Production and cytogenetic analysis of BC1, BC2, and BC3 progenies of an intergeneric hybrid between Triticum aestivum (L.) Thell. and tetraploid Agropyron cristatum (L.) Gaertn.

Summary Intergeneric hybrids between Triticum aestivum cv Chinese Spring and Agropyron cristatum 4x (2n= 5x=35, ABDPP genomes) with a high level of homoeologous meiotic pairing between the wheat chromosomes were backcrossed 3 times to wheat. Pollination of the F₁ hybrid with Chinese Spring resulted in 22 BC₁ seeds with an average seed set of 1.52%. Five BC₁ plants with 39–41 chromosomes were raised using embryo rescue techniques. Chromosome pairing in the BC₁ was characterized by a high frequency of multivalent associations, but in spite of this there was no evidence of homoeologous pairing between chromosomes of wheat and those of Agropyron. All of the plants were self sterile. The embryo rescue technique was again essential to produce 39 BC₂ plants with chromosome numbers ranging from 37 to 67. The phenomenon of meiotic non-reduction was also observed in the BC₃ progenies. In this generation male and female fertility greatly increased, and meiotic pairing was fairly regular. Some monosomic (2n=43) and double monosomic (2n=44) lines were produced. Analysis of these progenies should permit the extraction of the seven possible wheat-Agropyron disomic addition lines including those with the added chromosomes carrying the genes involved in meiotic non-reduction and in suppression of Ph activity.     

Hybridization between Triticum aestivum L. and Agropyron michnoi Roshev.

Summary Intergeneric hybrids between Triticum aestivum cv Chinese Spring (2n=6x=42, AABBDD) and Agropyron michnoi Roshev. (2n=4x=28, PPPP) were obtained by embryo culture. Their spike characteristics were similar to those of common wheat but, unlike their parents, they were long-awned. The average meiotic chromosome pairing at MI of F₁ hybrids was: 6.39 I +3.75 rodII+8.64 ringII+0.81 III+0.30 IV+0.04 V, the bivalent and multivalent formation of which was much higher than expected from the genomic formulae. It is especially worthwhile to note that the F₁ hybrids were self-fertile, self set being 0.15%, and seeds were easily obtained from the backcross of f₁ plants with hexaploid and tetraploid wheats; here the seed set was more than 20.0%. The polyploid taxa and the position of A. Michnoi in Agropyron are discussed.     

Production,morphology, and cytogenetic analysis of Elymus caninus (Agropyron caninum) x Triticum aestivum F1 hybrids and backcross-1 derivatives

Summary Intergeneric hybrids were produced between common wheat, Triticum aestivum (2n=6x=42, AABBDD) and wheatgrass, Etymus caninus (Agropyron caninum) (2n=4x=28, SSHH) — the first successful report of this cross. Reciprocal crosses and genotypes differed for percent seed set, seed development and F₁ hybrid plant production. With E. caninus as the pollen parent, there was no hybrid seed set. In the reciprocal cross, seed set was 23.1–25.4% depending upon wheat genotype used. Hybrid plants were produced only by rescuing embryos 12–13 days post pollination with cv Chinese Spring as the wheat parent. Kinetin in the medium facilitated embryo germination but inhibited root development and seedling growth. The hybrids were vigorous, self sterile, and intermediate between parents. These had expected chromosome number (2n=5x=35, ABDSH), very little chromosome pairing (0.51 II, 0.04 III) and some secondary associations. The hybrids were successfully backcrossed with wheat. Chromosome number in the BC₁ derivatives varied 54–58 with 56 as the modal class. The BC₁ derivatives showed unusually high number of rod bivalents or reduced pairing of wheat homologues. These were sterile and BC₂ seed was produced using wheat pollen.     

New hybrids of Hordeum parodii with Hordeum vulgare,H. bogdanii,Agropyron caninum and X Triticosecale

Summary Hybrids were produced from crossing Hordeum vulgare, H. bogdanii, Agropyron caninum and × Triticosecale onto H. parodii (6x or 4x). The rates at which hybrids were produced, expressed in terms of plantlet establishment as percent pollinated florets, ranged from 0.47%, (6x H.parodii × 6x × Triticosecale cv. Welsh) to 6.3% (4x H. parodii × 2x H. vulgare cv. Betzes). Based on frequencies of paired configurations at MI, autosyndetic pairing appeared to be promoted by the presence of a Secale cereale genome but suppressed by the genome of H. vulgare.Contribution No. 759 Ottawa Research Station     

Intergeneric hybrids between Triticum crassum and Hordeum vulgare

Summary Intergeneric hybrids between Triticum crassum (2n=6x=42) and Hordeum vulgare cv. Bomi were obtained at a frequency of 15% of pollinated florets. Meiotic chromosome pairing in the hybrids was not different from that observed in a polyhaploid of T. crassum indicating negligible pairing between chromosomes of the two species and secondly that the genome of H. vulgare had no effect on intergenomic pairing in T. crassum.Contribution No. 646 Ottawa Research Station     

Production and cytogenetics of Triticum aestivum L. hybrids with some rhizomatous Agropyron species

Summary Intergeneric hybrids between Triticum aestivum L. and conventional rhizomatous Agropyron species were produced in variable frequencies. They were recovered in high percentage frequencies for T. aestivum cultivars with A. acutum (14.6%), A. intermedium (48.0%), A. pulcherrimum (53.3%), and A. trichophorum (46.6%). The crossability percentages with the highly crossable cultivar Chinese Spring for these Agropyron species accessions were 33.12%, 65.0%, 53.3%, and 65.4%, respectively. Autosyndetic associations of two of their three genomes gave mean meiotic chromosome association data of 17.0 I (univalents) +1.53 II (ring bivalents) + 7.04 II (rod bivalents) +1.43 III (trivalents) +0.05 IV (quadrivalents) +0.01 IV (pentavalents) for A. acutum and of 21.8 I + 1.56 II (rings) +7.22 II (rods) +0.84 III + 0.04 IV for A. intermedium. Chromosome pairing at metaphase I was comparatively lower for A. pulcherrimum (34.4 I + 0.2 II (rings) +3.4 II (rods) +0.14 III) and A. trichophorum (36.7 I + 0.35 II (rings) +2.26 II (rods) + 0.04 III) hybrids with T. aestivum. Hybrids of wheat with A. campestre and A. repens were obtained in low frequency. Direct crossing did not permit T. aestivum/ A. desertorum hybridization. However, by utilizing the 2n=10x=70 A. repens/A. desertorum amphiploid as the pollen source, hybridization with T. aestivum did indeed occur. Aneuploidy was prevalent in this hybrid combination while all other hybrid combinations were apparently normal.     

Meiosis and fertility of F1 hybrids between hexaploid bread wheat and decaploid tall wheatgrass (Thinopyrum ponticum)

As the first step in the transfer of barely yellow dwarf virus resistance and salt tolerance from decaploid tall wheatgrass (Thinopyrum ponticum) into hexaploid bread wheat (Triticum aestivum L.), octoploid intergeneric hybrids (2n = 8x = 56) were synthesized by crossing the tall wheatgrass cultivar Alkar with wheat cvs. Fukuhokomugi (Fuko) and Chinese Spring. (Fuko x Alkar) F₁ hybrids were studied in detail. The F₁ hybrids were perennial and generally resembled the male wheatgrass parent with regard to morphological features and gliadin profile. Most hybrids were euploid with 56 chromosomes and showed high chromosome pairing. On an average, in 6 hybrids 83.6% of the complement showed chiasmatic association, some between wheat and wheatgrass chromosomes. Such a high homoeologous pairing would be obtained if Ph1, the major homoeologous pairing suppressor in wheat, was somehow inactivated. Some of the Fuko x Alkar hybrids had high pollen fertility (18.5–42.0% with a mean of 31.5%) and high seed fertility (3–29 seeds wtih a mean of 12.3 seeds per spike), offering excellent opportunities for their direct backcrossing onto the wheat parent.     

Relationships of Agropyron intermedium chromosomes determined by chromosome pairing and alcohol dehydrogenase isozymes in common wheat background

Summary The relationships of Agropyron intermedium chromosomes in two wheat-Agropyron addition series were determined. Chromosome pairing behaviour revealed that the alien chromosome in lines TAF-2 and L7 of Vilmorin-A. intermedium set are homologous to the alien chromosomes in lines P and C of the Caribo-A. intermedium set respectively. Localization of alcohol dehydrogenase isozyme genes in Vilmorin-Agropyron addition line L4 and in Caribo-Agropyron line O indicated relationships with wheat chromosomes of homoeologous group 4.     

Production and cytogenetics of hybrids of Triticum aestivum x Leymus innovatus

Summary Hybrid plants were obtained between Triticum aestivum (2n=6x=42, AABBDD) and Leymus innovatus (2n=4x=28, JJNN) at a frequency varying from 0.4% to 1.2% of the pollinated florets. Improvement of the embryo culture medium resulted in a higher frequency of embryo rescue. Eight of ten hybrids had the expected chromosome number of 35 (ABDJN). Meiotic analysis indicated that there was no homology between the genomes of the two species. Two hybrids had only 28 chromosomes. Comparison of chromosome pairing between the two types of hybrids suggested that Leymus innovatus carries genes that affect chromosome pairing and behavior. The relatively high occurrence of spontaneous doubling in the meiocytes of these hybrids may indicate that backcrossing of the hybrids to wheat should be possible, although frequent chromosome irregularities observed in the meiocytes of the hybrids may decrease the probability of success of this step, which is essential to the process of gene transfer from L. innovatus to wheat.Contrib. no. 366     

Intergeneric hybrids between Enarthrocarpus lyratus,a wild species,and crop brassicas

Summary Attempts were made to produce intergeneric hybrids between Enarthrocarpus lyratus, a wild species, and several species of crop brassicas: B. campestris, B. nigra, B. oleracea, B. juncea, B. napus and B. Carinata. Hybrids using E. lyratus as female parent were realized by means of embryo rescue in four combinations — E. lyratus x B. campestris, E. lyratus x B. oleracea, E. lyratus x B. napus and E. lyratus x B. carinata. Reciprocal crosses showed strong pre-fertilization barriers and yielded no hybrids except in one combination — B. Juncea x E. Lyratus — in which a single hybrid could be realized. All of the hybrids were multiplied in vitro through the multiplication of axillary shoots. Morphological and cytological studies confirmed hybridity. All hybrids were completely pollen sterile except for E. lyratus x B. carinata, which showed 2% pollen fertility. Attempts to double the chromosome number through the in vitro application of colchicine to axillary meristems of F₁ hybrids were successful in only one hybrid, E. lyratus x B. oleracea. Cytological studies of the hybrids indicated the presence of a partial homology between the genomes of E. lyratus and crop brassicas. Backcross progenies were raised from all of the five F₁ hybrids to develop malesterile alloplasmic lines.     

普通小麦与冰草间杂种的细胞遗传学及其自交可育性

为了进一步研究冰草属（Ａｇｒｏｐｙｒｏｎ Ｇａｅｒｔｎ．）的Ｐ染色体组与小麦染色体组间的遗传关系和评价Ｐ染色体组在属间杂种自交可育性上的遗传效应,获得了普通小麦品种Ｆｕｋｕｈｏ（Ｔｒｉｔｉｃｕｍ ａｅｓｔｉｖｕｍ ｃｖ．Ｆｕｋｕｈｏ,２ｎ＝４２;ＡＡＢＢＤＤ）与３个不同来源的四倍体冰草（Ａ．ｃｒｉｓｔａｔｕｍ＜Ｌ．＞Ｇａｅｒｔｎ．,２ｎ＝２８;ＰＰＰＰ）间的杂种（２ｎ＝３５;ＡＢＤＰＰ）。结果表明     

Inflorescence culture of wheat-Agropyron hybrids: Callus induction,plant regeneration,and potential in overcoming sterility barriers

Segments of young inflorescences of Triticum aestivum cv. Chinese Spring (CS), its F₁ hybrids with Agropyron trachycaulum and A. scirpeum and backcross derivatives with A. yezoense, A. intermedium and A. junceum, and of a A. yezoense x T. aestivum cv. Wichita hybrid were cultured. Different parts of young spikelets of A. trachycaulum x CS F₁ and A. yezoense x Wichita F₁ 's were also cultured. Percent callus induction was lower in wheat than in the wheat-Agropyron hybrids or backcross derivatives. Percent callus induction from different organs in both hybrids was in the descending order of whole spikelet, spikelet without glumes, rachis, and glumes. No plants could be regenerated from calli of wheat and backcross derivatives except those of CS x A. intermedium combination. Callus induction in hybrids varied from 54 to 84% and plant regeneration from 14 to 31%. The regenerants required no vernalization. Variants including one with top-dense spikes and another with elongated spikelets were recovered. Out of eight A. trachycaulm x CS hybrid regenerants, one had anthers and stigma as opposed to neutral flowers of the original hybrid.     

Recovery of normal photosynthesis and respiration in common wheat with Agropyron cytoplasms by telocentric Agropyron chromosomes

Summary Alloplasmic common wheat (Triticum aestivum L. cultivais Penjamo 62 and Siete Cerros 66) with cytoplasms of wheatgrass (Agropyron trichophorum and Ag. glaucum) showed two aberrant phenotypes, i.e., gross reduction in plant vigor and male sterility. Plant vigor and male fertility were restored by cytoplasm-specific telocentric chromosomes (telosomes). Studies on carbon assimilation and consumption and on oxygen evolution and uptake showed that maximum rates of apparent photosynthesis were significantly lower in the alloplasmic lines than in their corresponding euplasmic lines and that the telosomes restored a normal level of photosynthesis. The decreased apparent photosynthetic rates in the alloplasmic lines were shown to be not due to decreased rates of true photosynthesis but to increased rates of dark respiration in the green leaves. In contrast, dark respiration in the roots was significantly low in the alloplasmic lines. The alloplasmic lines also showed decreased rates of respiratory consumption of new photosynthates. These results suggest that growth depression and male sterility in the alloplasmic lines are related to aberrant mitochondrial function, which is compensated for by cytoplasm-specific telosomes.     

Chromosome substitutions of Triticum timopheevii in common wheat and some observations on the evolution of polyploid wheat species

Whether the two tetraploid wheat species, the well known Triticum turgidum L. (macaroni wheat, AABB genomes) and the obscure T. timopheevii Zhuk. (A^tA^tGG), have monophyletic or diphyletic origin from the same or different diploid species presents an interesting evolutionary problem. Moreover, T. timopheevii and its wild form T. araraticum are an important genetic resource for macaroni and bread-wheat improvement. To study these objectives, the substitution and genetic compensation abilities of individual T. timopheevii chromosomes for missing chromosomes of T. aestivum Chinese Spring (AABBDD) were analyzed. Chinese Spring aneuploids (nullisomic-tetrasomics) were crossed with a T. timopheevii x Aegilops tauschii amphiploid to isolate T. timopheevii chromosomes in a monosomic condition. The F₁ hybrids were backcrossed one to four times to Chinese Spring aneuploids without selection for the T. timopheevii chromosome of interest. While spontaneous substitutions involving all A^t- and G-genome chromosomes were identified, the targeted T. timopheevii chromosome was not always recovered. Lines with spontaneous substitutions from T. timopheevii were chosen for further backcrossing. Six T. timopheevii chromosome substitutions were isolated: 6A^t (6A), 2G (2B), 3G (3B), 4G (4B), 5G (5B) and 6G (6B). The substitution lines had normal morphology and fertility. The 6A^t of T. timopheevii was involved in a translocation with chromosome 1G, resulting in the transfer of the group-1 gliadin locus to 6A^t. Chromosome 2G substituted for 2B at a frequency higher than expected and may carry putative homoeoalleles of gametocidal genes present on group-2 chromosomes of several alien species. Our data indicate a common origin for tetraploid wheat species, but from separate hybridization events because of the presence of a different spectrum of intergenomic translocations.     

Cytogenetical studies on artificial hybrids amongElymus sibiricus,E. dahuricus andAgropyron tsukushiense in the tribe Triticeae,Gramineae

To explore the cytogenetical relationships ofElymus andAgropyron of the tribe Triticeae, Gramineae, two species of AsiaticElymus, E. sibiricus (2n=28) andE. dahuricus (2n=42), and a JapaneseAgropyron, A. tsukushiense (2n=42) were crossed. Pentaploid and hexaploid F₁ hybrids were vigorous. All pollen grains were aborted and none of the hybrids produced seed. For the crossE. sibiricus × A. tsukushiense, the average chromosome pairing per cell at the MI of the PMCs in the F₁ was 16.38 univalents, 8.93 bivalents, 0.25 trivalents and 0.01 quadrivalents; for the crossE. dahuricus × A. tsukushiense, it was 4.41 univalents, 17.67 bivalents, 0.32 trivalents, 0.28 quadrivalents and 0.04 quinquevalents; and for the crossE. dahuricus × E. sibiricus, it was 17.11 univalents, 8.74 bivalents, 0.04 trivalents and 0.07 quadrivalents. From the present results, it is concluded thatE. sibiricus contains one genome andE. dahuricus contains two genomes, which are homologous to those ofA. tsukushiense, and that the third genome ofE. dahuricus might be partially homologous to the remaining genome ofA. tsukushiense. This conclusion is also supported by the cytogenetical analysis ofE. dahuricus × E. sibiricus. Contribution No. 27 from the Plant Germ-plasm Institute, Faculty of Agriculture, Kyoto University, Kyoto, Japan.     

Production of wide hybrids and backcross progenies between Diplotaxis erucoides and crop brassicas

Intergeneric hybrids were produced between D. erucoides (), a wild species, and four cultivated species of Brassica, B. campestris, B. juncea, B. napus and B. oleracea, through embryo rescue. The hybrid nature of these plants was confirmed through morphological and cytological studies. Backcross pollinations with the pollen of the respective cultivars yielded BC progenies in the hybrids D. erucoides x B. juncea and D. erucoides x B. napus but not in D. erucoides x B. campestris and D. erucoides x B. oleracea. The hybrid D. erucoides x B. campestris was also used as a bridge species and crossed with B. juncea to raise the hybrid and backcross progenies. F₂ progenies were more amenable than f₁ hybrids for raising backcross progenies. Although D. erucoides is considered to be a close relative of B. campestris and B. oleracea, incompatibility barriers of this species with different cultivars do not reflect this relationship.     

The effect of B-chromosomes of rye on the chromosome association in F1 hybrids Triticum aestivum x Secale cereale in the absence of chromosomes 5B or 5D

Summary T. aestivum var. Chinese Spring (monosomic 5B and 5D, respectively) was crossed with S. cereale (with and without B-chromosomes). The resulting nullisomic 5B hybrids exhibited a high degree of chromosome association both at 20°C and 10°C. The presence of B-chromosomes reduced association slightly whether 5B was present or not.In nullisomic 5D hybrids B-chromosomes of rye raise chromosome association at 20°C when compared to hybrids with 5D, with as well as without, B's. At 10°C, due to the absence of the Ltp gene on 5D, chromosome association in nullisomic 5D hybrids is low, and no effects of rye B-chromosomes is detectable.The hypothesis that B-chromosomes of rye carry (an) asynaptic gene(s) decreasing effective pairing, and (an) independent post-synaptic gene(s) increasing chiasma frequency on effective pairing sites, is presented.The work was supported by a fellowship of the Gulbenkian Foundation and partly carried out while the author was at the Department of Genetics, Agricultural University, Wageningen, the Netherlands     

High crossability of wild barley (Hordeum spontaneum C. Koch) with bread wheat and the differential elimination of barley chromosomes in the hybrids

Four bread wheat (Triticum aestivum L.) cultivars, Aobakomugi, Chinese Spring, Norin 61 and Shinchunaga, were pollinated with five barley lines/cultivars consisting of three cultivated barley (Hordeum vulgare L.) lines, Betzes, Kinai 5 and OHL089, and two wild barley (Hordeum spontaneum C. Koch) lines, OUH602 and OUH324. Crossability, expressed as the percentage of embryo formation, varied from 0 to 55.4% among the cross combinations. The two wild barley lines generally had a higher crossability than the previously reported best pollinator, Betzes, and some Japanese wheat cultivars were better as the female parent than Chinese Spring. Ninety four hybrid plants were obtained from 250 embryos cultured, and their somatic chromosome numbers ranged from 21 to 36. Eighteen plants were mosaic in chromosome number. Twenty one-chromosome plants appeared most frequently (45.7%) followed by 28-chromosome plants (14.9%). C-banding analysis revealed that elimination of barley chromosomes was mainly responsible for the occurrence of aneuploid plants. In hypoploids derived from Betzes-crosses, chromosome 5 was preferentially eliminated as previously reported, while in hypoploids derived from OUH602-crosses, chromosome 4 was preferentially eliminated. The wild barley line OUH602 may be a useful parent for producing a new wheat-barley addition set because of its high crossability with wheat and a different pattern of chromosome elimination.     

Genetic analysis of photosynthetic variation in hexaploid and tetraploid wheat and their interspecific hybrids

Intra- and inter-specific variation in CO₂ assimilation rate (A) in Triticum spp. is well documented for reproductive growth stages. Research was conducted to characterize early vegetative photosynthetic variation in a diverse set of cultivated hexaploid wheat (T. aestivum L.) germplasm and in wild tetraploid (T. dicoccoides Korn) and hexaploid x tetraploid populations. Choice of hexaploid genotypes was based on maximum genetic distance between cultivars within the HRW and SRW wheat classes of the USA. The tetraploid material was produced by hybridizing two accessions of T. dicoccoides previously shown to differ widely in A and A/Chl but with similar leaf morphology. Genetic variability in the HRW and SRW gene pools was attributed to more recently developed descendent lines and unrelated lines rather than parental lines. Phenotypic distributions for A, stomatal conductance (gs), and internal CO₂ concentration (Ci) in the F₂ tetraploid population were continuous and showed transgressive segregation, reflecting quantitative inheritance with intermediate heritability. Variability in A was not associated with chlorophyll content or CO₂ supply to the mesophyll measured as Ci. Genetic variability in A was also observed in the interspecific backcross population, 2*TAM W-101/PI 428109, thereby providing a germplasm pool to select for high A while restoring the D genome of hexaploid wheat. These results suggest that genetic improvement of vegetative assimilation rate is feasible in hexaploid wheat via homologous transfer from an alien source.Abbreviations HRW hard red winter - LA leaf area - r_G genotypic correlation - r_P phenotypic correlation - SRW soft red winter     

Isolated wheat microspore culture

The use of doubled haploid plants in a wheat breeding program requires an efficient haploid production system. While the techniques for producing doubled haploids from anther culture are well established, those for isolated microspores are complicated and inefficient. Four methods of isolating microspores from anthers (blending, stirring, macerating, and floating) were compared. Isolated microspores were washed and cultured in liquid medium. The effects of pre-isolation mannitol conditioning, cell density, culture dilution, and sucrose centrifugation on microspore viability were evaluated. Isolation by blending gave the highest initial microspore viability (75%). Mannitol conditioning and purification by sucrose centrifugation had a detrimental effect on initial viability. An initial microspore density of 2 × 10⁵ microspores per ml was necessary for continued microspore viability. One hundred and nine haploid or spontancously doubled haploid plants were regenerated from microspores isolated without mannitol conditioning using the blending method. Based on this research, blender isolation with an initial density of 2 × 10⁵ microspores per ml is recommended for isolated microspore culture.Abbreviations LSmean least square mean - MES 2-N-morpholinoethane sulfonic acid - 2,4-d 2,4-dichlorophenoxyacetic acid - NAA -naphtaleneacetic acid