Biochemical, molecular, and cytogenetic technologies for characterizing 1RS in wheat: A review

Chromosome arm 1RS of rye ( Secale cereale L.), when transferred to wheat ( Triticum sp.), significantly influences variety performance, because it carries genes for resistance to disease and insect pathogens. Inserted into wheat, 1RS also promotes haploid production, affects end-product quality, and sometimes affects yield. Therefore, its detection by breeders and geneticists is important. The entire 1RS arm is present in chromosome substitutions and in Robertsonian translocations involving chromosomes 1A, 1B, or 1D of wheat. In recombinant lines, a segment of 1RS has been exchanged with a segment of a group-1 wheat chromosome. Determining the wheat chromosome arm involved in a translocation, the source of rye chromatin, and the amount of 1RS chromatin introduced is necessary for a complete characterization of the introgressed segment. Biochemical, molecular, and cytogenetic technologies are described which enable such a characterization of 1RS in wheat. Examples of using gel electrophoresis, high-performance liquid chromatography, monoclonal antibodies, rye-specific molecular probes, RFLP and PCR assays, chromosome banding, in situ hybridization, and flow cytometry are provided. A comparison of these technologies is made and the advantages and disadvantages of each technology are discussed relative to modern wheat breeding efforts. This revised version was published online in July 2006 with corrections to the Cover Date.     

Molecular cytogenetic identification of wheat-Elymus tsukushiense introgression lines

Elymus tsukushiense Honda (syn. Roegneria kamoji C. Koch) (2n = 6x = 42, S^tsS^tsH^tsH^tsY^tsY^ts) is a hexaploid species, distantly related to bread wheat Triticum aestivum L. em Thell (2n = 6x = 42, AABBDD). Apart from the delineation of evolutionary relationships, this species is a potential source of resistance to scab, a devastating disease of wheat caused by Fusarium graminearum Schw. A standard C-banded karyotype was established identifying all 21 chromosome pairs of E. tsukushiense. By using C-banding and genomic in situ hybridization analyses, three wheat-E. tsukushiense chromosome addition lines, one ditelosomic addition line, and one disomic substitution line were identified in BC₂ progenies from wheat × E. tsukushiense hybrids. Twenty DNA markers specific for the seven homoeologous groups of the Triticeae were used to determine the homoeology of the added E. tsukushiense chromosomes. The E. tsukushiense chromosomes in the addition lines NAU702, NAU703, and NAU701 were identified as belonging to homoeologous groups 1, 3, and 5, and thus, were designated as 1Ets#1, 3Ets#1, and 5Ets#1, respectively. NAU751 was identified as a disomic substitution line with chromosome 3A of wheat replaced by chromosome 3Ets#1. Line NAU702 has a high level of resistance to scab and will be used in chromosomal engineering and development of improved wheat germplasm for scab resistance breeding. This revised version was published online in July 2006 with corrections to the Cover Date.     

The effect of ovule age on ovary-slice culture and ovule culture in intraspecific and interspecific crosses with Tulipa gesneriana L.

The efficiency of two embryo rescue techniques, direct ovule culture and ovary-slice culture followed by ovule culture, is studied in crosses with Tulipa gesneriana as maternal genotype. The germination percentages increased, in most cases, significantly with increasing ages of te ovary-slices and ovules at the start of the cultures. The low number of embryos recovered at early culture dates is caused by a higher rate of embryo abortion and by retarded embryo development. The germination percentages for ovary-slice culture followed by ovule culture was mostly comparable to direct ovule culture. Unique hybrids have been obtained from the crosses T. gesneriana × T. agenensis and T. gesneriana × T. praestans. This revised version was published online in July 2006 with corrections to the Cover Date.     

Interspecific hybridization between Vigna unguiculata (L.) Walp. and V. vexillata (L.) A. Rich. through in vitro embryo culture

Immature embryos resulting from the cross V. vexillata × V. unguiculata were cultured on MS medium supplemented with 2,4-D (2 mg/l) and resulted in embryogenic calli. Thirteen hybrid regenerants were obtained via organogenesis by subculturing the calli on MS medium supplemented with BAP (2 mg/l) + adenine sulphate (40 mg/l) + CH (500 mg/l) + cowpea tender pod extract (10%). The interspecific regenerants showed intermediate morphological traits between the parents for leaf shape, pod colour and seed coat colour. The hybrid plants inherited stem, leaf and pod hairiness of the wild species which could serve as a mechanical barrier against viral vectors. Electrophoretic studies of two isozyme systems, peroxidase and esterase, also confirms the hybrid nature of the regenerants as they expressed unique bands of both parents. Cytological study of the meiotic chromosomes revealed high frequency of univalent formation in the hybrids suggesting that the genomes of the parental species are structurally differentiated. The hybrid regenerants exhibited high enzyme activity for three enzymes viz., peroxidase, polyphenol oxidase and phenyl alanine ammonia lyase over the cultivated parent which may be useful in conferring resistance against viral pathogens. This revised version was published online in July 2006 with corrections to the Cover Date.     

Characterization of Triticum aestivum/Psathyrostachys juncea derivatives by genomic in situ hybridization

Using the genomic in situ hybridization (GISH) technique, one translocation line, seven translocation-addition lines, five translocation plus translocation addition lines and two ditelosomic addition lines were identified in backcross progenies of Triticum aestivum L. -Psathyrostachys juncea (Fisch.) Nevski intergeneric hybrids. No complete P. juncea chromosomes were detected in the 25 lines studied. The results suggest that intact P. juncea chromosomes may be difficult to isolate in a wheat background. This revised version was published online in July 2006 with corrections to the Cover Date.     

Low level of polymorphism detected by SSR probes in bread wheat

In-gel hybridization patterns were studied in a set of nine diverse bread wheat ( Triticum aestivum L. em. Thell) genotypes using 23 simple sequence repeat (SSR) probes in combination with 14 different restriction enzymes. Multilocus fingerprints due to SSR probes, shown earlier to be characteristic of a majority of plant genomes, were not obtained and only a very low level of polymorphism was detected when using as many as 142 probe-enzyme combinations. The hybridization of a prominent solitary high molecular weight fragment (> 23 kb) with a number of SSR probes suggested the presence of these SSRs (microsatellites) within the long stretches of repeated DNA sequences. This indicates that the genome of bread wheat differs from that of other plants in the organization and distribution of SSRs and that SSR probes detect very little polymorphism.     

Characterization of wheat-triticale doubled haploid lines by cytological and biochemical markers

Five wheat-triticale doubled haploid (DH) lines— M08, V209, DH220-14-2, DH696-3-4 and M16 —derived from anther culture of F₁s resulting from crosses involving hexaploid or octoploid triticale × hexaploid wheat, were characterized by cytological and biochemical markers. Cytological evidence from genomic in situ hybridization and C-banding indicated that DH lines M08 and V209 (2n= 42) each contained a pair of 1BL/1RS translocation chromosomes. DH220-14-2 (2n= 42) was also a translocated line with two pairs of chromosomes containing small fragments of rye. One of the translocation fragments carried the Sec-1R gene originating from the satellite region of 1RS; the origin of the other one remains unknown. DH696-3-4 (2n= 42) contained a 3D(3R) substitution. In M16 (2n= 44), three pairs of rye chromosomes, 3R, 4R and 6R, were present, 4R as an addition and 3D(3R) and 6D(6R) as substitutions. Biochemical, isozyme and storage protein markers confirmed the cytological conclusions. The advantages of transferring alien chromosomes or chromosome fragments into wheat and creating alien aneuploid lines by anther culture of hybrid F¹s are discussed.     

多花黑麦草和四倍体苇状羊茅属间杂种F#-1及其双倍体的细胞遗传学研究

本研究获得了多花黑麦草（Lolium multiflorum Lam 2n=2x=14）和四倍体苇状羊茅（Festuca arundinacea var.glaucescens Boiss 2n=4x=28）的属间杂种。Lmx Fa.g杂种在形态上呈中间型,而反交杂种则倾向于母本。杂种的细胞学研究表明：多花黑麦草的染色体组（A）与四倍体苇状羊茅的两组染色体（B和B′）亲和性差;相对来说,羊茅属的细胞质有利于A、B、B′三组染色体的配对。杂种F#-1花药不开裂,花粉畸形败育。合成的双倍体细胞学上不稳定,花粉KI-I#-2可染率极低。本文还讨论了利用杂种的途径和实践意义。     

甜菜数量性状杂交综合指数的研究

通过对40份参试材料7个主要性状的杂交综合指数的统计分析,阐述了杂交综合指数的大小与后代杂种优势、亲本特殊配合力之间的关系,表明它们之间具有较强的一致性[r#-（u·Mp）=0.7226,r#-（u·Sij）=0.3492],并明显地好于遗传距离与杂种优势、亲本特殊配合力之间的相关性[r#-（D#+2·Mp）=0.6135,r#-（D#+2·Sij）=0.2121];同时对780个杂交综合指数进行聚类分析,共划分5个类群,类群间平均杂交综合指数u=18.209,应在（u*+-）≥18.209的类群之间选择杂交亲本。本试验中满足上述条件的有Ⅰ和Ⅴ、Ⅲ和Ⅳ、Ⅳ和Ⅴ。     

Aspects of fusion combining ability of dihaploidSolanum tuberosum L.: influence of the cytoplasm

Summary Creation from 4x hybrid clones from protoplast fusion of 2x clones of potato was evaluated. Besides combined nuclear genomes, composition of the cytoplasm significantly influenced the phenotypic traits of hybrid clones. To ascertain the influence of parental cytoplasm on the success of protoplast fusion and regeneration of hybrid plants, data from 74 fusion combinations of 50 dihaploid clones were analyzed. The majority of dihaploid breeding clones belonged to the cytoplasm types Wα, Tβ and Wγ. When the closely related mt types α, β and γ were used, fusion combinations had a better combining ability compared with more distantly related cytoplasms δ and ⃛. Fusions containing the same mitochondrial type (homofusions) were not superior to closely related mitochondrial types. However, homofusions of cytoplasm type Wα yielded significantly more hybrids than homofusions of type Tβ. In general, parental cytoplasm types had little impact on the fusion combining behaviour. Thus the cytoplasm type of the fusion parents is not a suitable marker for predicting the combining ability in protoplast fusion experiments.