences. Frequency, as well as motif bias was also noted with respect to the association of microsatellites with
transposable elements. Microsatellite mutability values were exemplarily estimated for 90 loci by aligning the microsatellite
containing regions between the two genomes. Poor rates of finding an orthologue corresponded with high microsatellite mutability
in rice. These insights are likely to play a significant role in selecting microsatellite loci to be used in molecular breeding
and studying evolutionary dynamics of the two subspecies. 相似文献
11.
Analysis of indica- and japonica-specific markers of Oryza sativa and their applications 总被引:1,自引:0,他引:1
Xiao-Jun Dai Yuan-Zhu Yang Liang Zhou Li-Jun Ou Man-Zhong Liang Wen-Jia Li Gong-Ping Kang Liang-Bi Chen 《Plant Systematics and Evolution》2012,298(2):287-296
Asian rice, Oryza sativa L., is one of the most important crop species. Genetic analysis has established that rice consists of several genetically
differentiated variety groups, with two main groups, namely, O. sativa ssp. japonica kata and ssp. indica
kata. To determine the genetic diversity of indica and japonica rice, 45 rice varieties, including domesticated rice and Asia common wild rice (O. rufipogon Griff.), were analyzed using sequence-related amplified polymorphism, target region amplified polymorphism, simple sequence
repeat, and intersimple sequence repeat marker systems. A total of 90 indica- and japonica-specific bands between typical indica and japonica subspecies were identified, which greatly helped in determining whether domesticated rice is of the indica or japonica type, and in analyzing the consanguinity of hybrid rice with japonica, which were bred from indica and japonica crossed offspring. These specific bands were both located in the coding and non-encoding region, and usually connected with
quantitative trait loci. Utilizing the indica-japonica-specific markers, japonica consanguinity was detected in sterile hybrid rice lines. Many indica-japonica-specific bands were found in O. rufipogon. This result supports the multiple-origin model for domesticated rice. Javanica exhibited a greater number of indica-japonica-specific bands, which indicates that it is a subspecies of O. sativa L. 相似文献
12.
R. B. Li Y. Z. Chen Y. P. Wei Ch. Liu Z. F. Ma D. H. Huang Y. X. Zhang W. L. Lu 《Molecular breeding : new strategies in plant improvement》2009,24(2):135-140
Hybrid sterility between indica and japonica subspecies in rice is basically caused by partial abortion of gametes and hybrid fertility could be recovered by a single
wide compatibility (WC) allele. In this study, a typical indica germplasm source of rice, UPRI 95-162, with strong wide compatibility
in cross with japonica rice was studied for location of its WC locus. Bulked segregant analysis was performed and SSRs (simple
sequence repeats) were conducted on a F1 population derived from a three-way cross (UPRI 95-162/T8//Akihikari). The locus was located on chromosome 1 approximately
0.2 cM to SSR markers RM581 on one side and 1.5 cM to RM292 on another. This WC locus, tentatively designated as S-20
n
(t), and its tight linkage markers, RM581 and RM292, would be very useful for efficient marker-assisted selection for breeding
new WC varieties and for map-based cloning of the gene. 相似文献
13.
14.
Geographic distribution and multilocus organization of isozyme variation of rice (Oryza sativa L.) 总被引:5,自引:0,他引:5
Z. Li J. N. Rutger 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2000,101(3):379-387
Genetic organization of isozyme variation in rice (Oryza sativa L.) was investigated based on 17 polymorphic isozyme loci using a sample of 511 accessions of worldwide origin. The genetic
diversity within the species was very high (H=0.36 with 4.82 alleles per locus), as compared with most selfing plant species.
Three diversity centers were detected for isozyme variation including South Asia, China and Southeast Asia. The accessions
were classified into three well-differentiated cultivar groups corresponding to the indica and japonica subspecies, and a new unnamed group. Variation within the cultivar groups accounted for 80% of the total isozyme variation.
Within-country variation accounted for 58% of the total variation while among-region and among-country variation within the
cultivar groups accounted for only 14% and 8% of the total variation. Analyses using log-linear models revealed that pronounced
non-random associations between and among alleles at many unlinked isozyme loci were organized in a non-hierarchical pattern,
and subspecific and macro-geographic differentiation was much more pronounced in multilocus phenotype frequencies than in
allelic frequencies at individual loci. These results suggest that selection on multilocus gene complexes was largely responsible
for the maintenance of the extensive isozyme variation within the species and the indica-japonica differentiation. Our results further suggest the independent domestication of indica and japonica, the dual origins of the indica rice from China and South Asia (India), and the differentiation of the ecotypes ’javanica’ and the ’temperate japonica’ within the japonica subspecies.
Received: 5 August 1999 / Accepted: 13 December 1999 相似文献
15.
Yuanli Zhang Jiao Wang Xiaohui Zhang Jian-Qun Chen Dacheng Tian Sihai Yang 《Journal of molecular evolution》2009,68(4):393-402
Cultivated rice was domesticated from common wild rice. However, little is known about genetic adaptation under domestication.
We investigated the nucleotide variation of both cultivated rice and its wild progenitors at 22 R-gene and 10 non–R-gene loci. A significant regression was observed between wild rice and rice cultivars in their polymorphic levels, particularly
in their nonsynonymous substitutions (θ
a
). Our data also showed that a similar proportion (approximately 60%) of nucleotide variation in wild rice was retained in
cultivated rice in both R-genes and non–R-genes. Interestingly, the slope always was >1 and the intercept always >0 in linear regressions when a cultivar’s polymorphism
was x-axis. The slope and intercept values can provide a basis by which to estimate the founder effect and the strength of
artificial direct selection. A larger founder effect than previously reported and a strong direct-selection effect were shown
in rice genes. In addition, two-directional selection was commonly found in differentiated genes between indica and japonica rice subspecies. This kind of selection may explain the mosaic origins of indica and japonica rice subspecies. Furthermore, in most R-genes, no significant differentiation between cultivated and wild rice was detected. We found evidence for genetic introgression
from wild rice, which may have played an important role during the domestication of rice R-genes.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Yuanli Zhang and Jiao Wang contributed equally to this work. 相似文献
16.
Xiangjin Wei Linglong Liu Junfeng Xu Ling Jiang Wenwei Zhang Jiankang Wang Huqu Zhai Jianmin Wan 《Molecular breeding : new strategies in plant improvement》2010,25(2):287-298
Heading date (HD) is a key trait for the adaptation of rice cultivar to a specific growing region. Here, we report conventional
and marker-assisted breeding strategies using genetic information related to the determination of HD, where the breeding objectives
were to avoid the delayed heading common in indica × japonica hybrids, to increase the efficiency in selecting hybrid rice combinations having a suitable growth duration, and to develop
cultivars with target growth duration by quantitative trait locus (QTL) pyramiding. The allelic constitution at the major
HD loci was determined for a set of 109 leading Chinese rice cultivars by crossing them with HD tester lines. It was shown
that the late heading in indica × japonica hybrids can be overcome by replacing the strong photoperiod-sensitivity allele Se-1
n
with Se-1
e
. A breeding strategy to enable the selection of hybrid combinations with suitable growth duration was proposed, based on
HD genotypic information in rice. Meanwhile, a QTL analysis for HD was conducted over five years based on a recombinant inbred
line population, derived from two parents Asominori (japonica) and IR24 (indica). Four QTLs, located on chromosomes 2, 3, 6, and 8, respectively, could be detected in all five years, indicating they were
stably expressed QTL. According to this QTL information, and taking Asominori as an example, the HD genotypes for improving
the growth duration were designed, and the best breeding selection schemes were determined by use of a genetic breeding simulation
tool. Results obtained in this study demonstrate that genetic information related to HD can make a significant contribution
to rice breeding. 相似文献
17.
Dongling Zhang Hongliang Zhang Meixing Wang Junli Sun Yongwen Qi Fengmei Wang Xinghua Wei Longzhi Han Xiangkun Wang Zichao Li 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2009,119(6):1105-1117
China is one of the largest centers of genetic diversity of Oryza sativa L. in the world. Using a genetically representative primary core collection of 3,024 rice landraces in China, we analyzed
the genetic structure and intraspecific differentiation of O. sativa, and the directional evolution of SSR. The genetic structure was investigated by model-based structure analysis and construction
of neighbor-joining phylogenetic tree. Comparison between genetic structure and predefined populations according to Ting’s
taxonomic system revealed a hierarchical genetic structure: two distinct subspecies, each with three ecotypes and different
numbers of geo-ecogroups within each ecotype. Two subspecies evidently resulted from adaptation to different environments.
The different cropping systems imposed on the subspecies led to further differentiation, but the variation within each subspecies
resulted from different causes. Indica, under tropical-like or lowland-like environments, exhibited clear differentiation among seasonal ecotypes, but not among
soil-watery ecotypes; and japonica showed clear differences between soil water regime ecotypes, but not among seasonal ecotypes. Chinese cultivated rice took
on evident directional evolution in microsatellite allele size at several aspects, such as subspecies and geographical populations.
Japonica has smaller allele sizes than indica, and this may partly be the result of their different domestication times. Allele size was also negatively correlated with
latitude and altitude, and this may be interpreted by different mutation rates, selection pressures, and population size effects
under different environments and cropping systems. 相似文献
18.
H. S. Suh Y. I. Sato H. Morishima 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(3-4):316-321
Weedy rice (Oryza sativa L.) is an important resource for breeding and for studying the evolution of rice. The present study was carried out to identify
the genetic basis of the weedy rices distributed in various countries of the world. One hundred and fifty two strains of weedy
rice collected from Bangladesh, Brazil, Bhutan, China, India, Japan, Korea, Nepal, Thailand and the USA were tested for variations
in six morpho-physiological characteristics and in 14 isozyme loci. Twenty six weedy strains selected from the above materials
were assayed for the Est-10 locus, six RAPD loci of the nuclear genome, and one chloroplast locus. From the results of multivariate analysis based on
the morpho-physiological characteristics and the isozymes, weedy rice strains were classified into indica and japonica types, and each type was further divided into forms resembling cultivated and wild rice. Thus, four groups designated as
I, II, III and IV were identified. Weedy strains of group I (indica-type similar to cultivars) were distributed mostly in temperate countries, group II (indica-type similar to wild rice) in tropical countries, group III (japonica-type similar to cultivars) in Bhutan and Korea, group IV ( japonica-type similar to wild rice) in China and Korea. In group I, classified as indica, several strains showed japonica-specific RAPD markers, while some others had japonica cytoplasm with indica-specific RAPD markers in a heterozygous state at several loci. One weedy strain belonging to group II showed a wild rice-specific
allele at the Est-10 locus. However, in groups III and IV, no variation was ound either for the markers on Est-10 or for the RAPD loci tested. Judging from this study, weedy rice of group I might have originated at least partly from gene
flow between indica and japonica, whereas that of group II most probably originated from gene flow between wild and cultivated indica rice. Weedy rice of group III is thought to have originated from old rice cultivars which had reverted to a weedy form, and
that of group IV from gene flow between japonica cultivars and wild rice having japonica backgrounds.
Received: 2 May 1996 / Accepted: 30 August 1996 相似文献
19.
Li W Zeng R Zhang Z Ding X Zhang G 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2008,116(7):915-922
The partial pollen abortion of hybrids between the indica and japonica subspecies of Asian cultivated rice is one of the major barriers in utilizing intersubspecific heterosis in hybrid rice breeding.
Although a single hybrid pollen sterility locus may have little impact on spikelet fertility, the cumulative effect of several
loci usually leads to a serious decrease in spikelet fertility. Isolating of the genes conferring hybrid pollen sterility
is necessary to understand this phenomenon and to overcome the resulting genetic barrier. In this study, a new locus for F1 pollen sterility, S-d, was identified on the short arm of chromosome 1 by analyzing the genetic effect of substituted segments of the near-isogenic
line E11-5 derived from the japonica variety Taichung 65 (recurrent parent) and the indica variety Dee-geo-woo-gen (donor parent). The S-d locus was first mapped to a 0.8 cM interval between SSR markers PSM46 and PSM80 using a F2 population of 125 individuals. The flanking markers were then used to identify recombinants from a population of 2,160 plants
derived from heterozygotes of the primary F2 population. Simultaneously, additional markers were developed from genomic sequence divergence in this region. Analysis of
the recombinants in the region resulted in the successful mapping of the S-d locus to a 67-kb fragment, containing 17 predicted genes. Positional cloning of this gene will contribute to our understanding
of the molecular basis for partial pollen sterility of intersubspecific F1 hybrids in rice. 相似文献
20.
Quantification of total genomic DNA and selected repetitive sequences reveals concurrent changes in different DNA families in indica and japonica rice 总被引:11,自引:0,他引:11
Ohmido N Kijima K Akiyama Y de Jong JH Fukui K 《Molecular & general genetics : MGG》2000,263(3):388-394
This paper describes a fluorescence in situ hybridization (FISH) analysis of three different repetitive sequence families,
which were mapped to mitotic metaphase chromosomes and extended DNA fibers (EDFs) of the two subspecies of rice (Oryza sativa), indica and japonica (2n=2x=24). The repeat families studied were (1) the tandem repeat sequence A (TrsA), a functionally non-significant repeat; (2)
the [TTTAGGG]n telomere sequence, a non-transcribed, tandemly repeated but functionally significant repeat; and (3) the 5S ribosomal RNA
(5S rDNA). FISH of the TrsA repeat to metaphase chromosomes of indica and japonica cultivars revealed clear signals at the distal ends of twelve and four chromosomes, respectively. As shown in a previous
report, the 17S ribosomal RNA genes (17S rDNA) are located at the nucleolus organizers (NORs) on chromosomes 9 and 10 of the
indica cultivar. However, the japonica rice lacked the rDNA signals on chromosome 10. The size of the 5S rDNA repeat block, which was mapped on the chromosome 11
of both cultivars, was 1.22 times larger in the indica than in the japonica genome. The telomeric repeat arrays at the distal ends of all chromosome arms were on average three times longer in the indica genome than in the japonica genome. Flow cytometric measurements revealed that the nuclear DNA content of indica rice is 9.7% higher than that of japonica rice. Our data suggest that different repetitive sequence families contribute significantly to the variation in genome size
between indica and japonica rice, though to different extents. The increase or decrease in the copy number of several repetitive sequences examined here
may indicate the existence of a directed change in genome size in rice. Possible reasons for this phenomenon of concurrent
evolution of various repeat families are discussed.
Received: 9 August 1999 / Accepted: 29 December 1999 相似文献