Development of T. aestivum L.eH. californicum Alien Chromosome Lines and Assignment of Homoeologous Groups of Hordeum californicum Chromosomes

Hordeum californicum （2n = 2x = 14, HH） is resistant to several wheat diseases and tolerant to lower nitrogen. In this study, a molecular karyotype of H. californicum chromosomes in the Triticum aestivum L. cv. Chinese Spring （CS）-H. californicum amphidiploid （2n = 6x = 56, AABBDDHH） was established. By genomic in situ hybridization （GISH） and multicolor fluorescent in situ hybridization （FISH） using repetitive DNA clones （pTa71, pTa794 and pSc119.2） as probes, the H. californicum chromosomes could be differentiated from each other and from the wheat chromosomes unequivocally. Based on molecular karyotype and marker analyses, 12 wheat--alien chromosome lines, including four disomic addition lines （DAH1, DAH3, DAH5 and DAH6）, five telosomic addition lines （MtH7L, MtHIS, MtH1L, DtH6S and DtH6L）, one multiple addition line involving H. californicum chromosome H2, one disomic substitution line （DSH4） and one translocation line （TH7S/1BL）, were identified from the progenies derived from the crosses of CS-H. californicum amphidiploid with common wheat varieties. A total of 482 EST （expressed sequence tag） or SSR （simple sequence repeat） markers specific for individual H. californicum chromosomes were identified, and 47, 50, 45, 49, 21, 51 and 40 markers were assigned to chromosomes H1, H2, H3, H4, H5, H6 and H7, respectively. According to the chromosome allocation of these markers, chromosomes H2, H3, H4, H5, and H7 of H. californicum have relationship with wheat homoeologous groups 5, 2, 6, 3, and 1, and hence could be designated as 5Hc, 2He, 6Hc, 3Hc and 1Hc, respectively. The chromosomes H1 and H6 were designated as 7Hc and 4Hc, respectively, by referring to SSR markers located on rye chromosomes.

Development of EST-PCR markers specific to the long arm of chromosome 6V of Dasypyrum villosum

Expressed sequence tags-derived polymerase chain reaction(EST-PCR) molecular markers specific for alien chromosomes can be used to not only monitor the introgressed alien chromatin in wheat background, but also provide the evidence of the syntenic relationship between homoeologous chromosomes. In the present study, in order to develop high density and evenly distributed molecular markers specific for chromosome 6 VL of Dasypyrum villosum, 297 primer pairs were designed based on the expressed sequence tags(EST) sequences, which were previously mapped in different bins of the long arms of wheat homoeologous 6 AL, 6 BL, and 6 DL. By using the Triticum aestivum, D. villosum, T. durum-D. villosum amphiploid, and T. aestivum-D. villosum alien chromosome lines involving chromosome 6 V, it was found that 32(10.77%) primers could amplify specific bands for chromosome 6 V, and 31 could be allocated to chromosome arm 6 VL. These 6 VL specific markers provided efficient tools for the characterization of structural variation involving the chromosome 6 VL in common wheat background as well as for the selection of useful genes located on 6 VL in breeding programs.

Identification and transferring of a new Fusarium head blight resistance gene FhbRc2 from Roegneria ciliaris 3ScL chromosome arm into common wheat

Fusarium head blight(FHB)threatens wheat production worldwide.Utilization of FHB resistant varieties is the most effective solution for disease control.Owing to the limited sources of FHB resistance,mining of novel resistance genes is crucial.Here,we report an FHB resistance gene from a wild wheat relative species,Roegneria ciliaris and developed FHB resistant germplasm containing this gene.Wheat-R.ciliaris disomic addition line DA3S^(c) showed enhanced type II FHB resistance compared to its sister line 3S^(c)-Null without chromosome 3S^(c),indicating that the resistance was contributed by the addition of 3S^(c).The resistance gene on 3S^(c) was validated using F_(2) and F_(2:3) populations derived from the cross between DA3S^(c) and susceptible Aikang 58(a susceptible cultivar),demonstrating that the lines with 3S^(c) had significantly enhanced FHB resistance compared to the individuals without 3S^(c).This was the second resistance gene identified in R.ciliaris,designated FhbRc2.To transfer FhbRc2 to common wheat,we produced a doublemonosomic chromosome population by crossing DA3S^(c) with the Chinese Spring nulli-tetrasomic line N3DT3B.Eight alien chromosome lines containing 3S^(c) were identified using genomic/fluorescence in situ hybridization and 3S^(c)-specific marker analysis.Only the lines carrying the long arm of 3S^(c) conferred FHB resistance,further locating FhbRc2 on 3S^(c)L.A compensating wheat-R.ciliaris Robertsonian translocation line T3DS·3S^(c)L harboring FhbRc2 is developed and provides a potential genetic resource in wheat breeding for enhanced FHB resistance.