Identification of a Wheat-Psathyrostachys huashanica 7Ns Ditelosomic Addition Line Conferring Early Maturation by Cytological Analysis and Newly Developed Molecular and FISH Markers

Early maturation is an important objective in wheat breeding programs that could facilitate multiple-cropping systems, decrease disaster- and disease-related losses, ensure stable wheat production, and increase economic benefits. Exploitation of novel germplasm from wild relatives of wheat is an effective means of breeding for early maturity. Psathyrostachys huashanica Keng f. ex P. C. KUO (2n=2x=14, NsNs) is a promising source of useful genes for wheat genetic improvement. In this study, we characterized a novel wheat-P. huashanica line, DT23, derived from distant hybridization between common wheat and P. huashanica. Fluorescence in situ hybridization (FISH) and sequential genomic in situ hybridization (GISH) analyses indicated that DT23 is a stable wheat-P. huashanica ditelosomic addition line. FISH painting and PCR-based landmark unique gene markers analyses further revealed that DT23 is a wheat-P. huashanica 7Ns ditelosomic addition line. Observation of spike differentiation and the growth period revealed that DT23 exhibited earlier maturation than the wheat parents. This is the first report of new earliness per se (Eps) gene(s) probably associated with a group 7 chromosome of P. huashanica. Based on specific locus-amplified fragment sequencing technology, 45 new specific molecular markers and 19 specific FISH probes were developed for the P. huashanica 7Ns chromosome. Marker validation analyses revealed that two specific markers distinguished the Ns genome chromosomes of P. huashanica and the chromosomes of other wheat-related species. These newly developed FISH probes specifically detected Ns genome chromosomes of P. huashanica in the wheat background. The DT23 line will be useful for breeding early maturing wheat. The specific markers and FISH probes developed in this study can be used to detect and trace P. huashanica chromosomes and chromosomal segments carrying elite genes in diverse materials.

Development and Molecular Cytogenetic Identification of a New Wheat–Psathyrostachys huashanica Keng Translocation Line Resistant to Powdery Mildew

Psathyrostachys huashanica Keng, a wild relative of common wheat with many desirable traits, is an invaluable source of genetic material for wheat improvement. Few wheat–P. huashanica translocation lines resistant to powdery mildew have been reported. In this study, a wheat–P. huashanica line, E24-3-1-6-2-1, was generated via distant hybridization, ethyl methanesulfonate (EMS) mutagenesis, and backcross breeding. A chromosome karyotype of 2n = 44 was observed at the mitotic stage in E24-3-1-6-2-1. Genomic in situ hybridization (GISH) analysis revealed four translocated chromosomes in E24-3-1-6-2-1, and P. huashanica chromosome-specific marker analysis showed that the alien chromosome fragment was from the P. huashanica 4Ns chromosome. Moreover, fluorescence in situ hybridization (FISH) analysis demonstrated that reciprocal translocation had occurred between the P. huashanica 4Ns chromosome and the wheat 3D chromosome; thus, E24-3-1-6-2-1 carried two translocations: T3DS·3DL-4NsL and T3DL-4NsS. Translocation also occurred between wheat chromosomes 2A and 4A. At the adult stage, E24-3-1-6-2-1 was highly resistant to powdery mildew, caused by prevalent pathotypes in China. Further, the spike length, numbers of fertile spikelets, kernels per spike, thousand-kernel weight, and grain yield of E24-3-1-6-2-1 were significantly higher than those of its wheat parent 7182 and addition line 24-6-3-1. Thus, this translocation line that is highly resistant to powdery mildew and has excellent agronomic traits can be used as a novel promising germplasm for breeding resistant and high-yielding cultivars.

Molecular Cytogenetic and Agronomic Characterization of the Similarities and Differences Between Wheat–Leymus mollis Trin. and Wheat–Psathyrostachys huashanica Keng 3Ns (3D) Substitution Lines

Psathyrostachys huashanica Keng (2n = 2x = 14, NsNs) and Leymus mollis Trin. (2n = 4x = 28, NsNsXmXm) are valuable resources for wheat breeding improvement as they share the Ns genome, which contains diverse resistance genes. To explore the behaviors and traits of Ns chromosomes from the two species in wheat background, a series of wheat–P. huashanica and wheat–L. mollis substitution lines were developed. In the present study, line DH109 (F7 progeny of wheat–P. huashanica heptaploid line H8911 × durum wheat Trs-372) and line DM131 (F8 progeny of wheat–L. mollis octoploid line M842 × durum wheat Trs-372) were selected. Cytological observation combined with genomic in situ hybridization experiments showed that DH109 and DM131 each had 20 pairs of wheat chromosomes plus a pair of alien chromosomes (Ns chromosome), and the pair of alien chromosomes showed stable inheritance. Multiple molecular markers and wheat 55K SNP array demonstrated that a pair of wheat 3D chromosome in DH109 and in DM131 was substituted by a pair of P. huashanica 3Ns chromosome and a pair of L. mollis 3Ns chromosome, respectively. Fluorescence in situ hybridization (FISH) analysis confirmed that wheat 3D chromosomes were absent from DH109 and DM131, and chromosomal FISH karyotypes of wheat 3D, P. huashanica 3Ns, and L. mollis 3Ns were different. Moreover, the two lines had many differences in agronomic traits. Comparing with their wheat parents, DH109 expressed superior resistance to powdery mildew and fusarium head blight, whereas DM131 had powdery mildew resistance, longer spike, and more tiller number. Therefore, Ns genome from P. huashanica and L. mollis might have some different effects. The two novel wheat–alien substitution lines provide new ideas and resources for disease resistance and high-yield breeding on further utilization of 3Ns chromosomes of P. huashanica or L. mollis.

Transcriptome-based identification and validation of optimal reference genes for quantitative real-time PCR normalization in Psathyrostachys huashanica

Background: P. huashanica ( Psathyrostachys huashanica ), known as an important resistance resource reservoir, is a rare and endangered plant growing suitably in Huashan mount region and would be urgently exploited in wheat genetic improvements sooner. During the utilization process, different IRGs (internal reference genes) need to be appropriately selected as standards based on biotic and abiotic stress conditions. It is crucial that Real-time RT-qPCR with combination of bioinformatics were adopted to explore the reliable IRGs from transcriptome of P . huashanica.Results: The present work reported new 3 species of IRGs, UBC2 , UBC17, 18S rRNA , which were screened from transcriptome of P. huashanica under biotic and abiotic stress conditions, using RT-qPCR and four algorithms, including geNorm, NormFinder, BestKeeper, and RefFinder, to analyse expression of sixteen candidate reference genes. These genes appear as following 18S rRNA (18S ribosomal RNA), EF1-α (eukaryotic elongation factor 1 alpha), UBC2 (ubiquitin-conjugating enzyme E2-2), UBC17 (ubiquitin-conjugating enzyme E2-17), α-TUB2A (alpha tubulin-2A), β-TUB3 (beta tubulin 3), ADF4 (Actin-depolymerising factor 4), ACTIN (actin), GAPDH (Glyceraldehyde-3-phosphate dehydrogenase), 60SARP (60S acidic ribosomal protein), UBQ (polyubiquitin), SamDC (S-Adenosylmethionine decarboxylase), EIF4A (eukaryotic initiation factor 4A), ARF (ADP-ribosylation factor), HIS1 (histone H1), and HIS2B (histone H2B). Analysis of gene expression demonstrated that the expression of UBC2 gene was most stable under ABA hormone stress, low temperature stress and high temperature stress, similarly, UBC17 gene under IAA hormone stress, salinity stress and drought stress, both UBC17 genes and 18S rRNA genes under abiotic and biotic stress, respectively. The most stable gene was UBC2 gene in the root, UBC17 gene in stem and leaf. In this study, α-TUB2A , UBC and ACTIN genes were verified as the suitable reference genes across all tested samples. To further validate the suitability of the selected reference genes, we evaluated the relative expression of PsaCPK3 (Calcium-dependent protein kinase) and PsaHSP70-1 (heat shock protein 70-1), which are stress-related genes that may be involved in response to adversity.Conclusions: This study has identified a set of the most stable IRGs suiting for RT-qPCR detection of a few target gene expressions from P . huashanica in different experimental conditions. In addition, this study should provide the accuracy information for gene expression analysis in P . huashanica .