Nucleolus organizer competition in Triticum aestivum — Aegilops umbellulata chromosome addition lines

Summary The nucleolar organizer activity of wheat (Triticum aestivum, AABBDD) and Aegilops umbellulata (UU) chromosomes have been analyzed in the complete set of the chromosome addition lines by using a highly reproducible silver-staining procedure. Chromosomes 1U and 5U produce the partial inactivation of wheat nucleolar organizer chromosomes 6B, 1B and 5D. The chromosomes D and G from Ae. umbellulata, which are not SAT-chromosomes, seem to specifically influence the activity of wheat NORs. The predominant status of the U genome with respect to nucleolar competition in the Triticeae is confirmed.     

Cytogenetic relationship ofAegilops longissima chromosomes with common wheat chromosomes

The relationships of three wheat-Aegilops longissima chromosome addition lines A, C, and D with homoeologous wheat chromosomes were studied in PMC meiosis. Substitutions of alien chromosome A for wheat chromosome 6 B, chromosome C for 1 B and chromosome D for 4 B were obtained. The production of 4 BS/C and 7 BS/D chromosome translocations indicated cytogenetic relationships of C partially to homoeologous wheat chromosomes of group 1 and 4, and D partially to homoeologous wheat chromosomes of group 4 and 7.     

Eyespot resistance gene Pch-1 in H-93 wheat lines. Evidence of linkage to markers of chromosome group 7 and resolution from the endopeptidase locus Ep-D1b

Summary Gene Pch1, which confers resistance to eyespot disease (Pseudocercosporella herpotrichoides Fron), has been located on chromosome 7D in the H-93 wheat-Aegilops ventricosa transfer lines using isozyme markers and DNA probes corresponding to group 7 chromosomes. Previous experiments had failed to ascertain this location. The lack of segregation of the resistance trait in progeny from reciprocal crosses between lines H-93-70 and VPM1 indicates that their respective resistance factors are allelic. Line H-93-51 carries the endopeptidase allele Ep-D1b but is susceptible to eyespot, which indicates that resistance to eyespot is not a product of the Ep-D locus, as had been proposed in a previous hypohesis.     

Inter- and intraplant C-banding polymorphism in one population ofAegilops comosa subsp.comosa var.comosa (Poaceae)

The Giemsa C-banding pattern of the chromosomes of the native self-pollinatedAegilops comosa subsp.comosa var.comosa was studied. Six of the seven chromosomes of the haploid genome were found to be polymorphic for C-banding patterns. Chromosome A had four variants, chromosome E three variants and each of the chromosomes B, D, and F two variants. Chromosomes E and G were polymorphic for arm length and arm ratio.This paper is part of the doctoral dissertation ofA. Georgiou.     

Analysis of the resistance of Aegilops squarrosa to the wheatgrass mildew fungus by using the gene-for-gene reationship

Summary Pm10 and Pm15, resistance genes to Erysiphe graminis f. sp. agropyri, are located on the D genome of common wheat. It was determined whether or not they were carried by existing lines of the D genome donor, Aegilops squarrosa, using the gene-for-gene relationship. Two lines of Ae. squarrosa tested (one was var. meyeri and the other was var. anathera) were susceptible to culture Tk-1 of E. graminis f. sp. tritici and were highly resistant to culture Ak-1 of E. graminis f. sp. agropyri. The two lines were inoculated with an F₁ population derived from the cross Ak-1 × Tk-1. Comparative analyses of the segregation patterns revealed that Ppm10 and Ppm15, avirulence genes corresponding to Pm10 and Pm15, respectively, are involved in the avirulence of Ak-1 on var. meyeri and var. anathera, respectively. According to the gene-for-gene relationship, var. meyeri and var. anathera were inferred to carry Pm10 and Pm15, respectively. Analysis with a synthetic hexaploid confirmed the inference.     

根据叶表皮微形态特征探讨山羊草属基因在小麦属中的渗入：Ⅰ.组间途径

解剖观察了小麦属３个组、山羊草属６个组的叶片远轴面表皮,并根据表皮上长细胞、短细胞、气孔器细胞、刺毛和大毛在各个类群中形态、数量和分布式样的差异,从组群角度对山羊草属基因在小麦属中的渗入进行了分析。结果表明：小麦属中除线穗组无山羊草属基因侵入外,其余扁穗组和柱穗组皆为山羊草属基因可能的受体类群;山羊草属中除无芒山羊草组、顶芒山羊草组和小伞山羊草组无基因输出外,拟斯卑尔脱组和节节麦组均有基因进入小麦     

Origin and differentiation of Aegilops triuncialis L. as determined by esterase isozyme analysis

Summary Banding patterns of esterase isozymes in Aegilops triuncialis (2n = 28, genome formula C^uC^uCC) and its putative parental species, Ae. umbellulata (2n = 14, C^uC^u) and Ae. caudata (2n = 14, CC), were studied by the gel isoelectric focusing method using pH 6–8 carrier ampholite. Zymogram phenotypes of both parents were quite uniform. Seven zymogram phenotypes (designated as phenotypes 1 to 7) were found among the 260 strains of Ae. triuncialis examined. Of these phenotypes, phenotype 1 was identical to the zymogram phenotype produced by the ancestral species, Ae. umbellulata, and bands considered to have been derived from Ae. caudata were absent in this phenotype. Phenotype 3 had all bands of both parents. The other phenotypes differed greatly from phenotype 3. Therefore, phenotype 3 was considered to be most primitive of the 7 types, and the Ae. triuncialis strains which showed phenotype 3 to be the most primitive of the strains examined. If Ae. triuncialis originated as a hybrid between Ae. umbellulata and Ae. caudata, the zymogram phenotype must have been phenotype 3, in which the isozymes of both parental species are present. Whether the phenotypes other than type 3 were due to introgressive hybridization could not be verified, but they were considered in this article to be a consequence of a rearrangement of chromosomes.Contribution from the Laboratory of Genetics, Faculty of Agriculture, Kyoto University No. 432     

The application of wheat microsatellites to identify disomic Triticum aestivum-Aegilops markgrafii addition lines

 We describe the use of wheat microsatellites for the discrimination of Aegilops markgrafii chromosomes. Twenty out of eighty eight wheat microsatellites (WMS) tested were able to distinguish Triticum aestivum-Ae. markgrafii addition lines. Six, three, three, one and six of 18 WMS can be used as markers for single Ae. markgrafii chromosomes B, C, D, F and G, respectively. Addition line A is not available but additional bands, appearing only in Ae. markgrafii and the T. aestivum-Ae. markgrafii amphiploid and not in any of the available addition lines, indicate that three WMS detect markers for Ae. markgrafii chromosomes A. Addition line E could not be detected by any of the WMS markers applied, although the 20 WMS represented all the homologous groups of wheat. All three WMS located on the short arm of group-2 chromosomes were located on Ae. markgrafii chromosome B; three of four WMS, located on the long arm of wheat group-2 chromosomes, were specific to Ae. markgrafii chromosome G and three of four WMS, specific to group-5 chromosomes, were markers for Ae. markgrafii chromosome C, indicating the homoeology of these wheat chromosome arms with the respective Ae. markgrafii chromosomes. Received: 29 May 1997 / Accepted: 10 September 1997     

利用粘果山羊草细胞质1B/1R易位系诱导小麦单倍体频率的研究

用具有粘果山羊草(Ae. kotschyi)细胞质的1B/1R易位系转育成的K型小麦雄性不育系为基本材料,通过随体数目和C—显带技术鉴定了不育系、恢复系及其亲本的染色体组成,以中国春重双端体2t″1B和缺—四体1B°1D~Ⅳ与其杂交,观察了F_1减数分裂中期Ⅰ的染色体构型和C—显带特征。调查了有代表性的10个k型不育系及其中三个不育系与中国春重双端体2t″1B或缺—四体1B°1D~Ⅳ杂交F_1的单倍体诱导频率。结果表明,多数k型1B/1R不育系均可产生较高频率的单倍体,但不育系间差异很大,个别k型1B/1R不育系不产生单倍体,说明单倍体的产生除受1R短臂上的诱导单倍体基因作用外,还受其他基因的影响,同时也受父本基因型和染色体结构的影响,试验证明,1B染色体缺失或端体等非整倍体作为父本可以大大提高诱导单倍体的频率(接近70%),这种方法诱导产生的是单倍体种子,一般发芽正常,发育良好,在异质小麦育种方面具有重要实践意义。但由于这种单倍体均为孤雌生殖所致,应用受到一定限制,因此本文提出了如何应用的参考方案。     

Synthetic hexaploid wheat enhances variation and adaptive evolution of bread wheat in breeding processes

Synthetic hexaploid wheat (SHW) that combines novel and elite genes from the tetraploid wheat Triticum turgidum L. and wild ancestor Aegilops tauschii Coss., has been used to genetically improve hexaploid common wheat. The abundant genetic diversity in SHW can effectively make breakthroughs in wheat genetic improvement through the inclusion of increased variation. In this paper, we reviewed the current advances in research and utilization of the primary SHW lines and SHW-derived wheat varieties that have enhanced evolution of modern wheat under conditions of natural and artificial selection in southwestern China. Using primary SHW lines, four high-yielding wheat varieties have been developed. In addition, using the SHW-derived varieties as breeding parents, 12 new wheat varieties were also developed. Results of genotype–phenotype and fingerprint analysis showed that the introgressed alleles from SHW lines have contributed a great number of elite characters to the new wheat varieties, and these elite characters include disease resistance, more spikes per plant, more grains per spike, larger grains, and higher grain-yield potential. We found that the primary SHW lines and SHW-derived varieties have identifiable effects to enhance genetic variation and adaptive evolution of modern hexaploid wheat, which significantly increased the grain yields of hexaploid wheat in recent years. These findings have significant implications in the breeding of high-yielding wheat varieties resistant to biotic and abiotic stresses using SHW as genetic resources.