Physical mapping of a 7A.7D translocation in the wheat-Thinopyrum ponticum partial amphiploid BE-1 using multicolour genomic in situ hybridization and microsatellite marker analysis

Production and First Assessment of Iranian Secondary Tritipyrum Genotypes by GISH and AFLP Markers

Background

Non-Iranian Primary Tritipyrum (2n=6x=42, AABBE^bE^b) set seed after Triticale (2n=6x=42, AABBRR) and Tritordeum (2n=6x=42, AABBH^cH^c) but, due to a few undesirable agronomic traits, it cannot fulfil the commercial expectations of farming.

Objectives

To remove these deficiencies, six hexaploid Tritipyrum lines were crossed with four Iranian bread wheat cultivars which led to the production of 107 (F₁), 479 (F₂), 768 (F₃), and 1539 (F₄) Iranian Secondary Tritipyrum Genotypes (ISTG) seeds. This study was carried out for selecting the plants potentially carry the 5E^b chromosome/s and are good candidates for salt tolerant by GISH and RFLP markers.

Materials and Methods

The procedure involved extracting the total DNA content of 209 plants, including non-Iranian primary Tritipyrum lines, Iranian wheat cultivars, Chinese Spring addition, and substitution lines for 5E^b and Iranian secondary Tritipyrum genotypes (ISTG: F₁, F₂, F₃, F₄). Genomic in situ Hybridization (GISH) on mitotic spreads of fertile new Iranian secondary Tritipyrum genotypes (ISTG) was carried out to demonstrate the feasibility of single E^b chromosomes. There were three trials of 18 Fragment Length Polymorphism (AFLP) EcoRI/MseI primers to identify the presence of the 5E^b chromosome in 105 ISTG plants, along with four wheat addition lines and substitution lines for the 5E^b chromosome.

Results

GISH on mitotic spreads demonstrated the feasibility of producing 75 plants out of 105 fertile new Iranian secondary Tritipyrum genotypes (ISTG) with 0-14 single E^b chromosomes. Among the mentioned markers, only the E₃₆/M₅₉ marker showed 43, 50, 30 and 47 identical bands, respectively, in contrast to 53 expected bands in all plants with the 5E^b chromosome which indicated 21, 33, 9 and 6 out of 75 ISTG plants, respectively, with the 5E^b chromosome.

Conclusion

This study indicated that 69 ISTG Tritipyrum plants were potentially carry the 5E^b chromosome/s and are good candidates for salt tolerant tests in comparison with Iranian modern bread wheat cultivars.

Physical mapping of DNA markers linked to stem rust resistance gene Sr47 in durum wheat

Markers linked to stem rust resistance gene Sr47 were physically mapped in three small Aegilops speltoides chromosomal bins. Five markers, including two PCR-based SNP markers, were validated for marker-assisted selection. In durum wheat (Triticum turgidum subsp. durum), the gene Sr47 derived from Aegilops speltoides conditions resistance to race TTKSK (Ug99) of the stem rust pathogen (Puccinia graminis f. sp. tritici). Sr47 is carried on small interstitial translocation chromosomes (Ti2BL-2SL-2BL·2BS) in which the Ae. speltoides chromosome 2S segments are divided into four bins in genetic stocks RWG35, RWG36, and RWG37. Our objective was to physically map molecular markers to bins and to determine if any of the molecular markers would be useful in marker-assisted selection (MAS). Durum cultivar Joppa was used as the recurrent parent to produce three BC₂F₂ populations. Each BC₂F₂ plant was genotyped with markers to detect the segment carrying Sr47, and stem rust testing of BC₂F₃ progeny with race TTKSK confirmed the genotyping. Forty-nine markers from published sources, four new SSR markers, and five new STARP (semi-thermal asymmetric reverse PCR) markers, were evaluated in BC₂F₂ populations for assignment of markers to bins. Sr47 was mapped to bin 3 along with 13 markers. No markers were assigned to bin 1; however, 7 and 13 markers were assigned to bins 2 and 4, respectively. Markers Xrwgs38a, Xmag1729, Xwmc41, Xtnac3119, Xrwgsnp1, and Xrwgsnp4 were found to be useful for MAS of Sr47. However, STARP markers Xrwgsnp1 and Xrwgsnp4 can be used in gel-free systems, and are the preferred markers for high-throughput MAS. The physical mapping data from this study will also be useful for pyramiding Sr47 with other Sr genes on chromosome 2B.

Corantes comumente empregados na citogenética vegetal

O emprego dos corantes, na citogenética vegetal, data de muitos anos, uma vez que as pesquisas nas áreas da citologia e histologia vêm sendo desenvolvidas constantemente desde os primeiros estudos celulares no século XIX. Inicialmente, eram extraídos de fontes vegetais ou animais, sendo atualmente produzidos sinteticamente em escala comercial. Os corantes são classificados em não fluorescentes e fluorescentes, conforme suas propriedades químicas e a escolha de uso é de acordo com o tipo de estrutura celular ou grupo celular a ser analisado. A diversidade de tipos e compostos químicos existentes nos diferentes corantes proporciona sua aplicação em estudos avançados na citogenética clássica e molecular. Uma revisão de suas propriedades químicas e emprego é apresentada para os corantes não fluorescentes orceína, hematoxilina, Giemsa, carmin; e para os fluorescentes 4',6-diamidino-2-fenilindol (DAPI), cromomicina A (CMA), fluoresceína e rodamina.

Characterization of a new 4BS.7HL wheat–barley translocation line using GISH, FISH, and SSR markers and its effect on the β-glucan content of wheat

A spontaneous interspecific Robertsonian translocation was revealed by genomic in situ hybridization (GISH) in the progenies of a monosomic 7H addition line originating from a new wheat ‘Asakaze komugi’ × barley ‘Manas’ hybrid. Fluorescence in situ hybridization (FISH) with repetitive DNA sequences (Afa family, pSc119.2, and pTa71) allowed identification of all wheat chromosomes, including wheat chromosome arm 4BS involved in the translocation. FISH using barley telomere- and centromere-specific repetitive DNA probes (HvT01 and (AGGGAG)n) confirmed that one of the arms of barley chromosome 7H was involved in the translocation. Simple sequence repeat (SSR) markers specific to the long (L) and short (S) arms of barley chromosome 7H identified the translocated chromosome segment as 7HL. Further analysis of the translocation chromosome clarified the physical position of genetically mapped SSRs within 7H, with a special focus on its centromeric region. The presence of the HvCslF6 gene, responsible for (1,3;1,4)-β-d-glucan production, was revealed in the centromeric region of 7HL. An increased (1,3;1,4)-β-d-glucan level was also detected in the translocation line, demonstrating that the HvCslF6 gene is of potential relevance for the manipulation of wheat (1,3;1,4)-β-d-glucan levels.