A new secondary reciprocal translocation discovered in Chinese wheat

A new wheat-rye secondary reciprocal translocation involving T1RS·7DL and T7DS·1BL was detected by chromosome C-banding and genomic in situ hybridization (GISH). The meiotic configuration analysis combined with C-banding and GISH on F₁ hybrids of this newly discovered translocation with T1RS·1BL and Chinese Spring Dt7DS indicated that the new translocation probably resulted from a secondary reciprocal translocation between the primary translocation T1RS·1BL and 7D in the progenies of Aifeng3//Mengxian201/Neuzucht. On the basis of the cytological analysis of progenies and recombinant inbred lines (RILs) (derived from a cross between T1RS·7DL, T7DS·1BL and T1RS·1BL), the translocation chromosomes T1RS·7DL and T7DS·1BL transmitted readily, and appeared in most of the progenies.     

Die Nutzung der Antherenkulturmethode im Zuchtprozeß von Winterweizen

Anther culture in the breeding process of winter wheat. III. Ability of winter wheat F₁ populations with the two heterozygous 1AL–IAS/1AL–IRS and 1BL–1BS/1BL–IRS chromosome pairs Application of anther culture to four F₁ hybrids between the IBL–IRS (‘Amigo’) and several 1BL–IRS wheat-rye translocation forms yielded 129 green pollen plants in an average embryo induction frequency of 17.6 %. A total of 2632 anthers was inoculated. 25 % and 42 % of the regenerated plants were haploid and spontaneously doubled haploid, and 33 % had abnormal chromosomal structure. After chromosome doubling treatment 87% of all pollen plants set seeds. By means of multiple peroxidases and Giemsa C-banding patterns, the anther culture progeny could be further classified into 16 plants without the short arm of IR-chromosome of rye, 21 IAL–IRS and 50 1BL–IRS translocation lines and into 16 IAL–IRS, IBL–IRS double translocation lines according to the four possible characteristic types of F₂ gametes of the tested F₁ hybrids. Advantages of the haploid technique for the selection of desirable traits and the meaning of the IRS genes in wheat are discussed.     

Transfer of rust resistance from Aegilops ovata into bread wheat (Triticum aestivum L.) and molecular characterisation of resistant derivatives

An interspecific cross was made to transfer leaf rust and stripe rust resistance from an accession of Aegilops ovata (UUMM) to susceptible Triticum aestivum (AABBDD) cv. WL711. The F₁was backcrossed to the recurrent wheat parent, and after two to three backcrosses and selfing, rust resistant progenies were selected. The C-banding study in a uniformly leaf rust and stripe rust resistant derivative showed a substitution of the 5M chromosome of Ae. ovata for 5D of wheat. Analysis of rust resistant derivatives with mapped wheat microsatellite makers confirmed the substitution of 5M for 5D. Some of these derivatives also possessed one or more of the three alien translocations involving 1BL, 2AL and 5BS wheat chromosomes which could not be detected through C-banding. A translocation involving 5DSof wheat and the substituted chromosome 5M of Ae. ovata was also observed in one of the derivatives. Susceptibility of this derivative to leaf rust showed that the leaf rust resistance gene(s) is/are located on short arm of 5M chromosome of Ae. ovata. Though the Ae. ovatasegment translocated to 1BL and 2AL did not seem to possess any rust resistance gene, the alien segment translocated to 5BS may also possess gene(s) for rust resistance. The study demonstrated the usefulness of microsatellite markers in characterisation of interspecific derivatives. This revised version was published online in August 2006 with corrections to the Cover Date.     

C-banded karyotypes and meiotic abnormalities in germplasm derived from interploidy crosses in Avena

C-banded karyotypes of somatic chromosomes and meiotic abnormalities were investigated in four crown rust resistant lines derived from interploidy crosses in Avena.C-banding revealed that line N770-165-2-1 contained a 6C/21translocation while line DCS1789 contained a pair of A. strigosa chromosomes substituted for A. sativachromosome 12. Line JR2-3-3-B contained both the 6C/21 translocation and the pair of substituted A. strigosachromosomes, but line MAM17-4 contained neither. Although meiotic irregularities, including mispositioned bivalents, occurred in all four lines and in their F₁ hybrids with A. sativa, the percentages of normal meiosis ranged from 75.4 to 88.6%. This allowed for stability of line performance and for their use as breeding stocks. This revised version was published online in July 2006 with corrections to the Cover Date.     

Rapid Incorporation of D-genome Chromosomes into A and/or B Genomes of Hexaploid Triticale

Two series of progenies were developed from hybrids between octoploid (AABBDDRR) and tetraploid triticale ((AB)(AB)RR). One arose from the successive selfing of the F₁s, while the second was established after one backcross of the F₁ hybrids with the respective 8 × triticale parent. Altogether, 250 F₃ and BC₁F₂ lines were developed, of which 112 were karyotyped in the F₄/F₅ or in BC₁F₃/BC₁F₄ generations using C-banding and SDS-PAGE. The 112 lines represented 61 different karyotypes, of which 39 appeared to be stabilized, having pairs of homologous wheat chromosomes only, while 22 karyotypes exhibited 1—3 heterologous pairs. The frequency of karyotypically stabilized lines originating from the series with one backcrossing was much higher (79.5 %) than those derived from the successive selfing of the F₁ hybrids (51.7%). Six lines had the pure hexaploid triticale chromosome constitution. The frequency of disomic substitutions of D genome chromosomes for their homoeologous A and/or B genome chromosomes ranged from one to six per line with an average of 1.7. Except for 3B and 6B all possible D(A/B) substitutions were obtained. Chromosomes ID and 3D substituted for their homoeologues with the highest frequency, while the substitution of chromosome 4D for 4A or for 4B was the least frequent. D(R) substitutions were found in eight lines only. A complete set of 6x triticale lines was established in which chromosome ID was present in all possible combinations, i.e. single 1D(1A/1B/1R) disomic substitutions as well as disomic ID addition.     

携带抗白粉病基因Pm21的小麦–簇毛麦小片段易位染色体在不同小麦背景中的传递率及遗传稳定性

抗白粉病基因Pm21来自小麦近缘种簇毛麦。小麦一簇毛麦小片段顶端易位系NAU418(T1AS·1AL-6VS)和小片段中间插入易位系NAU419(T4BS·4BL-6VS-4BL)携带Pm21,高抗白粉病,是小麦抗病育种新种质。为了对其育种利用提供依据,以NAU418和NAU419为亲本分别与来源于不同生态区的郑麦9023等12个小麦品种杂交,杂种F_1再分别与来源于不同生态区的农艺亲本进行正、反回交,研究两种易位染色体在不同小麦背景中的遗传稳定性及其通过雌雄配子的传递规律。DNA分子原位杂交结果表明,在杂种F_1花粉母细胞减数分裂中期Ⅰ(Pollen Mother Cell,PMC MI),两种易位染色体分别可以与对应的小麦染色体配对形成棒状二价体。正、反交结果分析表明,NAU418中的小片段顶端易位染色体T1AS·1AL-6VS通过雌配子和雄配子的传递率分别为8.00%~50.98%和7.89%~45.07%,NAU419中的小片段中间插入易位染色体T4BS·4BL-6VS-4BL通过雌配子和雄配子的传递率分别为29.17%~52.38%和7.69%~47.06%。表明2个易位系中的易位染色体都可以通过雌、雄配子传递,但是其通过雄配子的传递率均显著低于通过雌配子的传递率。     

Detection of wheat-barley translocations by genomic in situ hybridization in derivatives of hybrids multiplied in vitro

Wheat-barley translocations were identified by genomicin situ hybridization (GISH) in backcross progenies originating from in vitro regenerated wheat (Triticum aestivum L. cv. Chinese Spring) × barley (Hordeum vulgare L. cv. Betzes) hybrids. The regenerated hybrids were pollinated with the wheat line Martonvásári 9 kr1. Five translocated wheat-barley chromosomes were recovered among 51 BC₂F₂ progeny from the in vitro regenerated wheat × barley hybrids. All were single breakpoint translocations with the relative positions of the breakpoints ranging from the centromere to about 0.8 of the relative arm length. Of the four translocations with intercalary breakpoints, three were transfers of terminal barley segments to wheat chromosomes; one was a transfer of a terminal wheat segment to a barley chromosome. Because of the absence of diagnostic N-bands, the identity of three barley segments could not be determined; in one translocation the barley chromosome involved had a NOR so it must have been 5H or 6H, and the centric translocation was 4HS.2BL. Following selfing, homozygotes of four translocations were selected. The experiment suggests that in vitro culture conditions are conducive for major genome rearrangements in wheat-barley hybrids. This revised version was published online in July 2006 with corrections to the Cover Date.     

Characterization of wheat-triticale doubled haploid lines by cytological and biochemical markers

Five wheat-triticale doubled haploid (DH) lines— M08, V209, DH220-14-2, DH696-3-4 and M16 —derived from anther culture of F₁s resulting from crosses involving hexaploid or octoploid triticale × hexaploid wheat, were characterized by cytological and biochemical markers. Cytological evidence from genomic in situ hybridization and C-banding indicated that DH lines M08 and V209 (2n= 42) each contained a pair of 1BL/1RS translocation chromosomes. DH220-14-2 (2n= 42) was also a translocated line with two pairs of chromosomes containing small fragments of rye. One of the translocation fragments carried the Sec-1R gene originating from the satellite region of 1RS; the origin of the other one remains unknown. DH696-3-4 (2n= 42) contained a 3D(3R) substitution. In M16 (2n= 44), three pairs of rye chromosomes, 3R, 4R and 6R, were present, 4R as an addition and 3D(3R) and 6D(6R) as substitutions. Biochemical, isozyme and storage protein markers confirmed the cytological conclusions. The advantages of transferring alien chromosomes or chromosome fragments into wheat and creating alien aneuploid lines by anther culture of hybrid F¹s are discussed.     

The derivation of compensating translocations involving homoeologous group 3 chromosomes of wheat and rye

Summary The Sr27 translocation in WRT238 was found to consist of chromosome arms 3RS of rye and 3AS of common wheat. An attempt was made to purposely produce compensating translocations having 3RS and a wheat homoeologous group 3L arm. To achieve this, plants, double monosomic for 3R and a wheat homoeologous group 3 chromosome, were irradiated (7.5 Gy gamma rays) or left untreated before being used to pollinate stem rust susceptible testers. Segregation for stem rust resistance was studied to identify F₂ families with Sr27-carrying translocated chromosomes, these were confirmed by means of C-banding. Compensating translocations 3RS3AL and 3RS3BL) were obtained readily and at similar frequencies from untreated and irradiated plants (respectively, 7.2% and 9.3%). Both translocation types have impaired transmission and segregate approximately 3: 2 (present: absent) in the F₂.     

Isolation of mildew resistant wheat-rye translocation lines from a double substitution line

A powdery mildew resistant double disomic wheat-rye substitution line carrying rye chromosomes 1R and 2R was crossed with normal bread wheats. The F₂ generation was analysed cytologically by C-banding. Wheat-rye chromosome translocations involving both rye chromosomes 1R and 2R were frequent in F₂. Lines with translocations of 1R and 2R were harvested separately. After four generations of selfing and selection for mildew resistance and fertility, fully fertile resistant lines were selected and analysed cytologically. Lines with 1BL/1RS and 2BS/2RL translocations were identified. The resistance on chromosome 1RS could not be shown to be different from control varieties carrying the same rye segment, while the resistance on 2RL is much broader than the earlier known 2RL derived resistance in the line Transec. This revised version was published online in July 2006 with corrections to the Cover Date.     

Karyological characterization of a partial amphiploid,Triticum turgidum L. var. durum × Agropyron intermedium (Host) P.B.

Summary A Giemsa-C-banded karyotype of a partial amphiploid, Triticum turgidum L. var. durum cv. Nodak × Agropyron intermedium (Host) P.B., called MT-2, was analyzed. MT-2 is a winterhardy grasslike octoploid germplasm which survived 5 winters in Montana, and its seed weight is 3 times that of A. intermedium seed. The MT-2 C-banding karyotype shows 6 chromosome pairs each of the A and B wheat genomes with 3A and 4B missing. Chromosomes 1B and 2B are involved in a reciprocal homozygous translocation (T1BS·2BS, T1BL·2BL) which was also confirmed by a nucleolus-associated quadrivalent in an MT-2 × durum wheat backcross. In addition to the wheat chromosomes, MT-2 consistently shows 16 A. intermedium chromosome pairs which are designated from A to P. These chromosomes show C-banding patterns similar to those reported earlier in the literature. A large amount of C-banding polymorphism and structural rearrangements in A. intermedium itself presently make a definite chromosome assignment to the homeologous groups of the Triticeae difficult. The data presented are crucial for further directed manipulation of this germplasm aimed at producing valuable chromosome additions and substitutions in wheat.contribution No. J-2767 from Montana Agric. Exp. Stn.     

Dosage Response of Rye Genes in a Wheat Background

Wheat (Triticum aestivum L.) breeders often utilize alien sources to supply new genetic variation to their breeding programs. However, the alien gene complexes have not always behaved as desired when placed into a wheat background. The introgressed genes of interest may be linked to undesirable genes, expressed at low levels or not at all. The short arm of rye (Secale cereale L.) chromosome one (1RS) contains many valuable genes for wheat improvement. In order to study rye gene response to varying copy number, wheat lines were constructed which contained zero, two or four doses of 1RS. The meiotic behavior of rye chromosome 1R, and wheat/rye translocation chromosomes, 1AL/1RS and 1BL/1RS was studied in the F₁ hybrids between wheat lines carrying 1R or the translocation chromosomes. The IRS arm was transmitted at a very high frequency; 98 % of the F₂ plants had at least one of the chromosomes with a IRS arm. In addition, 44 % of the F₂ plants received at least one copy of the chromosomes from each parent. Analysis of the meiotic behavior of the IRS arm suggested that few euploid wheat gametes were formed. Therefore, most of the pollen must have contained IRS. It is unknown whether the lack of euploid wheat pollen could account for the high transmission frequency of the rye chromosomes. There may have been differential survival of the embryos receiving the rye chromosome as well.     

Identification for H. villosa chromatin in wheat lines using genomic in situ hybridization, C-banding and gliadin electrophoresis techniques

Detection of H. villosa chromosomes in telosomic addition and translocation lines of common wheat was undertaken using genomic in situ hybridization (GISH), C-banding techniques and polyacrylamide gels electrophoresis. The result of GISH on mitotic metaphase cells of the addition line `95039' indicated that the added telochromosomes originated from H. villosa, and it was probably 6VS or 7Vs of H. villosa according to the C-banding pattern. Furthermore, the analysis of gliadin profiles demonstrated that the telochromosome was 6VS. A pair of 1RS/1BL translocation chromosome was also found in `95039'. In addition, mitotic GISH analysis showed that the 6VS/6AL translocation chromosome remained unchanged after being transferred into new wheat background. This revised version was published online in August 2006 with corrections to the Cover Date.     

Location of genes for chlorophyll synthesis on specific arms of chromosomes in Triticum aestivum

Summary An Indian hexaploid wheat var. Pb C591 has been shown to carry gene(s) for chlorophyll synthesis on chromosome 3A (Singh & Joshi, 1979). In the present study cv. Pb.C591, its monosomic 3A and diteocentrics for 3A, 3BL and 3DL of var. Chinese Spring have been used. The F₂ segregation involving crosses between Pb.C591 as male, monosomic line 3A of Pb.C591 (female) and ditelocentrics 3A, 3BL and 3DL of cv. Chinese Spring as male and female respectively has been observed. It has been found that there are two dominant genes regulating chlorophyll synthesis in cv. Chinese Spring. These genes are located on chromosomes arms 3A and 3DS respectively.These chlorophyll synthetic genes must be the same which were postulated by Sears (1956, 1957) as the normal alleles of virescent gene v ₂ (which was located on 3BS) on chromosomes 3A(v ₁) and 3D(V ₃).     

A cytogenetic study of the progenies of hybrids between Brassica napus and Brassica oleracea, Brassica bourgeaui, Brassica cretica and Brassica montana

In this cytogenetic study the progeny of all crosses were investigated in F₁, F₂ and backcross (BC₁) hybrids. Brassica napus and F₁ hybrids between B. napus and B. oleracea, and between B. napus and three wild relatives of B. oleracea (B. bourgeaui, B. cretica and B. montana). Each of the wild relatives has 18 somatic chromosomes. Interspecific F₁ hybrids were obtained through ovary culture mean. These had 28 and 37 chromosomes and their mean pollen fertility was 10.7% and 93.0%, respectively. Many F₂ and BC₁ seeds were harvested from the F₁ hybrids with 37 chromosomes after self‐pollination and open pollination of the F₁ hybrids, and backcrossing with B. napus. Many aneuploids were obtained in the F₂ and BC₁ plants. It is evident from these investigations that the F₁ hybrids may serve as bridge plants to improve B. napus and other Brassica crops.     

Genetic mapping of sequence-specific PCR-based markers on the short arm of the 1BL.1RS wheat-rye translocation

Wheat cultivars carrying the 1BL.1RStranslocation were crossed with newly synthesised octoploid triticale lines involving four rye genotypes having ο-secalin banding patterns different from each other and from that of the 1BL.1RS translocation. Homologous recombination was expected between the short arm of the 1R chromosomes of the rye genotypes and the 1RS arm of the 1BL.1RSwheat/rye translocation. Seven sequence-specific PCR-based markers:Xiag95, RMS13, Bmac0213, GPI, Xpsr960, 5Sand SCM9, and ο-secalinproteins were used to detect recombination events in the BC₁F₂ generation. Segregation analysis demonstrated that a barley SSR marker (Bmac0213) locus was present on the 1RS chromosome arm. Of 834plants tested in four different BC₁F₂ populations, 246individuals were found to carry recombined1BL.1RS translocation chromosomes. Genetic linkage analysis was performed on the eight markers in the four different mapping populations. The physical positions of the markers are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Cytology and pollen grain fertility in creeping bentgrass interspecific and intergeneric hybrids

Creeping bentgrass (Agrostis stolonifera L. or A. palustris Huds.) is a highly outcrossing allotetraploid species. It can form hybrids with a number of other Agrostis species and Polypogon genus. However, cytology and pollen grain fertility of the creeping bentgrass interspecific and intergeneric hybrids are not well known. In this research, chromosome pairing behaviors during meiosis I in F₁ and pollen viability of F₁ hybrids, as well as seed set rate and seed germination rate of backcrosses were studied in hybrids between creeping bentgrass, and other bentgrass species and three species of Polypogon genus. Abnormal chromosome pairing, laggard chromosomes, and premature segregation in F₁ hybrids were found. Pollen viability ranged from 1.6 to 48.5% amongst F₁ hybrids, significantly lower than that of the parents (85.5–94.1%). Some hybrids produced pollens of different sizes within the same anther. Seed set following backcrosses using F₁ hybrids as the male parent and creeping bentgrass as the recurrent parent was significantly lower than their parents. The study of chromosome paring behaviors and progeny fecundity are important in utilizing the alien genes to improve bio-stress and abio-stress resistance, and in assessing the potential transgene risks of creeping bentgrass.     

Chromosomal location of genes for resistance to powdery mildew in common wheat (Triticum aestivum L. em Thell.). 9. Gene MlZec1 from the Triticum dicoccoides-derived wheat line Zecoi-1

The Triticum dicoccoides-derived wheat line Zecoi-1 provides effective protection against powdery mildew. F₃ segregation analysis of Chinese Spring × Zecoi-1 hybrids showed that resistance in line Zecoi-1 is controlled by a single dominant gene. Amplified fragment length polymorphism (AFLP) analysis of bulked segregants from F₃s showing the homozygous resistant and susceptible phenotypes identified eight markers, of which four were associated with the resistance allele in repulsion phase. Following the assignment of these four repulsion phase AFLP markers to wheat chromosome 2B with the aid of Chinese Spring nulli-tetrasomic lines, they were physically mapped in the terminal breakpoint interval 0.89 (2BL-6)–1.00 (telomere) of chromosome 2BL. Genetic and physical mapping of simple sequence repeat markers from the distal half of chromosome 2BL located the wild emmer-derived powdery mildew resistance gene distal of breakpoint 0.89 in deletion line 2BL-6. Based on disease response patterns, genomic origin and chromosomal location the resistance gene in Zecoi-1 is temporarily designated MlZec1.     

Occurrence of numerically unreduced (2n) gametes in Alstroemeria interspecific hybrids and their significance for sexual polyploidisation

The F1 hybrids of seven diploid Alstroemeria species (2n=2x=16) were investigated for the production of numerically unreduced (2n) gametes and their mode of origin. Based on a survey of 17 interspecific hybrid combinations,consisting of 119 genotypes, it was found that the F1 hybrids of Chilean-Brazilian species mostly produced first division restitution (FDR) 2n gametes. These F1 hybrids were self-pollinated in order to obtain F2 seeds, which was an indication that the F1 plants also produced 2neggs simultaneously. All the F2 progeny plants were typical allotetraploids, most of which formed 16 bivalents and a small proportion formed multivalents during metaphase I stages of meiosis. Through genomic in situ hybridisation (GISH) it was proved that multivalent formation in F2plants, derived from A. inodora ×A. pelegrina hybrid, was due to homoeologous recombination but not from reciprocal translocations. In order to test the segregation pattern of the recombinant chromosomes, an F3 population from one genotype, P6C49-6, was investigated. The recombinant chromosomes assorted independently from each other supporting the hypothesis that the segregation of chromosomes in ring quadrivalents did not behave like those in translocation heterozygotes. It was concluded that in allopolyploids of Alstroemeria,bilateral sexual polyploidisation could accomplish genetic recombination by both homoeologous crossing-over as well as through the assortment of chromosomes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Patterns of meiosis in ABDR amphihaploids depend on the specific type of univalent chromosome division

Meiosis in wide F₁ hybrids in the tribe Triticeae is complex and irregular. Despite extensive research, the meiotic pathways in such hybrids remain largely unknown. In this study, the effect of the genotypes of disomic wheat–rye substitution lines on the regulation of meiosis in ABDR amphihaploids was analysed by comparing microsporogenesis and seed set under self pollination in hybrids of normal bread wheat (Triticum aestivum L.) and wheats with single chromosome substitutions 1R(1A), 1Rv(1A), 2R(2D)₁, 2R(2D)₂, 2R(2D)₃, 5R(5D), 5R(5A), 6R(6A) with rye (Secale cereale L.). Three types of meiotic pathways were identified in the hybrids: reductional, equational, and equational+reductional. During the reductional type division, chromosomes randomly moved toward the poles at Anaphase I (AI) and separated sister chromatids at AII. Meiosis ended with tetrad formation, and the resulting plants were sterile ((2R(2D)₁ × R, 2R(2D)₂ × R). In the equational type division, the chromosomes aligned along the equator at Metaphase I and at AI separated into chromatids that moved toward the poles. This meiotic pathway led to dyad formation and partial fertility (especially in hybrids of 1Rv(1A) and 6R(6A)). In the equational+reductional pathway, some chromosomes divided in an equational manner while others were segregated reductionally within the same microsporocyte and this led to formation of tetrads with groups of uncoiled chromosomes. Comparison of the frequencies of each of the three meiotic pathways in different hybrid combinations suggests differences in contributions of individual chromosomes to the control of the entire meiotic process.