Spontaneous haploids in durum wheat: their cytogenetic characterization

Summary Durum or macaroni wheat (Triticum turgidum L., 2n = 4x = 28; AABB genomes) arose as a natural hybrid between two wild species, Aegilops speltoides Tausch (2n = 2x = 14; BB genome) and Triticum urartu Tumanian (2n = 2x = 14; AA genome). The two progenitors hybridized in nature about half a million years ago and gave rise to tetraploid wheat, presumably in one step as a result of functioning of unreduced gametes in their hybrid BA (amphihaploid). It is easily possible to go back on the evolutionary scale and obtain durum haploids BA, and then regenerate tetraploid durum plants from them. Interestingly, such a reversion to haploidy does occur in nature as well, although at a very low frequency. This article reports on the occurrence of two spontaneous durum haploids and describes their chromosomal characteristics. The haploids (euhaploids, to be precise) had 14 somatic chromosomes, which, on fluorescent genomic in situ hybridization (fl-GISH), could be distinguished as 7 A-genome and 7 B-genome chromosomes. At meiosis, only 2.3 and 2.7% of the chromosomes paired in the two haploids, because of the presence of the homoeologous pairing-suppressor gene, Ph1. The Ph1-induced lack of pairing is a prerequisite for chromosome doubling through the formation of unreduced gametes that give rise to tetraploid durum wheats.Mention of trade names or commercial products in this publication is solely to provide specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.     

Transfer of the Glu-D1 Gene from Chromosome 1D of Breadwheat to Chromosome 1R in Hexaploid Triticale

The use of hexaploid triticale as a crop for human consumption has been limited by its inferior bread-making quality. To ameliorate this problem, a segment of chromosome ID of breadwheat with the Glu-D1d allele encoding for high molecular weight glutenin subunits 5 7plus; 10 was translocated to chromosome 1R of the hexaploid triticale ‘Rhino’ through a combination of a centric break-fusion translocation followed by 5D(5B)-induced homoeologous pairing. The resulting recombinant chromosome 1R has a small interstitial segment of ID with the Glu-D1d allele. The maximum physical length of the translocated segment is estimated at about 16.5 % of 1DL. Frequency of translocations involving the long arms of homoeologous group-1 chromosomes in the analyzed progeny suggested that homoeologous recombination in triticale was substantially higher than that previously reported in hexaploid wheat.     

Genetic affinity between two chemotypes of clary sage (Salvia sclarea L.)

Summary A new and unique chemotype of clary sage, Salvia sclarea L., was identified recently in wild populations of this species in the northern part of Israel. This chemotype was crossed to a cultivated form of clary sage of Russian origin which represents the standard chemotype of the species. The two chemotypes were easily intercrossed with one another and in both cross directions. The hybrids were vigorous but totally sterile despite apparent normal chromosome pairing at meiosis and regular segregation at Anaphase I. It seems, therefore, that the genetic diversity of the Israeli material can not be exploited to enrich the gene pool of clary sage. Further study is needed to determine the geographic distribution of the new chemotype and whether or not it deserves different taxonomic rank.     

Homeology Between the Chromosomes of Avena macrostachya and the Avena C Genome

To gain more information about the widely unknown genome constitution of the taxonomically and agronomically interesting wild oat Avena macrostachya, this tetraploid species was crossed (as the pollinator) with several diploid Avena species. Hybridization failed with A. strigosa (A_s A_s), A. hirtula (A_s A_s), and A. longiglumis (A₁ A₁), but succeeded with A. atlantica (A_s A_s), A. prostrata (A_p A_p), and A. pilosa (C_p C_p). The output of hybrids and the vitality of the F: plants were highest in the combination A. pilosa×A. macrostachya. Hybrids from this cross relatively frequently showed trivalents at metaphase I as compared to the nearly consistent formation of seven univalents and seven bivalents in hybrids with the A genome species A. atlantica and A. prostrata. Altogether, the results confirm an auto-ploid origin of A. macrostachya and demonstrate that among the two known basic genomes A and C of the genus Avena only the latter exhibits considerable homeology to the A. macrostachya genome.     

(苏丹草×拟高梁)种间杂种主要特征特性及细胞学分析

利用人工去雄、多次授粉法获得(苏丹草×拟高梁)F_1种间杂种。苏丹草(2n=20)与拟高梁(2n=20)杂交结实率及杂种发芽率均较低,正反交存在较大的差异.F_1杂种形态和饲草品质介于双亲之间,雌雄配子均具有一定的孕性。杂种对叶斑病表现较强的抗性。F_1花粉母细胞减数分裂染色体配对较为正常,98.8%的细胞均形成10个二价体,无多价体出现,具单价体的细胞频率仅为1.2%,表明双亲在细胞学上具有较高的同源性。F_2和 BC_1代植株形态、结实率和抗病性等差异较大,分离出饲草品质较好、落粒性弱、种子产量高和抗病性较强的中间型植株,这些后代可能对苏丹草抗病育种或拟高粱品质育种有重要的利用价值。     

Comparative cytological study of Solanum aethiopicum Gilo group,Solanum aethiopicum Shum group and Solanum anguivi

Summary Comparative cytological studies were carried out on Gilo and Shum cultivar groups of Solanum aethiopicum (scarlet eggplant) and their ancestor-Solanum anguivi, in order to elucidate the evolutionary relationships between them. Results indicated preferential pairing of chromosomes in S. anguivi and non-preferential pairing of chromosomes in Gilo and Shum cultivar groups of S. aethiopicum during early stages of meiosis. The low degree of pairing in Gilo and Shum cultivar groups of S. aethiopicum and higher percentage of chromosomal abnormalities (12.50 and 10.58% respectively showed cases of translocation heterozygotes and suggest that the two taxa have hybrid origin. Conversely, the high degree of pairing and very low percentage of chromosomal abnormalities (2.50%) tend to suggest that S. anguivi is more ancient than either the Gilo and Shum cultivar groups of S. aethiopicum. It had already been proved that the Gilo and Shum cultivar groups of S. aethiopicum together with the Kumba and Aculeatum groups originated from S. anguivi (Lester & Niakan, 1986). Also studies on external morphology and cytological studies have shown the Gilo cultivar group to be more complex morphologically and having higher percentage of chromosomal aberrations (12.50% as against 10.58% observed in Shum cultivar group). It is suggested that the Gilo cultivar group might have evolved from the Shum cultivar group through hybridization and selection, while the S. anguivi was already stabilized as their ancestor.     

Cytogenetic Analysis of the Primary Amphidiploid Derived from Interspecific Hybridization in Cucumis and Its Selfed Progenies

Studies on the reproduction and cytogenetic characterization of a primary amphidiploid Cucumis species C. hytivus Chen and Kirkbride (2n = 4x = 38) indicated that a more comprehensive cytogenetic analysis of this species and its first selfed progeny would increase its potential utility in cucumber improvement. With tendrils used as source materials for mitotic analysis, chromosome numbers in all selfed progenies were 2n = 38, confirming chromosomal stability in this synthetic amphidiploid species. Detailed meiotic processes were described by comparing the primary and the selfed amphidiploids.Meiotic abnormalities, such as chromosome lagging, unequal separation, chromosome multi-polarization and polyads were observed frequently in all amphidiploid plants except for the selfed no.8, in which meiosis was arrested prior to metaphase I. Generally, the frequency of multivalents was higher and the configurations were more complex in the selfed progenies, demonstrating a more extensive genetic exchange between cucumber and C. hystrix Chakr. Genome separation between cucumber and C. hystrix was observed through prophase ! to anaphase I in both generations of the amphidiploids. Consequently, in addition to n = 19, a new gamete with n = 7 was produced, which was confirmed by the chromosome counts 2n = 14 in the backcrossing progenies from cucumber × amphidiploid mating. Fertility varied among the selfed amphidiploid plants. The selfed plant no. 1 was found to have an improved fertility (e.g., pollen staining ability 40.8% and 25.6 seeds per fruit) and then was used as source germplasm in further introgression and gene exchange experiments.     

B染色体组对芸苔属部分同源染色体组A．B．C之间染色体配对关系的影响

观察了芸苔属４个种（黑芥、甘蓝型油菜、芥菜型油菜和埃塞俄比亚芥）间杂种Ｆ＿１花粉母细胞减数分裂中期Ｉ染色体的配对行为，结果表明，芥菜型油菜×黑芥、埃塞俄比亚芥×黑芥、芥菜型油菜×埃塞俄比亚芥、芥菜型油菜×甘蓝型油菜和甘蓝型油菜×埃塞俄比亚芥Ｆ１杂种分别平均表现出９．７７Ｉ＋８．０３Ⅱ＋０．０３Ⅲ、８．８２Ｉ＋８．０２Ⅱ＋０．０５２Ⅲ，２．５６Ｉ＋１４．９８Ⅱ＋０．３９Ⅲ＋０．３３Ⅳ（Ⅴ），１４．１７Ｉ＋１１．１５Ⅱ＋０．１３３Ⅲ＋０．０２７Ⅳ和１５．４２Ｉ＋１０．１４Ⅱ＋０．０８５Ⅲ＋０．０１４Ⅳ的构型。由此说明，在芸苔属Ａ、Ｂ和Ｃ染色体组之间，Ａ与Ｃ的同源性大于Ａ与Ｂ或Ｂ与Ｃ的同源性；同时，Ｂ染色体组对Ａ与Ｂ、Ａ与Ｃ及Ｂ与Ｃ之间的部分同源染色体配对关系没有影响。     

Taxonomic relationships and interspecific hybridization in the genus Lolium (grasses)

Phylogenetic trees of the 8 species of the genus Lolium and of Festuca pratensis have been derived from frequency data at 13 isozyme loci using different distance algorithms. The best tree was obtained by the distance-Wagner method with the Cavalli-Sforza and Edwards chord distance. This tree appears robust when tested by bootstrap resampling of loci. This confirmed previous knowledge on species relationships in the genus Lolium, with supplementary data on the taxonomic position of the less studied L. persicum and L. canariense. Attempts were made to hybridize 4 Lolium species and F. pratensis. True interspecific hybrids, as confirmed by isozyme markers, were obtained for L. perenne x L. temulentum, L. temulentum x L. rigidum, L. temulentum x L. canariense and L. canariense x F. pratensis. This is the first report of this new form of Festulolium, which was obtained at a fairly high frequency, giving argument to a possible genetic proximity between L. canariense, an endemic species restricted to Atlantic islands, and F. pratensis, which has a more widespread, northern distribution. However, chromosome pairing analysis at meiosis did not support this conclusion, as the F1 L. canariense x F. pratensis definitely showed a higher level of asynapsis compared to that reported for L. perenne x F. pratensis. The apparently close relation between L. canariense and F. pratensis seen on the tree is therefore postulated to be an artefact, due to the low number of loci studied.     

普通小麦中两个ph系杂种对部分同源染色体配对的影响

为了揭示开县罗汉麦(KL)和中国春(CS)ph2a两个ph系的遗传差异,比较了32株KL/CSph2a//rye杂种的花粉母细胞减数分裂中期Ⅰ部分同源染色体配对。按交叉结数将F1植株分成4种配对类型:①与KL×rye处于同一水平4株;②与CSph2a×rye处于同一水平14株;③介于CSph2a×rye和KL×rye之间7株;④低配对7株。未发现配对比KL×rye高的植株。F1群体分离比表明:小麦KL不止一个控制部分同源染色体配对的基因位点,但都与ph2a基因位点不同。该研究结果对小麦远缘杂交与染色体工程研究具有一定参考价值。