Taxonomic studies in Eremopyrum (Poaceae)

Eremopyrum (tribe Triticeae) is revised and 4 species are recognized: E. triticeum (2n = 14), E. orientate (2n = 28), E. distans (2n = 14) and E. bonaepartis (2n = 14,28). A key and maps showing the distribution of the species are presented. The relationships within Eremopyrum , including the origin of the tetraploids, and the relationships between Eremopyrum and other genera of the Triticeae are discussed.     

Two new Tibetan species of Elymus (Poaceae: niticeae) and their genomic relationships

Two Elymus species, E. cacuminus (2n = 4x = 28) and E. retroflexus (2n = 2x = 28). native to western China are described as species new to science. In order to determine genomic constitutions of the two species, intergeneric and interspecific hybridizations were carried out between the two new species and Pseudoroegneria spicata (2n = 2x = 14, SS), and sixteen other Elymus species, fifteen tetraploids (2n = 4x = 28) and one hexaploid (2n = 6x = 42), containing the "SH", "SY", and "SYH" genomes. Chromosome pairing behaviour was studied in the two species and their hybrids. Generally low meiotic pairing was observed in the hybrids with S- and SH-genome species and high pairing in the hybrids with SY- and SYH-genome species. It is concluded from this study that (i) the two new species are strict allotetraploid (2n = 4x = 28) and self-pollinating taxa (inbreeders) in nature; (ii) they contain the "SY" genomes and; (iii) they have close genomic relationships with the SY-genome Elymus species from the same or geographically adjacent areas.     

普通小麦×东方旱麦草属间杂种的产生及无性系的建立

本研究以普通小麦（ＴｒｉｔｉｃｕｍａｅｓｔｉｖｕｍＬ．;２ｎ＝６ｘ＝４２,ＡＡＢＢＤＤ）为母本,以东方旱麦草（Ｅｒｅｍｏｐｙｒｕｍｏｒｉｅｎｔａｌｅ（Ｌ．）Ｊａｕｂ．ｅｔＳｐａｃｈ;２ｎ＝４ｘ＝２８）为父本,首次成功地获得了属间远缘杂种Ｆ１,其平均结实率为０．０８％。利用植物细胞工程技术,对杂种幼胚愈伤组织的诱导、胚性无性系的建立、植株再生、壮苗培养等,最终获得了生长正常的杂种Ｆ１植株。同时,通过对杂种幼胚愈伤组织、根尖细胞的细胞学观察,结果表明该杂种为真杂种,即２ｎ＝５ｘ＝３５（预期染色体数）的杂种细胞占主体;另外,因组培过程中发生了染色体数目的变异,故也有少量２ｎ＝２８－３４染色体数的细胞。以上杂种的获得为将旱麦草优异基因向小麦的转移奠定了基础。     

小麦族鹅观草属三种植物的生物系统学研究

本文研究了禾本科小麦族鹅观草属的3个种:缘毛鹅观草(Roegneria pendulina Neuski 2n=4x=28),纤毛鹅观草(R. ciliaris (Trin.) Nevski 2n=4x=28)和鹅观草(R. kamoji Ohwi 2n=6x=42)及其种间杂种的形态变异和染色体配对行为。各杂种F_1的减数分裂染色体配对数较高,但杂种高度不育。在杂种减数分裂中还观察到一定频率的多价体形成。以上结果充分表明该3种植物享有两个共同的基本染色体组,在S和Y染色体组之间发生过染色体相互易位,缘毛鹅观草的染色体组可拟定为S~PY~P。     

Genomic constitutions of four Chinese endemic Elymus species: E. brevipes, E. yangii, E. anthosachnoides, and E. altissimus (Triticeae, Poaceae).

The objectives of this study were to determine the genomic constitution and to explore the genomic variation within four Chinese endemic Elymus species, i.e., E. brevipes (Keng) L?ve (2n = 4x = 28) and E. yangii B.R. Lu (2n = 4x = 28), E. anthosachnoides (Keng) L?ve (2n = 4x = 28), and E. altissimus (Keng) L?ve (2n = 4x = 28). Intraspecific crosses between different populations of the four Elymus species, as well as interspecific hybridizations among the four target species, and with six analyzer species containing well-known genomes, i.e., E. caninus (L.) L. (2n = 4x = 28, SH), E. sibiricus L. (2n = 4x = 28, SH), E. semicostatus (Lees ex Steud.) Melderis (2n = 4x = 28, SY), E. parviglumis (Keng) L?ve (2n = 4x = 28, SY), E. tsukushiensis Honda (2n = 6x = 42, SHY), and E. himalayanus (Nevski) Tzvelev (2n = 6x = 42, SHY), were achieved through the aid of embryo rescue. Chromosome pairing behaviors were studied in the parental species and their hybrids. Numerical analysis on chromosome pairing was made on the interspecific hybrids. With one exception, each meiotic configuration at metaphase I in the hybrids involving the target taxa and the analyzer species containing the "SH" genomes fit a 2:1:1 model with x-values ranging between 0.91 and 1.00; chromosome pairing in the hybrids involving analyzer parents with the "SY" genomes match a 2:2 model, with x-values between 0.97 and 0.99. All pentaploid hybrids with a genomic formula "SSYYH," except for two crosses having unexpected low c-values, had pairing patterns fitting the 2:2:1 model with x-values varying between 0.96 and 1.00. It is concluded based on hybridization, fertility, and chromosome pairing data that (i) the four target Elymus species are strictly allotetraploid taxa, (ii) they are closely related species, all comprised of the "SY" genomes, (iii) minor genomic structural rearrangements have occurred within the four Elymus species, and (iv) meiotic pairing regulator(s) exists in some of the Elymus taxa studied.     

Chromosome relationships between Lolium and Festuca (Gramineae)

With a view to eclucidating chromosome relationships between Lolium perenne (Lp), L. multiflorum (Lm) and Festuca pratensis (Fp), chromosome pairing in different diploid (2n=14), auto-allotriploid (2n=3x=21), trispecific (2n=3x=21), amphidiploid (2n=4x=28) and auto-allohexaploid (2n=6x=42) hybrids between them was analysed. At all these levels of ploidy there was very good chiasmate pairing between the chromosomes of the three species and, on the whole, there was little evidence of preferential pairing of the chromosomes of a particular species in the triploid, tetraploid and hexaploid hybrids. A critical test for this also came from the synaptic ability of the chromosomes of the single genome with those of the duplicated genome in the auto-allotriploids which formed predominantly trivalents with 2, 3 or even 4 chiasmata. Moreover, the homology between the Lp and Lm chromosomes seems strong enough to pass the discrimination limits of the B-chromosomes which do not suppress homoeologous pairing in the Lp LmLm triploid and LpLm diploid hybrids. — The triploids having two genomes of a Lolium species and one of F. pratensis had some male and female fertility which suggested genetic compatibility of the parental chromosomes resulting, presumably, in compensation at the gametic level. Also, the occurrence of comparable chiasma frequencies in the auto-allotriploids and trispecific hybrids showed that they were not markedly affected whether two doses of one genome and one of the other or all the three different genomes from the three species were present. From the trend of chromosome pairing in all these hybrids it is concluded that there is little structural differentiation between the chromosomes of the three species, no effective isolation barrier to gene-flow between them, and that they are closely related phylogenetically, having possibly evolved from a common progenitor. Taxonomic revision of the two Lolium species is suggested.     

Elymus与普通小麦属间杂种的细胞遗传学研究

本研究以Elymus pendulinus(Nevski)Tzvelev(2n=4x=28,SSYY)、E.shandongenisis B.Salomon(2n=4x=28,SSYY)与普通小麦(Triticum aestivum L.:2n=6x=42,AABBDD)进行了属间远缘杂交。通过对杂种胚的离体培养,两个组合均产生了杂种F_1植株。杂种F_1为多年生,植株生长旺盛;形态上介于亲本种之间而兼具双亲的某些特征;穗状花序发育正常,但均完全不育。两个组合的根尖和花粉母细胞染色体数目为2n-5x=35。通过对杂种减数分裂染色体配对行为的分析,发现其MI染色体的配对水平很低,二价体均为棒状,每细胞的平均染色体交叉数在0.25-0.31之间。这表明E.pendulinus t E.shandongensis 所含的SY染色体组与普通小麦的ABD染色体之间的同源程度很低。由于在E.shandongeasis 及其它具有SY染色体组的Elymus 单倍体中,SY染色体组之间的部份同源染色体配对数均明显高于该杂种中的配对数,这表明存在于普通小麦中的ph基因及其它具类似作用的基因系统能抑制SY染色体组之间的部份同源染色体配对。     

A Biosystematic Study on Hybrids Between Psathyrostachys huashanica and Two Species of Roegneria

Intergeneric crosses were made betweem Psathyrostachys huashanica (2n=14, NN)and two Roegneria species, namely, R. ciliaris (2n=28, SSYY), and R. tsukushiensis (2n=42, SSHHYY). Two combinations of P. huashanica crossed with R. ciliaris and R. tsukushiensis produced adult hybrid plants. Although completely sterile, the hybrid plants developed rather vigorously, and were morphologically intermediate between the two parents.Two spikelets per node in part were observed in hybrids, which evidently came from P. huashanica. The chromosome configurations of R. ciliaris × P. huashanica and R. tsukushiensis × P. huashanica were 20.73 I+0.318 II, 24.80 I+1.578 II+0. 012 III, respectively. Polypolar division was found at anaphase I in meiosis of two hybrids. Abnormal meiosis in two hybrids was observed. The chromosome pairing indicates that there is only a little chromosome homoeology between “N” genome of P. huashanicaand “S”, “Y” or “H” genomes of R. ciliaris and R. tsukushiensis.     

普通小麦×根茎冰草×黑麦三属杂种自交可育性的细胞学机理

普通小麦（ＴｒｉｔｉｃｕｍａｅｔｉｖｕｍＬ．,２ｎ＝６ｘ＝４２;ＡＡＢＢＤＤ）和根茎冰草（ＡｇｒｏｐｙｒｏｎｍｉｃｈｎｏｉＲｅｓｈｅｖ．,２ｎ＝４ｘ＝２８;ＰＰＰＰ）间的Ｆ１杂种（２ｎ＝５ｘ＝３５：ＡＢＤＰＰ）与两个黑麦（ＳｅｃａｌｅｃｅｒｅａｌｅＬ．,２ｎ＝２ｘ＝１４;ＲＲ）品种杂交,产生了自交可育的三属杂种。经细胞学研究表明,这种自交可育性是由于在某些细胞中通过两种方式发生了第一次减数分裂的失败,即单价染色体在赤道板发生分裂和单价染色体在一极的聚集,从而异致了有功能的雌、雄配子的形成。有功能配子的形成受染色体配对频率、基因型和环境状况的影响。冰草属的Ｐ染色体组存在染色体分离的控制基因,从而引起含有冰草属的杂种能够形成有功能的配子且自交可育。     

Intergeneric crosses of Psathyrostachys huashanica with Elymus spp. and cytogenetic studies of the hybrids with E. tsukushiensis (Poaceae, Triticeae)

Intergeneric crosses have been made between Psathyrostachys huashanica (2x= 14, NN) and three Elymus species, namely, E. pendulinus (2n = 4x = 28, SSYY), E. ciliaris (2n = 4x = 28, SSYY), and E. tsukushiensis (2n = 6x = 42, SSHHYY). Three accessions of E. tsukushiensis from different localities crossed with P. huashanica produced adult hybrid plants. Although completely sterile, the hybrid plants developed rather vigorously, and were morphologically intermediate between the two parents. Chromosome configuration of 24.62I + 1.51II + 0.03III per cell characterized meioses of the hybrids, but there existed slight variations among different combinations. These results indicate that there is little or no chromosome homoeology between "N" genome of P. huashanica and "S", "H" or "Y" genomes of E. tsukushiensis.     

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     

Biosystematic studies on Hystrix longearistata from Japan and Hystrix duthiei from China (Poaceae: Triticeae)

Morphological comparison, cytogenetic study and fertility analysis of Hystrix duthiei (2n = 28) from China, Hystrix longearistata (2n= 28) from Japan and their artificial hybrids were carried out. Morphologically H. duthiei was similar to H. longearistata. H. longearistata had longer lemma awn, wider leaf and 2～3 florets per spikelet, while H. duthiei had 1～2 florets per spikelet. These two taxa can be easily crossed. F_l hybrids showed very high degree of bivalent pairing (13～14 bivalents) at the metaphase- I of meiosis. No multivalents were found. The fertility of pollen and seed set of the parents were normal, while the F_l hybrids were of only partial fertility. H. longearistata was closely related to H. duthiei. They should be included in the same species. Because of the differences of their distributions and habitats, some morphological divergency and a little sterility barrier have had appeared between them. It is reasonable to treat Hystrix longearistata as a sub-species of Hystrix duthiei .     

Genomic relationships between species of theElymus semicostatus group andElymus sensu lato (Poaceae)

Meiotic pairing behaviour in 19 interspecificElymus hybrids is reported and discussed. The hybrids were made between four species belonging to theE. semicostatus group of sect.Goulardia, viz.,E. semicostatus, E. abolinii, E. fedtschenkoi, andE. panormitanus (all 2n = 28), andElymus species of seven different sections, viz., sect.Clinelymiopsis:E. caucasicus (2n = 28); sect.Elymus:E. sibiricus (2n = 28); sect.Goulardia:E. caninus (2n = 28),E. trachycaulus (2n = 28), andE. tsukushiensis (2n = 42); sect.Hyalolepis:E. batalinii (2n = 42); sect.Hystrix:E. hystrix (2n = 28); sect.Macrolepis:E. canadensis (2n = 28); and sect.Turczaninovia:E. dahuricus (2n = 42). Chromosomal pairing at meiotic metaphase I indicated that the species of theE. semicostatus group are genomically closer to the tetraploidE. caucasicus and the hexaploid species, regardless of sectional origin, than to the other tetraploid species of sectionGoulardia. Highest meiotic pairing was found in hybrids involvingE. caucasicus, E. tsukushiensis, andE. dahuricus. The presence of pairing regulating genes inE. abolinii is suspected.     

新疆、青海和四川等地区小麦族植物的细胞学观察

本文对采集于新疆、青海和四川等地的小麦族(Triticeae Dumortier)10属、52种、370份种子材料进行了细胞学观察。该地区小麦族各属种的染色体数目变化范围是从2n=14到2n=84,前者主要存在于大麦属(Hordeum)、新麦草属(Psathyrostachys)和黑麦属(Secale),而后者全部集中于赖草属(Leymus)。其中染色体数目为2n=28和2n=42的类型出现的频率很高,大多存在于鹅观草属(Roegneria)和披碱草属(Elymus)。除个别种内存在不同倍性的细胞型外,绝大多数种的染色体数目非常稳定。在所有的样本中均没有观察到具非整倍体和B-染色体的材料。     

Comparative Study of the Ploidy Series Bromus sterilis, B. diandrus and B. rigidus (Poaceae) Based on Chromosome Numbers, Morphology and Isozymes

Abstract: Chromosome numbers, morphological characters and isozymes of seven enzymes were studied to assess relationships between species of the Bromus diandrus-rigidus polyploid complex and the closely related species, B. sterilis. The four different cytotypes detected, 2n = 14, 28, 42 and 56, could be divided into two species: B. sterilis (2n = 14, 28) and B. diandrus (2n = 42, 56) by morphological features and isozymes. The shape of the scar of rachilla segments in the floret proved to be a suitable character for distinguishing the two species, but not the chromosomal races within species. The tetraploid shared homozygous isozyme phenotypes with diploid B. sterilis at all loci, except one, suggesting that it is autopolyploid. No diagnostic isozymes could be found to distinguish between hexa- and octoploid cytotypes in the B. diandrus-rigidus complex.     

A Thinopyrum ponticum and Triticum aestivum hybrid. Electrophoretic patterns of their endogenous phosphorylation, Diphosphonucleoside kinases, DNases and RNases

Endogenous protein phosphorylation, DNase and RNase electrophoretic patterns, and the detection of NDP-kinases by TLC (Thin Layer Chromatography) were performed in Thinopyrum ponticum (2n=10x=70), Triticum aestivum (2n=6x=42), and their hybrid seedlings in order to accomplish intergeneric hybridization. Octoploid intergeneric hybrids (2n=8x=56) were synthesized in less than 50% of the hybrids. The F₁ hybrid plants resembled Th. ponticum with regard to morphological features and were sterile. Hybrid seedlings revealed very low endogenous phosphorylation and very low NDP-kinase activity in comparison to their parents. In addition hybrid seedlings expressed a new nuclease. Received: 29 June 2000 / Accepted: 28 July 2000     

A novel intergeneric hybrid in the Triticeae: Triticum aestivum x Psathyrost achys juncea

Summary Two hybrid embryos of intergeneric origin between Triticum aestivum cv Fukuho (2n=6x=42, AABBDD) and Psathyrostachys juncea (2n=2x=14, NN) were successfully rescued. One hybrid plant had the expected chromosome number of 28 (ABDN), whereas the second plant had 35 chromosomes. The average meiotic chromosome pairing in the 35-chromosome hybrid was 21.87 univalents + 6.38 bivalents + 0.11 trivalents + 0.009 quadrivalents, which indicates that two copies of the N genome were present. Chromosome pairing in the 28-chromosome hybrid was low (1.35 bivalents), and pointed out the lack of homology between the wheat genomes and the P. juncea genome. These new hybrids showed some necrosis and chlorosis, which caused severe floral abortion in the plant that had 35 chromosomes. These problems became gradually less severe after 18 months.Contrib. no. 372     

Synthesis and cytological characterization of trigeneric hybrids of durum wheat with and without Ph1.

Wild grasses in the tribe Triticeae, some in the primary or secondary gene pool of wheat, are excellent reservoirs of genes for superior agronomic traits, including resistance to various diseases. Thus, the diploid wheatgrasses Thinopyrum bessarabicum (Savul. and Rayss) A. Love (2n = 2x = 14; JJ genome) and Lophopyrum elongatum (Host) A. Love (2n = 2x = 14; EE genome) are important sources of genes for disease resistance, e.g., Fusarium head blight resistance that may be transferred to wheat. By crossing fertile amphidiploids (2n = 4x = 28; JJEE) developed from F1 hybrids of the 2 diploid species with appropriate genetic stocks of durum wheat, we synthesized trigeneric hybrids (2n = 4x = 28; ABJE) incorporating both the J and E genomes of the grass species with the durum genomes A and B. Trigeneric hybrids with and without the homoeologous-pairing suppressor gene, Ph1, were produced. In the absence of Ph1, the chances of genetic recombination between chromosomes of the 2 useful grass genomes (JE) and those of the durum genomes (AB) would be enhanced. Meiotic chromosome pairing was studied using both conventional staining and fluorescent genomic in situ hybridization (fl-GISH). As expected, the Ph1-intergeneric hybrids showed low chromosome pairing (23.86% of the complement), whereas the trigenerics with ph1b (49.49%) and those with their chromosome 5B replaced by 5D (49.09%) showed much higher pairing. The absence of Ph1 allowed pairing and, hence, genetic recombination between homoeologous chromosomes. Fl-GISH analysis afforded an excellent tool for studying the specificity of chromosome pairing: wheat with grass, wheat with wheat, or grass with grass. In the trigeneric hybrids that lacked chromosome 5B, and hence lacked the Ph1 gene, the wheat-grass pairing was elevated, i.e., 2.6 chiasmata per cell, a welcome feature from the breeding standpoint. Using Langdon 5D(5B) disomic substitution for making trigeneric hybrids should promote homoeologous pairing between durum and grass chromosomes and hence accelerate alien gene transfer into the durum genomes.     

Genomic in situ hybridization in Avena sativa.

Genomic fluorescent in situ hybridization was employed in the study of the genome organization and evolution of hexaploid oat (Avena sativa L. cv. Sun II, AACCDD, 2n = 6x = 42). Genomic DNAs from two diploid oat species, Avena strigosa (genomic constitution AsAs, 2n = 14) and Avena pilosa (genomic constitution CpCp, 2n = 14), were used as probes in the study. The DNA from A. strigosa labelled 28 of the 42 (2/3) chromosomes of the hexaploid oat, while 14 of the 42 (1/3) chromosomes were labelled with A. pilosa DNA, indicating a close relationship between the A and D genomes. Results also suggested that at least 18 chromosomes (9 pairs) were involved in intergenomic interchanges between the A and C genomes.     

Genomic in situ hybridization differentiates between A/D- and C-genome chromatin and detects intergenomic translocations in polyploid oat species (genus Avena).

The genomic in situ hybridization (GISH) technique was used to discriminate between chromosomes of the C genome and those of the A and A/D genomes in allopolyploid oat species (genus Avena). Total biotinylated DNA from A. strigosa (2n = 2x = 14, AsAs genome) was mixed with sheared, unlabelled total DNA from A. eriantha (2n = 2x = 14, CpCp) at a ratio of 1:200 (labelled to unlabelled). The resulting hybridization pattern consisted of 28 mostly labelled and 14 mostly unlabelled chromosomes in the hexaploids. Attempts to discriminate between chromosomes of the A and D genomes in A. sativa (2n = 6x = 42, AACCDD) were unsuccessful using GISH. At least eight intergenomic translocation segments were detected in A. sativa 'Ogle', several of which were not observed in A. byzantina 'Kanota' (2n = 6x = 42, AACCDD) or in A. sterilis CW 439-2 (2n = 6x = 42, AACCDD). At least five intergenomic translocation segments were observed in A. maroccana CI 8330 'Magna' (2n = 4x = 28, AACC). In both 'Ogle' and 'Magna', positions of most of these translocations matched with C-banding patterns.