[Molecular and cytogenetic identification of Triticum aestivum-Leymus racemosus translocation line T6DL·7LrS].

Leymus racemosus had a high resistant capacity to wheat scab (Fusarum head blight). The transfer of scab resistant gene from L. racemosus to Triticum aestivum is of great significance for broadening the germplasm of wheat resistance. To obtain Triticum aestivum-Leymus racemosus translocation line with scab resistance, we irradiated the pollen of T. aestivum-L. racemosus disomic addition line DA7Lr by 6°Co-γ-rays 1 200 R (100 R/min) prior to pollinating to emasculation T. aestivum cv. Chinese Spring. One plant with one translocation chromosome was detected in the M1 by GISH. The plant with one translocation chromosome was self-pollinated, and at meiotic metaphase I its progenies with two translocation chromosomes were analyzed for chromosome pairing behavior in their pollen mother cells (PMCs). One rod bivalent was observed at meiotic metaphase I, indicating that the plant with two translocation chromosomes was one translocation homozygote. Sequential GISH-FISH analysis, using Oligo-pAs1-2 and Oligo-pSc119.2-2 as probe, translocation line was confirmed as T6DL·7LrS. The translocation line had higher resistance to wheat scab and feasibility to be used as a new source in wheat breeding resistant to scab disease.

Efficient anchoring of alien chromosome segments introgressed into bread wheat by new Leymus racemosus genome-based markers.

BACKGROUND: The tertiary gene pool of bread wheat, to which Leymus racemosus belongs, has remained underutilized due to the current limited genomic resources of the species that constitute it. Continuous enrichment of public databases with useful information regarding these species is, therefore, needed to provide insights on their genome structures and aid successful utilization of their genes to develop improved wheat cultivars for effective management of environmental stresses. RESULTS: We generated de novo DNA and mRNA sequence information of L. racemosus and developed 110 polymorphic PCR-based markers from the data, and to complement the PCR markers, DArT-seq genotyping was applied to develop additional 9990 SNP markers. Approximately 52% of all the markers enabled us to clearly genotype 22 wheat-L. racemosus chromosome introgression lines, and L. racemosus chromosome-specific markers were highly efficient in detailed characterization of the translocation and recombination lines analyzed. A further analysis revealed remarkable transferability of the PCR markers to three other important Triticeae perennial species: L. mollis, Psathyrostachys huashanica and Elymus ciliaris, indicating their suitability for characterizing wheat-alien chromosome introgressions carrying chromosomes of these genomes. CONCLUSION: The efficiency of the markers in characterizing wheat-L. racemosus chromosome introgression lines proves their reliability, and their high transferability further broadens their scope of application. This is the first report on sequencing and development of markers from L. racemosus genome and the application of DArT-seq to develop markers from a perennial wild relative of wheat, marking a paradigm shift from the seeming concentration of the technology on cultivated species. Integration of these markers with appropriate cytogenetic methods would accelerate development and characterization of wheat-alien chromosome introgression lines.

Molecular and cytogenetic identification of Triticum aestivum-Leymus racemosus translocation line T6DL·7LrS / 生物工程学报

Leymus racemosus had a high resistant capacity to wheat scab (Fusarum head blight). The transfer of scab resistant gene from L. racemosus to Triticum aestivum is of great significance for broadening the germplasm of wheat resistance. To obtain Triticum aestivum-Leymus racemosus translocation line with scab resistance, we irradiated the pollen of T. aestivum-L. racemosus disomic addition line DA7Lr by ⁶⁰Co-γ-rays 1 200 R (100 R/min) prior to pollinating to emasculation T. aestivum cv. Chinese Spring. One plant with one translocation chromosome was detected in the M1 by GISH. The plant with one translocation chromosome was self-pollinated, and at meiotic metaphase I its progenies with two translocation chromosomes were analyzed for chromosome pairing behavior in their pollen mother cells (PMCs). One rod bivalent was observed at meiotic metaphase I, indicating that the plant with two translocation chromosomes was one translocation homozygote. Sequential GISH-FISH analysis, using Oligo-pAs1-2 and Oligo-pSc119.2-2 as probe, translocation line was confirmed as T6DL·7LrS. The translocation line had higher resistance to wheat scab and feasibility to be used as a new source in wheat breeding resistant to scab disease.

Impact of wheat-Leymus racemosus added chromosomes on wheat adaptation and tolerance to heat stress.

Adaptation of wheat (Triticum aestivum L.) to high temperatures could be improved by introducing alien genes from wild relatives. We evaluated the responses of wheat-Leymus racemosus chromosome introgression lines to high temperature to determine their potentiality for developing improved wheat cultivars. Introgression lines and their parent Chinese Spring were evaluated in a growth chamber at the seedling stage and in the field at the reproductive stage in two heat-stressed environments in Sudan. Optimum and late planting were used to ensure exposure of the plants to heat stress at the reproductive stage. The results revealed the impact of several Leymus chromosomes in improving wheat adaptation and tolerance to heat. Three lines possessed enhanced adaptation, whereas two showed high heat tolerance. Two addition lines showed a large number of kernels per spike, while one possessed high yield potential. Grain yield was correlated negatively with the heat susceptibility index, days to heading and maturity and positively with kernel number per spike and triphenyl tetrazolium chloride assay under late planting. The findings suggest that these genetic stocks could be used as a bridge to introduce the valuable Leymus traits into a superior wheat genetic background, thus helping maximize wheat yield in heat-stressed environments.

Enhancement of aluminum tolerance in wheat by addition of chromosomes from the wild relative Leymus racemosus.

Aluminum (Al) toxicity is the key factor limiting wheat production in acid soils. Soil liming has been used widely to increase the soil pH, but due to its high cost, breeding tolerant cultivars is more cost-effective mean to mitigate the problem. Tolerant cultivars could be developed by traditional breeding, genetic transformation or introgression of genes from wild relatives. We used 30 wheat alien chromosome addition lines to identify new genetic resources to improve wheat tolerance to Al and to identify the chromosomes harboring the tolerance genes. We evaluated these lines and their wheat background Chinese Spring for Al tolerance in hydroponic culture at various Al concentrations. We also investigated Al uptake, oxidative stress and cell membrane integrity. The L. racemosus chromosomes A and E significantly enhanced the Al tolerance of the wheat in term of relative root growth. At the highest Al concentration tested (200 µM), line E had the greatest tolerance. The introgressed chromosomes did not affect Al uptake of the tolerant lines. We attribute the improved tolerance conferred by chromosome E to improved cell membrane integrity. Chromosome engineering with these two lines could produce Al-tolerant wheat cultivars.