Transfer of powdery mildew resistance from Aegilops variabilis into bread wheat

Winter hexaploid wheat (Triticum aestivum L.) was crossed with Aegilops variabilis to transfer resistance to powdery mildew into wheat. Following two backcrosses to wheat and from 5 to 9 generations of selfing, several disomic addition and substitution lines of hexaploid wheat resistant to the mildew pathogen were isolated. A pair of short satellited chromosomes was always observed in the resistant lines. Further evidence utilizing as markers for homoeologous group 1 HMW glutenin subunits and DNA hybridization with probe pGBX 3076 showed that an alien substitution involved this homoeologous group.     

Fertility restoration and nor suppression caused by Aegilops mutica chromosomes in alloplasmic hybrids and lines

By crossing Aegilops mutica with Triticum dicoccum as a bridge species and backcrossing with common wheat as a recurrent pollen parent, male sterile alloplasmic line(s) were produced. In progeny of the crosses, a self fertile plant with 42 chromosomes was selected and named R 20. From this plant several lines that possessed Rf (fertility restoring) genes and/or powdery mildew resistant genes were obtained. Apparently, the system of sterility-fertility of pollen can be applied for hybrid wheat production. In addition, the disease resistance may be used in breeding. The male fertile lines possessed one or more Ae. mutica sat-chromosome(s), which show the ability to suppress the nucleolar organizing regions of chromosomes 1B and 6B of common wheat. The relation between the sat-chromosomes and male fertility restoration is not yet clear. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetics of two mechanisms of resistance to Meloidogyne naasi (FRANKLIN) in an Aegilops variabilis Eig. accession

Summary Accession No. 1 of Aegilops variabilis has complete resistance to the root knot nematode, Meloidogyne naasi. F2 segregation in a cross between this and two susceptible accessions showed that one dominant gene named Rkn-mn1 prevented development of galls on the roots and consequently of female nematodes. The study of the numbers of females in galls on the F2 plants allowed detection of a recessive gene, Rkn-mnAv, suppressing development of J2 larvae into females. The presence of Rkn-mnAv also resulted in a decrease of the level of galling. Rkn-mn1 has already been introduced into wheat. The interest in transferring also Rkn-mnAv is discussed in relation to extending durability of the nematode resistance.     

An EMS-induced wheat mutant restoring fertility against photoperiod-sensitive cytoplasmic male sterility

Triticum aestivum cv. 'Norin 26' with Aegilops crassa cytoplasm shows photoperiod-sensitive cytoplasmic male sterility (PCMS). This alloplasmic line is almost completely male-sterile under long-day conditions (≥ 15h), but highly male-fertile under short-day conditions (≤ 14.5h). To obtain male—fertile mutants against PCMS, seeds of the alloplasmic line were treated with ethyl methane sulfonate (EMS). The M₃ generation was evaluated for PCMS expression, and one fertility-restoring (FR-mutant) line showing high male fertility under the long-day conditions was selected. Reciprocal F, hybrids between the FR-mutant and the alloplasmic 'Norin 26' showed male sterility under the long-day conditions, and continuous segregation with respect to the degree of fertility restoration occurred in their F₂ generations. These results indicate that multiple recessive mutations with minor effects, induced in the nuclear genome, are involved in the fertility restoration. In fact, no restriction-fragment-length polymorphisms of mitochondrial DNA between the FR-mutant and the alloplasmic 'Norin 26' are found.     

人工合成多倍体小麦及其供体种的高分子量 谷蛋白亚基组成研究

采用十二烷基磺酸钠—聚丙烯酰胺凝胶电泳（SDS-PAGE），分析了4份节节麦及其在此基础上形成的人工合成多倍体高分子量麦谷蛋白亚基（high-molecular-weight glutenin subunit，HMW-GS）的组成。研究结果表明，4份节节麦AS60-1、AS60-2、AS77和AS2383在Glu-D1位点上出现了4种不同的亚基类型，分别为2+10、5+12、5+10和2.1+10；2份节节麦人工加倍形成四倍体AS2390、AS2410的HMW-GS分别为2.1+10、5+10；3份节节麦—圆锥麦人工合成双二倍体RSP、SHW-L1及SHW-L2的HWM-GS分别为2*、17+18、5+10；2*、17+18、2+10和2+10。谷蛋白亚基呈现了共显性遗传，表明了节节麦高分子量谷蛋白基因能在人工多倍体情况下得到正常表达。此外，还对利用节节麦优良基因的方式作了讨论。     

Genetic polymorphisms at Gli-Dt gliadin loci in Aegilops tauschii as revealed by acid polyacrylamide gel and capillary electrophoresis

Gliadin variation at Gli‐D^t1 and Gli‐D^t2 loci in 198 Aegilops tauschii accessions was studied by acid polyacrylamide gel electrophoresis (A‐PAGE) and capillary electrophoresis (CE). High genetic polymorphisms were found at both gliadin coding loci, revealing a total of 184 and 169 gliadin variants at the Gli‐D^t1 and Gli‐D^t2 loci, respectively. In particular, 12 gliadin blocks encoded by different alleles were apparently expressed and readily identified in six synthetic hexaploids produced by hybridization between Triticum durum and Ae. tauschii accessions. Compared with Ae. tauschii ssp. eusquarrosa, the gliadin profile of the D genome in Ae. tauschii ssp. strangulata more resembles that of T. aestivum, supporting the view that the subspecies strangulata is the most likely progenitor of bread wheat. Capillary electrophoresis analysis showed that the method is capable of separating and characterizing gliadins with speed, in high resolution using small sample amounts, and is well‐suited to detect protein alleles and to identify desirable genotypes in wheat quality improvement.     

The Inheritance of Resistance to Septoria Glume Blotch III. The Wild Wheat Species Aegilops Jongissima

The genetics of resistance to Septoria glume blotch (caused by the pathogen Septoria nodorum Berk.) in the wild wheat species Ae. longissima was investigated. The resistance was characterized by two parameters measured on detached leaves — lesion size (LS) and length of latent period (LP), and by disease severity (DS) under field conditions. Generations F₁, F₂ and F₃, derived from a cross between two Ae. longissima accessions, were analyzed. The two parameters measured on detached leaves (LS and LP) were highly correlated, while DS was moderately correlated to both LS and LP. The mean LS and the mean LP of F₁ generation indicated considerable dominance for resistance in both parameters. The estimates of broad-sense and narrow-sense heritability were moderate for LS and LP (0.21—0.55). Narrow-sense heritability for DS was high (0.77). Estimates of the number of genes controlling each of the parameters (LS, LP, DS) were between 2.5—3.2. It is suggested that the resistance is controlled by three to four quantitative genes with a partial dominance of the alleles for resistance. Indications for genie interaction were found in LS and in LP. A model of inheritance containing complementation between dominant resistance-alleles is suggested. Highly resistant Ae. longissima accessions are recommended as sources of germplasm for improving the resistance of cultivated wheats to Septoria glume blotch. The possibility of using dominant alleles for resistance in hybrid cultivars is discussed.     

Use of the gene pools of Triticum turgidum ssp. dicoccoides and Aegilops squarrosa for the breeding of common wheat (T. aestivum), through chromosome-doubled hybrids

Summary Triticum turgidum ssp. dicoccoides (wild emmer wheat, AABB, 2n=28) and Aegilops squarrosa (goat grass, DD, 2n=14) comprise a rich reservoir of valuable genetic material, which could be useful for the breeding of common wheat (T. aestivum, AABBDD, 2n=42). Many accessions of both wild species, most of them selected for resistance to stripe rust, were used to make amphiploids. Two strategies were applied: (1) the production of autopolyploid cytotypes of the wild species, followed by hybridisation, and (2) the production of allotriploid interspecific hybrids, followed by doubling of the number of chromosomes. The first route was unsuccessful because of failure of the crosses between the autopolyploid cytotypes, possibly due to incongruity between the two species and to reduced fertility in the autopolyploid cytotypes. The second route yielded the desired synthetic hexaploids. However, the rate of success of the crosses was low and there were great differences between years, and within years between crosses. Embryo rescue was applied to obtain the primary hybrids (2n=21), which were highly sterile and had on average 0.3 bivalents and 20.4 univalents per pollen mother cell. Various abnormalities were recorded. Doubling of the number of chromosomes sometimes occurred spontaneously or was brought about by colchicine treatment. The large scale of the interspecific hybridisation programme ensured that one-third of the female and one-sixth of the male accessions were represented in the synthetic hexaploids.     

Chromosomal location of genes for resistance to powdery mildew in common wheat (Triticum aestivum L. em Thell.). 8. Gene Pm32 in a wheat-Aegilops speltoides translocation line

The wheat-Aegilops speltoides translocation line L501 exhibits a disease response pattern distinctive from that of documented powdery mildew genes after inoculation with differential Blumeria graminis tritici isolates. Results based on cytological C-bandings and monosomic analyses reveal that a dominant resistance gene derived from Ae. speltoides is located on a T1BL·1SS chromosome translocation in this line. The new gene is designated Pm32. This revised version was published online in July 2006 with corrections to the Cover Date.     

K型雄性不育小麦育性恢复基因的遗传特点及育性稳定性研究

利用2个K型小麦雄性不育系、21个恢复系及2个对照材料,组配杂交组合,经杂交、自交获得F1(AXR)和F2等世代材料,并考查其自交结实率,结合植物数量性状主基因+多基因混合遗传模型进行遗传分析,同时对部分组合的育性稳定性进行研究。结果表明:K型小麦雄性不育系的育性基因rf主要由雌配子传递,属配子体雄性不育类型;育性受2对加性-显性主基因+加性-显性多基因共同控制,且第1对主基因控制育性的作用强于第2对主基因;在F2群体中主基因的遗传率为62.44%,多基因遗传率为0,环境方差占表现型方差的37.56%,说明该类型小麦雄性不育性以主基因遗传为主,同时受多基因和环境的影响。育性稳定性研究表明,虽然K型细胞质雄性不育小麦的育性恢复年际间波动很大,但通过筛选可以获得恢复度高且稳定的恢复系,进而为杂交小麦的育种提供支持。