According to conventional theory, little genomic changes should occur in homozygous and stable amphiploids of the grass family, particularly those involving polyploid wheat as a parent. In the present study, however, ...According to conventional theory, little genomic changes should occur in homozygous and stable amphiploids of the grass family, particularly those involving polyploid wheat as a parent. In the present study, however, extensive genomic changes were detected in two octoploid partial amphiploids of common wheat (Triticum aestivum L.)_wheatgrass (Agropyron intermedium (Host) P.B.=Elytrigia intermedia (Host) Nevski=Thinopyrum intermedium (Host) Barkworth and Dewey), namely Zhong 3 and Zhong 5, by RFLP analysis using 10 low_copy, wheat chromosome_specific sequences and 33 representative homoeologous group_specific sequences as probes. Genomic changes involved loss of wheat hybridization fragment(s) and/or acquisition of new fragment(s). Uniformity of the RFLP patterns among 5 individual plants taken respectively from Zhong 3 and Zhong 5 in two successive generations, suggested that genomic changes probably had occurred in the early few generations after octoploid amphiploid formation, and remained essentially static thereafter. The highly similar RFLP patterns between Zhong 3 and Zhong 5, which had identical genomic constitution but differed from each other due to involvement of different wheat varieties as parents imply that genomic changes were probably not at random. Possible causes for the extensive and rapid genomic changes in the newly formed plant amphiploids, as well as their implications for polyploid genome evolution and breeding application are discussed.展开更多
As a staple food crop for one-third of the world＇s population, common wheat （Triticum aestivum L., 2n = 6x = 42, AABBDD） plays an important role in humans＇ food security. However, the genetic variation of cultivat...As a staple food crop for one-third of the world＇s population, common wheat （Triticum aestivum L., 2n = 6x = 42, AABBDD） plays an important role in humans＇ food security. However, the genetic variation of cultivated wheat has been dramatically narrowed by genetic erosion under the modem cultivation system, resulting in vulnerability to biotic and abiotic stresses （Jiang et al., 1994; Friebe et al., 1996）. The wild relatives of wheat represent a large reservoir of superior genes, and transferring these alien genes to modem cultivars through chromosome engineering is a successful method of broadening the genetic diversity of wheat （Chen et al., 2003;展开更多
The wild relatives of wheat （Triticum aestivum L.） contain tremendous amounts of potentially useful genes and represent a promising source of genetic diversity for wheat improvement （Bommineni and Jauhar, 1997）. T...The wild relatives of wheat （Triticum aestivum L.） contain tremendous amounts of potentially useful genes and represent a promising source of genetic diversity for wheat improvement （Bommineni and Jauhar, 1997）. Thinopyrum ponticum （Popd.） Barkworth and D. R. Dewey [syn. Agropyron elongatum （Host） P. Beauv., Elytrigia pontica （Podp.） Holub, Lophopy- rum ponticum （Podp.） A. L6ve] （2n = 10x = 70）, has high crossability with various Triticum species. Numerous studies have shown that Th. ponticum carries many potentially valu- able resistance genes against biotic and abiotic stresses （Shannon, 1978; Cox, 1991; Zheng et al., 2014a,b）. Transferring the useful genes from Th. ponticum to common wheat through chromosome engineering had been a successful way to enhance the resistance of wheat to pests and diseases （Sharma et al., 1989; McIntosh, 1991）.展开更多
Partial amphiploids created by crossing common wheat （Triticum aestivum L.） and Thinopyrum ponticum （Podp.） Barkworth ＆ D. R. Dewey are important intermediates in wheat breeding because of their resistance to maj...Partial amphiploids created by crossing common wheat （Triticum aestivum L.） and Thinopyrum ponticum （Podp.） Barkworth ＆ D. R. Dewey are important intermediates in wheat breeding because of their resistance to major wheat diseases. In this study, we examined the chromosome compositions of five Xiaoyan-series wheat-Th, ponticum partial amphiploids （Xiaoyan 68, Xiaoyan 693, Xiaoyan 784, Xiaoyan 7430, and Xiaoyan 7631） using GISH, multicolor-GISH, and multicolor-FISH. We found several chromosome changes in these lines. For example, wheat chromosomes 1B and 2B were added in Xiaoyan 68 and Xiaoyan 7430, respectively, while wheat chromosome 6B was eliminated from Xiaoyan 693 and Xiaoyan 7631. Chromosome rearrangements were also detected in these amphiploids, including an interspecific translocation involving chromosome 4D and some intergenomic translocations, such as A--B and A--D translocations, among wheat genomes. Analysis of the Th. ponticum chromosomes in the amphiploids showed that some lines shared the same alien chromosomes. We also evaluated these partial amphiploids for resistance to nine races of stem rust, including TTKSK （commonly known as Ug99）. Three lines, Xiaoyan 68, Xiaoyan 784, and Xiaoyan 7430, exhibited excellent resistance to all nine races, and could therefore be valuable sources of stem rust resistance in wheat breeding.展开更多
Oryza sativa and Oryza latifolia belong to the AA and CCDD genomes of Oryza, respectively. In this study, amphiploids were obtained from the tube seedlings of O. sativa × O. latifolia F1 hybrids by treatment with...Oryza sativa and Oryza latifolia belong to the AA and CCDD genomes of Oryza, respectively. In this study, amphiploids were obtained from the tube seedlings of O. sativa × O. latifolia F1 hybrids by treatment with colchicine, an agent for chromosome doubling. Subse- quently, amphiploids were investigated using the methods of morphology, genomic in situ hybridization, and molec- ular markers. Amphiploids were characterized by a shorter plant height, larger diameter of stem, longer and wider leaves, darker leaf color, decreased spikelets per panicle and panicle length, and larger spikelets and anthers than the original F1 hybrid. Based on the mitotic metaphase chro- mosome number of the investigated root tips, the somatic chromosome number of the amphiploid is 2n = 72. Additionally, the amphiploid is an allohexaploid, and its genomic constitution is AACCDD by genomic in situ hybridization analysis. Finally, the amphiploids were identified to be true using 37 polymorphic markers at the DNA level.展开更多
Haynaldia villosa possesses a lot of important agronomic traits and has been a powerful gene resource for wheat improvement. However, only several wheat-H, villosa translocation lines have been reported so far. In thi...Haynaldia villosa possesses a lot of important agronomic traits and has been a powerful gene resource for wheat improvement. However, only several wheat-H, villosa translocation lines have been reported so far. In this study, we attempted to develop an efficient method for inducing wheat-H, villosa chromosomal translocations. Triticum durum- Haynaldia villosa amphiploid pollen treated with 1 200 rad ^60Co-y-rays was pollinated to Triticum aestivum cv. ＇Chinese Spring＇. Ninety-eight intergeneric translocated chromosomes between T. durum and H. villosa were detected by genomic in situ hybridization in 44 of 61 M1 plants, indicating a translocation occurrence frequency of 72.1%; much higher than ever reported. There were 26, 62 and 10 translocated chromosomes involving whole arm translocations, terminal translocations, and intercarlary translocations, respectively. Of the total 108 breakage-fusion events, 79 involved interstitial regions and 29 involved centric regions. The ratio of small segment terminal translocations （W.W-V） was much higher than that of large segment terminal translocations （W-V.V）. All of the M1 plants were self-sterile, and their backcross progeny was all obtained with ＇Chinese Spring＇ as pollen donors. Transmission analysis showed that most of the translocations were transmittable. This study provides a new strategy for rapid mass production of wheat-alien chromosomal translocations, especially terminal translocations that will be more significant for wheat improvement.展开更多
: Wide cross and molecular cytogenetic methods were used to transfer the powdery mildew resistance gene from Thinopyron intermedium(Host) Barkworth & DR Dewey to wheat. Among the progeny of crossing common wheat (...: Wide cross and molecular cytogenetic methods were used to transfer the powdery mildew resistance gene from Thinopyron intermedium(Host) Barkworth & DR Dewey to wheat. Among the progeny of crossing common wheat (Triticum aestivum L.) Yannong 15 with Th. intermedium, a partial amphiploid E990256, with resistance to powdery mildew, was developed. It had 56 chromosomes and could form 28 bivalents in pollen mother cells at metaphase I of meiosis. Resistance verification by race 15 at the seedling stage and by mixed strains of Erysiphales gramnis DC. f. sp. tritici Em. Marchal at the adult stage showed it was immune to powdery mildew at both stages. Gene postulation via 21 isolates of E. gramnis f. sp. tritici and 29 differential hosts showed it was nearly immune to all the isolates used, and its resistance pattern was different from all the mildew resistance genes used, which indicated it probably contained a new resistance gene to powdery mildew. Biochemical verification showed it might convey different Th. intermedium chromosomes from those of the wheat- Th. intermedium partial amphiploids Zhong 1–5. Genomic in situ hybridization analysis by using St genomic DNA as the probe showed E990256 contained a recombination genome of St and E.展开更多
In order to develop more wheat-Haynaldia villosa translocations involving different chromosomes and chromosome segments of H. villosa, T. durum-H, villosa amphiploid was irradiated with ^60Co γ-rays at doses of 800, ...In order to develop more wheat-Haynaldia villosa translocations involving different chromosomes and chromosome segments of H. villosa, T. durum-H, villosa amphiploid was irradiated with ^60Co γ-rays at doses of 800, 1,200, and 1,600 rad. Pollen collected from the spikes 1, 2, and 3 days after irradiation were transferred to emasculated spikes of the common wheat cv. ‘Chinese Spring＇. Genomic in situ hybridization was used to identify wheat-H, villosa chromosome translocations in the M1 generation. Transmission of the identified translocation chromosomes was analyzed in the BC1, BC2, and BC3 generations. The results indicated that all three irradiation doses were highly efficient for inducing wheat-alien translocations without affecting the viability of the M1 seeds. Within the range of 800-1,600 rad, both the efficiency of translocation induction and the frequency of interstitial chromosome breakage-fusion increased as the irradiation dosage increased. A higher translocation induction frequency was observed using pollen collected from the spikes 1 day after irradiation over that of 2 or 3 days after irradiation. More than 70% of the translocations detected in the M1 generation were transmitted to the BC1 through the female gametes. All translocations recovered in the BC1 generation were recovered in the following BC2, and BC3 generations. The transmission ability of different translocation types in different genetic backgrounds showed an order of ‘whole-arm translocation 〉 small alien segment translocation 〉 large alien segment translocation＇, through either male or female gametes, In general, the transmission ability through the female gametes was higher than that through the male gametes. By this approach, 14 translocation lines that involved different H. villosa chromosomes have been identified in the BC3 using EST-STS markers, and eight of them were homozygous.展开更多
Hordeum californicum （2n = 2x = 14, HH） is resistant to several wheat diseases and tolerant to lower nitrogen. In this study, a molecular karyotype of H. californicum chromosomes in the Triticum aestivum L. cv. Chin...Hordeum californicum （2n = 2x = 14, HH） is resistant to several wheat diseases and tolerant to lower nitrogen. In this study, a molecular karyotype of H. californicum chromosomes in the Triticum aestivum L. cv. Chinese Spring （CS）-H. californicum amphidiploid （2n = 6x = 56, AABBDDHH） was established. By genomic in situ hybridization （GISH） and multicolor fluorescent in situ hybridization （FISH） using repetitive DNA clones （pTa71, pTa794 and pSc119.2） as probes, the H. californicum chromosomes could be differentiated from each other and from the wheat chromosomes unequivocally. Based on molecular karyotype and marker analyses, 12 wheat--alien chromosome lines, including four disomic addition lines （DAH1, DAH3, DAH5 and DAH6）, five telosomic addition lines （MtH7L, MtHIS, MtH1L, DtH6S and DtH6L）, one multiple addition line involving H. californicum chromosome H2, one disomic substitution line （DSH4） and one translocation line （TH7S/1BL）, were identified from the progenies derived from the crosses of CS-H. californicum amphidiploid with common wheat varieties. A total of 482 EST （expressed sequence tag） or SSR （simple sequence repeat） markers specific for individual H. californicum chromosomes were identified, and 47, 50, 45, 49, 21, 51 and 40 markers were assigned to chromosomes H1, H2, H3, H4, H5, H6 and H7, respectively. According to the chromosome allocation of these markers, chromosomes H2, H3, H4, H5, and H7 of H. californicum have relationship with wheat homoeologous groups 5, 2, 6, 3, and 1, and hence could be designated as 5Hc, 2He, 6Hc, 3Hc and 1Hc, respectively. The chromosomes H1 and H6 were designated as 7Hc and 4Hc, respectively, by referring to SSR markers located on rye chromosomes.展开更多
In vitro variation of B chromosomes was studied by examining the callus cells derived from the immature embryos from a cross of Chinese Spring wheat （Triticum aestivum L.） and Fin 7416 rye （Secale cereale L.） carr...In vitro variation of B chromosomes was studied by examining the callus cells derived from the immature embryos from a cross of Chinese Spring wheat （Triticum aestivum L.） and Fin 7416 rye （Secale cereale L.） carrying two B chromosomes. In 40-d-old callus cells, the numbers of B chromosomes ranged from one to four in 65.6% of the cells observed. The distribution of B chromosome numbers was associated with the ploidy levels of the normal chromosomes （A chromosomes）. The frequency of the cells with high numbers of B chromosomes （i.e., three or four B chromosomes） in the amphiploid cells with 56 A chromosomes was greater than those in the haploid cells with 28 A chromosomes. Although structural changes in the rye A chromosomes were observed, cytological observation and genomic in situ hybridization demonstrated that the rye B chromosomes were conserved in morphological appearance following tissue culture.展开更多
文摘According to conventional theory, little genomic changes should occur in homozygous and stable amphiploids of the grass family, particularly those involving polyploid wheat as a parent. In the present study, however, extensive genomic changes were detected in two octoploid partial amphiploids of common wheat (Triticum aestivum L.)_wheatgrass (Agropyron intermedium (Host) P.B.=Elytrigia intermedia (Host) Nevski=Thinopyrum intermedium (Host) Barkworth and Dewey), namely Zhong 3 and Zhong 5, by RFLP analysis using 10 low_copy, wheat chromosome_specific sequences and 33 representative homoeologous group_specific sequences as probes. Genomic changes involved loss of wheat hybridization fragment(s) and/or acquisition of new fragment(s). Uniformity of the RFLP patterns among 5 individual plants taken respectively from Zhong 3 and Zhong 5 in two successive generations, suggested that genomic changes probably had occurred in the early few generations after octoploid amphiploid formation, and remained essentially static thereafter. The highly similar RFLP patterns between Zhong 3 and Zhong 5, which had identical genomic constitution but differed from each other due to involvement of different wheat varieties as parents imply that genomic changes were probably not at random. Possible causes for the extensive and rapid genomic changes in the newly formed plant amphiploids, as well as their implications for polyploid genome evolution and breeding application are discussed.
基金supported by a grant from the National High Technology Research and Development Program("863" Program) of China(No. 2011AA100103)
文摘As a staple food crop for one-third of the world＇s population, common wheat （Triticum aestivum L., 2n = 6x = 42, AABBDD） plays an important role in humans＇ food security. However, the genetic variation of cultivated wheat has been dramatically narrowed by genetic erosion under the modem cultivation system, resulting in vulnerability to biotic and abiotic stresses （Jiang et al., 1994; Friebe et al., 1996）. The wild relatives of wheat represent a large reservoir of superior genes, and transferring these alien genes to modem cultivars through chromosome engineering is a successful method of broadening the genetic diversity of wheat （Chen et al., 2003;
基金supported by the grants from the National High-Tech Research and Development Program of China (No. 2011AA1001)the National Key Technology R&D Program of China (No. 2013BAD05B01)the National Natural Science Foundation of China (No. 31171539)
文摘The wild relatives of wheat （Triticum aestivum L.） contain tremendous amounts of potentially useful genes and represent a promising source of genetic diversity for wheat improvement （Bommineni and Jauhar, 1997）. Thinopyrum ponticum （Popd.） Barkworth and D. R. Dewey [syn. Agropyron elongatum （Host） P. Beauv., Elytrigia pontica （Podp.） Holub, Lophopy- rum ponticum （Podp.） A. L6ve] （2n = 10x = 70）, has high crossability with various Triticum species. Numerous studies have shown that Th. ponticum carries many potentially valu- able resistance genes against biotic and abiotic stresses （Shannon, 1978; Cox, 1991; Zheng et al., 2014a,b）. Transferring the useful genes from Th. ponticum to common wheat through chromosome engineering had been a successful way to enhance the resistance of wheat to pests and diseases （Sharma et al., 1989; McIntosh, 1991）.
基金supported by the grants from the National Natural Science Foundation of China(No.31171539)the National High-Tech Research and Development Program of China(No.2011AA1001)the National Key Technology R&D Program of China(No.2013BAD05B01)
文摘Partial amphiploids created by crossing common wheat （Triticum aestivum L.） and Thinopyrum ponticum （Podp.） Barkworth ＆ D. R. Dewey are important intermediates in wheat breeding because of their resistance to major wheat diseases. In this study, we examined the chromosome compositions of five Xiaoyan-series wheat-Th, ponticum partial amphiploids （Xiaoyan 68, Xiaoyan 693, Xiaoyan 784, Xiaoyan 7430, and Xiaoyan 7631） using GISH, multicolor-GISH, and multicolor-FISH. We found several chromosome changes in these lines. For example, wheat chromosomes 1B and 2B were added in Xiaoyan 68 and Xiaoyan 7430, respectively, while wheat chromosome 6B was eliminated from Xiaoyan 693 and Xiaoyan 7631. Chromosome rearrangements were also detected in these amphiploids, including an interspecific translocation involving chromosome 4D and some intergenomic translocations, such as A--B and A--D translocations, among wheat genomes. Analysis of the Th. ponticum chromosomes in the amphiploids showed that some lines shared the same alien chromosomes. We also evaluated these partial amphiploids for resistance to nine races of stem rust, including TTKSK （commonly known as Ug99）. Three lines, Xiaoyan 68, Xiaoyan 784, and Xiaoyan 7430, exhibited excellent resistance to all nine races, and could therefore be valuable sources of stem rust resistance in wheat breeding.
基金supported by the National Natural Science Foundation of China (31571624, 31071382)the National Basic Research Program of China (2010CB125904, 2013CBA01405)+1 种基金the key Natural Science Project in University of Jiangsu Province (15KJA210004)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘Oryza sativa and Oryza latifolia belong to the AA and CCDD genomes of Oryza, respectively. In this study, amphiploids were obtained from the tube seedlings of O. sativa × O. latifolia F1 hybrids by treatment with colchicine, an agent for chromosome doubling. Subse- quently, amphiploids were investigated using the methods of morphology, genomic in situ hybridization, and molec- ular markers. Amphiploids were characterized by a shorter plant height, larger diameter of stem, longer and wider leaves, darker leaf color, decreased spikelets per panicle and panicle length, and larger spikelets and anthers than the original F1 hybrid. Based on the mitotic metaphase chro- mosome number of the investigated root tips, the somatic chromosome number of the amphiploid is 2n = 72. Additionally, the amphiploid is an allohexaploid, and its genomic constitution is AACCDD by genomic in situ hybridization analysis. Finally, the amphiploids were identified to be true using 37 polymorphic markers at the DNA level.
基金Supported by the National Natural Science Foundation of China(30270827)the Program for Changjiang Scholars and Innovative Research in Universities(10418).
文摘Haynaldia villosa possesses a lot of important agronomic traits and has been a powerful gene resource for wheat improvement. However, only several wheat-H, villosa translocation lines have been reported so far. In this study, we attempted to develop an efficient method for inducing wheat-H, villosa chromosomal translocations. Triticum durum- Haynaldia villosa amphiploid pollen treated with 1 200 rad ^60Co-y-rays was pollinated to Triticum aestivum cv. ＇Chinese Spring＇. Ninety-eight intergeneric translocated chromosomes between T. durum and H. villosa were detected by genomic in situ hybridization in 44 of 61 M1 plants, indicating a translocation occurrence frequency of 72.1%; much higher than ever reported. There were 26, 62 and 10 translocated chromosomes involving whole arm translocations, terminal translocations, and intercarlary translocations, respectively. Of the total 108 breakage-fusion events, 79 involved interstitial regions and 29 involved centric regions. The ratio of small segment terminal translocations （W.W-V） was much higher than that of large segment terminal translocations （W-V.V）. All of the M1 plants were self-sterile, and their backcross progeny was all obtained with ＇Chinese Spring＇ as pollen donors. Transmission analysis showed that most of the translocations were transmittable. This study provides a new strategy for rapid mass production of wheat-alien chromosomal translocations, especially terminal translocations that will be more significant for wheat improvement.
文摘: Wide cross and molecular cytogenetic methods were used to transfer the powdery mildew resistance gene from Thinopyron intermedium(Host) Barkworth & DR Dewey to wheat. Among the progeny of crossing common wheat (Triticum aestivum L.) Yannong 15 with Th. intermedium, a partial amphiploid E990256, with resistance to powdery mildew, was developed. It had 56 chromosomes and could form 28 bivalents in pollen mother cells at metaphase I of meiosis. Resistance verification by race 15 at the seedling stage and by mixed strains of Erysiphales gramnis DC. f. sp. tritici Em. Marchal at the adult stage showed it was immune to powdery mildew at both stages. Gene postulation via 21 isolates of E. gramnis f. sp. tritici and 29 differential hosts showed it was nearly immune to all the isolates used, and its resistance pattern was different from all the mildew resistance genes used, which indicated it probably contained a new resistance gene to powdery mildew. Biochemical verification showed it might convey different Th. intermedium chromosomes from those of the wheat- Th. intermedium partial amphiploids Zhong 1–5. Genomic in situ hybridization analysis by using St genomic DNA as the probe showed E990256 contained a recombination genome of St and E.
基金supported by the National Natural Science Foundation of China (No.30270827 and 30871519)the High Tech Program of China (No.2006AA100101,2006AA10Z1F6)the Ministry of Educate 111 Project (B08025)
文摘In order to develop more wheat-Haynaldia villosa translocations involving different chromosomes and chromosome segments of H. villosa, T. durum-H, villosa amphiploid was irradiated with ^60Co γ-rays at doses of 800, 1,200, and 1,600 rad. Pollen collected from the spikes 1, 2, and 3 days after irradiation were transferred to emasculated spikes of the common wheat cv. ‘Chinese Spring＇. Genomic in situ hybridization was used to identify wheat-H, villosa chromosome translocations in the M1 generation. Transmission of the identified translocation chromosomes was analyzed in the BC1, BC2, and BC3 generations. The results indicated that all three irradiation doses were highly efficient for inducing wheat-alien translocations without affecting the viability of the M1 seeds. Within the range of 800-1,600 rad, both the efficiency of translocation induction and the frequency of interstitial chromosome breakage-fusion increased as the irradiation dosage increased. A higher translocation induction frequency was observed using pollen collected from the spikes 1 day after irradiation over that of 2 or 3 days after irradiation. More than 70% of the translocations detected in the M1 generation were transmitted to the BC1 through the female gametes. All translocations recovered in the BC1 generation were recovered in the following BC2, and BC3 generations. The transmission ability of different translocation types in different genetic backgrounds showed an order of ‘whole-arm translocation 〉 small alien segment translocation 〉 large alien segment translocation＇, through either male or female gametes, In general, the transmission ability through the female gametes was higher than that through the male gametes. By this approach, 14 translocation lines that involved different H. villosa chromosomes have been identified in the BC3 using EST-STS markers, and eight of them were homozygous.
基金supported by the Technology Support Program of Jiangsu Province (No. BE2012306)the Program of Introducing Talents of Discipline to Universities (No. B08025)+1 种基金the Project No.7 from Science and High-Tech Based Major Program of Agriculture Committee of Shanghai Municipal Administration (No.20127)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘Hordeum californicum （2n = 2x = 14, HH） is resistant to several wheat diseases and tolerant to lower nitrogen. In this study, a molecular karyotype of H. californicum chromosomes in the Triticum aestivum L. cv. Chinese Spring （CS）-H. californicum amphidiploid （2n = 6x = 56, AABBDDHH） was established. By genomic in situ hybridization （GISH） and multicolor fluorescent in situ hybridization （FISH） using repetitive DNA clones （pTa71, pTa794 and pSc119.2） as probes, the H. californicum chromosomes could be differentiated from each other and from the wheat chromosomes unequivocally. Based on molecular karyotype and marker analyses, 12 wheat--alien chromosome lines, including four disomic addition lines （DAH1, DAH3, DAH5 and DAH6）, five telosomic addition lines （MtH7L, MtHIS, MtH1L, DtH6S and DtH6L）, one multiple addition line involving H. californicum chromosome H2, one disomic substitution line （DSH4） and one translocation line （TH7S/1BL）, were identified from the progenies derived from the crosses of CS-H. californicum amphidiploid with common wheat varieties. A total of 482 EST （expressed sequence tag） or SSR （simple sequence repeat） markers specific for individual H. californicum chromosomes were identified, and 47, 50, 45, 49, 21, 51 and 40 markers were assigned to chromosomes H1, H2, H3, H4, H5, H6 and H7, respectively. According to the chromosome allocation of these markers, chromosomes H2, H3, H4, H5, and H7 of H. californicum have relationship with wheat homoeologous groups 5, 2, 6, 3, and 1, and hence could be designated as 5Hc, 2He, 6Hc, 3Hc and 1Hc, respectively. The chromosomes H1 and H6 were designated as 7Hc and 4Hc, respectively, by referring to SSR markers located on rye chromosomes.
文摘In vitro variation of B chromosomes was studied by examining the callus cells derived from the immature embryos from a cross of Chinese Spring wheat （Triticum aestivum L.） and Fin 7416 rye （Secale cereale L.） carrying two B chromosomes. In 40-d-old callus cells, the numbers of B chromosomes ranged from one to four in 65.6% of the cells observed. The distribution of B chromosome numbers was associated with the ploidy levels of the normal chromosomes （A chromosomes）. The frequency of the cells with high numbers of B chromosomes （i.e., three or four B chromosomes） in the amphiploid cells with 56 A chromosomes was greater than those in the haploid cells with 28 A chromosomes. Although structural changes in the rye A chromosomes were observed, cytological observation and genomic in situ hybridization demonstrated that the rye B chromosomes were conserved in morphological appearance following tissue culture.
