Elimination of the yellow pigment gene PSY-E2 tightly linked to the Fusarium head blight resistance gene Fhb7 from Thinopyrum ponticum

Fhb7 is a major gene that was transferred from Thinopyrum ponticum to chromosome 7D of wheat(Triticum aestivum)and confers resistance to both Fusarium head blight(FHB)and Fusarium crown rot(FCR).However,Fhb7 is tightly linked to the PSY-E2 gene,which causes yellow flour,limiting its application in breeding.To break this linkage,marker K-PSY was developed for tagging PSY-E2 and used with Fhb7 markers to identify recombination between the two genes.Screening 21,000 BC1F2 backcross progeny(Chinese Spring ph1bph1b*2/SDAU 2028)revealed two Fhb7^(+)wheat-Tp7el_(2)L lines,Shannong 2–16and Shannong 16–1,that carry a desired truncated Fhb7^(+)translocation segment without PSY-E2.The two lines show levels of resistance to FHB and FCR similar to those of the original translocation line SDAU 2028,but have white flour.To facilitate Fhb7 use in wheat breeding,STS markers were developed and used to isolate Fhb7 on a truncated Tp7el_(2) translocation segment.Near-isogenic lines carrying the Fhb7^(+)segment were generated in the backgrounds of three commercial cultivars,and Fhb7^(+)lines showed increased FHB and FCR resistance without yield penalty.The breakage of the tight linkage between Fhb7 and PSY-E2 via homoeologous recombination provides genetic resources for improvement of wheat resistance to FHB and FCR and permit the large-scale deployment of Fhb7 in breeding using marker-assisted selection.

Molecular cytogenetic characterization of a novel wheat-Thinopyrum intermedium introgression line tolerant to phosphorus deficiency

Thinopyrum intermedium has been used as a resource for improving resistance to biotic and abiotic stresses and yield potential in common wheat. Wheat line SN304 was derived from a cross between common wheat cultivar Yannong 15 and Th. intermedium. Genomic in situ hybridization(GISH) produced no hybridization signal in SN304 using Th. intermedium genomic DNA as a probe, but fluorescence in situ hybridization(FISH) using oligonucleotides AFA-3, AFA-4, pAs1-1, pAs1-3, pAs1-4, pAs1-6, pSc119.2-1,and(GAA)10 as probes detected hybridization signals on chromosomes 2 A, 7 A, 2 B, 3 B, 6 B, and 7 B in SN304 that differed from Yannong 15. Results of specific markers also indicated that there were Th. intermedium chromatin introgressions on different chromosomes in SN304. In a hydroponic culture experiment, SN304 not only produced more biomass and higher stem and leaf dry weight but also accumulated more phosphorus than Yannong 15 under phosphorus-deficiency stress. Moreover, SN304 produced a lower pH and released more organic acids, especially oxalic acid, than Yannong 15, which suggests that SN304 exudates enabled more absorbance of P than Yannong 15 under comparable conditions.The results indicate that SN304 is a wheat-Th. intermedium introgression line with tolerance to phosphorus-deficiency stress.

Characterization of a Triticum aestivum-Aegilops germplasm line presenting reduced plant height and early maturation

Plant height plays an important role in the potential and stability of crop yields and represents one of the most important agronomic traits of wheat. Although more than 30 dwarfing genes have been identified in wheat, only a few are used in wheat breeding, which has narrowed the genetic basis of newly developed varieties. Therefore, continually identifying new dwarfing genes is required to produce improved wheat cultivars. TA001 is a new germplasm line marked by reduced plant height and early maturation, and it was derived from a hybridization between the common wheat Yannong 15 and the Aegilops ventricosa × Aegilops cylindrica amphiploid SDAU18. In this study, cytological observations, agronomic trait examinations, genomic in situ hybridization(GISH), multicolor genomic in situ hybridization(mc-GISH), multicolor fluorescence in situ hybridization(mc-FISH), SSR analysis and seed storage protein electrophoresis were combined to determine the cytological stability, main agronomic traits, chromosomal constituents and seed storage protein subunits of TA001. Twenty-one bivalents were observed in most of the pollen mother cells at metaphase I(PMCs MI) in TA001, which housed 42 chromosomes, and the chromosomes in most pollen mother cells at anaphase I(PMCs AI)displayed 21/21 segregation. Twenty bivalents plus two univalents were simultaneously observed in most of the PMCs MI of the hybrid F_1 between TA001 and Yannong 15. TA001 possessed all chromosomes from genomes A, B and D except for chromosome 7B, which was replaced by one pair of N-genome chromosomes from Aegilops ventricosa. Several pairs of chromosomes in TA001 exhibited different FISH patterns from the equivalent chromosomes in Yannong 15. TA001 housed alien genetic materials from Aegilops ventricosa and Aegilops cylindrica and possessed new glutenin and gliadin subunits specific to SDAU18, as revealed by molecular marker analysis and protein electrophoresis respectively.

Molecular mapping of a novel wheat powdery mildew resistance gene Ml92145E8-9 and its application in wheat breeding by marker-assisted selection

Powdery mildew, caused by Blumeria graminis f. sp. tritici(Bgt), is one of the most devastating diseases of common wheat(Triticum aestivum L.). The wheat line 92145 E8-9 is immune to Bgt isolate E09. Genetic analysis reveals that the powdery mildew resistance in 92145 E8-9 is controlled by a single dominant gene, temporarily designated Ml92145 E8-9. Bulkedsegregant analysis(BSA) with simple sequence repeat(SSR) markers indicates that Ml92145 E8-9 is located on chromosome 2 AL. According to the reactions of 92145 E8-9,VPM1(Pm4 b carrier), and Lankao 906(PmLK906 carrier) to 14 Bgt isolates, the resistance spectrum of 92145 E8-9 differs from those of Pm4 b and PmLK906, both of which were previously localized to 2 AL. To test the allelism among Ml92145 E8-9, Pm4 b and PmLK906, two F2 populations of 92145 E8-9 × VPM1(Pm4 b) and 92145 E8-9 × Lankao 906(PmLK906) were developed in this study. Screening of 784 F2 progeny of 92145 E8-9 × VPM1 and 973 F2 progeny of 92145 E8-9 × Lankao 906 for Bgt isolate E09 identified 37 and 19 susceptible plants, respectively. These findings indicated that Ml92145 E8-9 is non-allelic to either Pm4 b or PmLK906. Thus, Ml92145 E8-9 is likely to be a new powdery mildew resistance gene on2 AL. New polymorphic markers were developed based on the collinearity of genomic regions of Ml92145 E8-9 with the reference sequences of the International Wheat Genome Sequencing Consortium(IWGSC). Ml92145 E8-9 was mapped to a 3.6 c M interval flanked by molecular markers Xsdauk13 and Xsdauk682. This study also developed five powdery mildew-resistant wheat lines(SDAU3561, SDAU3562, SDAU4173, SDAU4174, and SDAU4175)using flanking marker-aided selection. The markers closely linked to Ml92145 E8-9 would be useful in marker-assisted selection for wheat powdery mildew resistance breeding.

禾本科作物芒遗传研究进展

芒是许多禾本科作物穗部的重要结构,不仅可以作为区分不同品种以及基因定位的重要形态标记,而且在禾谷类作物的种子传播、籽粒灌浆、蒸腾作用及产量形成等方面起重要作用。该文综述了小麦(Triticum aestivum)、大麦(Hordeum vulgare)和水稻(Oryza sativa)芒的结构、功能与遗传调控机制研究进展,以期为芒性状遗传机理的进一步研究及其在育种中的应用提供参考。

Chromosomal Constitutions and Reactions to Powdery Mildew and Stripe Rust of Four Novel Wheat-Thinopyrum intermedium Partial Amphiploids

As a staple food crop for one-third of the world＇s population, common wheat （Triticum aestivum L., 2n = 6x = 42, AABBDD） plays an important role in humans＇ food security. However, the genetic variation of cultivated wheat has been dramatically narrowed by genetic erosion under the modem cultivation system, resulting in vulnerability to biotic and abiotic stresses （Jiang et al., 1994; Friebe et al., 1996）. The wild relatives of wheat represent a large reservoir of superior genes, and transferring these alien genes to modem cultivars through chromosome engineering is a successful method of broadening the genetic diversity of wheat （Chen et al., 2003;