Search

Abstract: Kikuyugrass [Cenchrus clandestinus (Hochst. ex Chiov.) Morrone (= Pennisetum clandestinum Hochst. ex Chiov.)] is a warm‐season grass native to Africa. It was introduced into the United States as forage in Hawaii and for erosion control in California. Kikuyugrass is considered invasive and currently is on the USDA's noxious weed list. Since complete eradication is difficult, it has become the primary species on several golf courses, athletic fields, and lawns. Kikuyugrass possesses exceptional quality with considerable cultural inputs, and little or no winter dormancy compared with other warm‐season turfgrasses. With breeding efforts directed specifically at reducing aggressiveness and improving texture, thus reducing inputs, it could become a valuable turf‐type species in coastal and inland California. The genetic diversity of kikuyugrass was investigated using single nucleotide polymorphism (SNP) and silicoDArT (presence or absence) markers revealed by the Diversity Arrays Technology sequencing (DArTseq) platform. Accessions were sampled throughout California, Hawaii, and Australia, both from natural stands and various collections. Among the 254 accessions tested, two distinct groups were discovered, and there was no geographic pattern to this differentiation. The overall level of SNP polymorphism was low (polymorphic information content [PIC] average = .33, PIC median = .38). Most (76%) of the observed genetic variation was within populations, whereas 24% was among populations. Average genetic distances within populations ranged from 0.09 to 0.16, whereas distances among populations ranged from 0.13 to 0.36. Accessions from Hawaii and Australia were the most diverse; however, a detectable level of genetic diversity of kikuyugrass also exists in California, mostly because of the past introductions from Australia.

Abstract Background Grasses are among the most important and widely cultivated plants on Earth. They provide high quality fodder for livestock, are used for turf and amenity purposes, and play a fundamental role in environment protection. Among cultivated grasses, species within the Festuca-Lolium complex predominate, especially in temperate regions. To facilitate high-throughput genome profiling and genetic mapping within the complex, we have developed a Diversity Arrays Technology (DArT) array for five grass species: F. pratensis, F. arundinacea, F. glaucescens, L. perenne and L. multiflorum. Results The DArTFest array contains 7680 probes derived from methyl-filtered genomic representations. In a first marker discovery experiment performed on 40 genotypes from each species (with the exception of F. glaucescens for which only 7 genotypes were used), we identified 3884 polymorphic markers. The number of DArT markers identified in every single genotype varied from 821 to 1852. To test the usefulness of DArTFest array for physical mapping, DArT markers were assigned to each of the seven chromosomes of F. pratensis using single chromosome substitution lines while recombinants of F. pratensis chromosome 3 were used to allocate the markers to seven chromosome bins. Conclusion The resources developed in this project will facilitate the development of genetic maps in Festuca and Lolium, the analysis on genetic diversity, and the monitoring of the genomic constitution of the Festuca × Lolium hybrids. They will also enable marker-assisted selection for multiple traits or for specific genome regions.

Wetting agents have been reported to alleviate localized dry spot and save water while maintaining turf quality at an acceptable level. However, limited research has been conducted on comparing the effects of different wetting agent products. A study was conducted from May to October in 2018 and 2019 in Riverside, CA to evaluate 10 wetting agent treatments on performance of 'Tifway II' hybrid bermudagrass [Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt Davy] under deficit irrigation at three reference evapotranspiration (ETo) levels: 45, 55, and 65% ETo. Ten wetting agent treatments were selected based on manufacturer recommendations. Plots were evaluated for visual turf quality, percent green cover (PGC), dark green color index, normalized difference vegetation index (NDVI), soil volumetric water content, soil moisture variability, and proline content in dry-leaf samples. Wetting agent treatments improved turf quality and PGC, and decreased soil moisture variability. Moreover, up to 16% increase in soil moisture levels was observed on treated vs. untreated control. No differences were observed for NDVI, proline content in leaves, or fall color retention. Overall, soil moisture variability declined in 2019, and turf quality improved in both years when any wetting agent treatment was applied, and only minor differences were observed among wetting agent treatments evaluated in this study. Other physiological indicators and soil rootzone characteristics are needed to gauge the effects of wetting agents under deficit-irrigated turfgrass. [ABSTRACT FROM AUTHOR]

Abstract Background Grasses are among the most important and widely cultivated plants on Earth. They provide high quality fodder for livestock, are used for turf and amenity purposes, and play a fundamental role in environment protection. Among cultivated grasses, species within the Festuca-Lolium complex predominate, especially in temperate regions. To facilitate high-throughput genome profiling and genetic mapping within the complex, we have developed a Diversity Arrays Technology (DArT) array for five grass species: F. pratensis, F. arundinacea, F. glaucescens, L. perenne and L. multiflorum. Results The DArTFest array contains 7680 probes derived from methyl-filtered genomic representations. In a first marker discovery experiment performed on 40 genotypes from each species (with the exception of F. glaucescens for which only 7 genotypes were used), we identified 3884 polymorphic markers. The number of DArT markers identified in every single genotype varied from 821 to 1852. To test the usefulness of DArTFest array for physical mapping, DArT markers were assigned to each of the seven chromosomes of F. pratensis using single chromosome substitution lines while recombinants of F. pratensis chromosome 3 were used to allocate the markers to seven chromosome bins. Conclusion The resources developed in this project will facilitate the development of genetic maps in Festuca and Lolium, the analysis on genetic diversity, and the monitoring of the genomic constitution of the Festuca × Lolium hybrids. They will also enable marker-assisted selection for multiple traits or for specific genome regions.

The analysis of large genomes is hampered by a high proportion of repetitive DNA, which makes the assembly of short sequence reads difficult. This is also the case in meadow fescue (Festuca pratensis), which is known for good abiotic stress resistance and has been used in intergeneric hybridization with ryegrasses (Lolium spp.) to produce Festulolium cultivars. In this work, we describe a new approach to analyze the large genome of meadow fescue, which involves the reduction of sample complexity without compromising information content. This is achieved by dissecting the genome to smaller parts: individual chromosomes and groups of chromosomes. As the first step, we flow sorted chromosome 4F and sequenced it by Illumina with approximately 50 × coverage. This provided, to our knowledge, the first insight into the composition of the fescue genome, enabled the construction of the virtual gene order of the chromosome, and facilitated detailed comparative analysis with the sequenced genomes of rice (Oryza sativa), Brachypodium distachyon, sorghum (Sorghum bicolor), and barley (Hordeum vulgare). Using GenomeZipper, we were able to confirm the collinearity of chromosome 4F with barley chromosome 4H and the long arm of chromosome 5H. Several new tandem repeats were identified and physically mapped using fluorescence in situ hybridization. They were found as robust cytogenetic markers for karyotyping of meadow fescue and ryegrass species and their hybrids. The ability to purify chromosome 4F opens the way for more efficient analysis of genomic loci on this chromosome underlying important traits, including freezing tolerance. Our results confirm that next-generation sequencing of flow-sorted chromosomes enables an overview of chromosome structure and evolution at a resolution never achieved before. [ABSTRACT FROM AUTHOR]

The analysis of large genomes is hampered by a high proportion of repetitive DNA, which makes the assembly of short sequence reads difficult. This is also the case in meadow fescue (Festuca pratensis), which is known for good abiotic stress resistance and has been used in intergeneric hybridization with ryegrasses (Lolium spp.) to produce Festulolium cultivars. In this work, we describe a new approach to analyze the large genome of meadow fescue, which involves the reduction of sample complexity without compromising information content. This is achieved by dissecting the genome to smaller parts: individual chromosomes and groups of chromosomes. As the first step, we flow sorted chromosome 4F and sequenced it by Illumina with approximately 50 × coverage. This provided, to our knowledge, the first insight into the composition of the fescue genome, enabled the construction of the virtual gene order of the chromosome, and facilitated detailed comparative analysis with the sequenced genomes of rice (Oryza sativa), Brachypodium distachyon, sorghum (Sorghum bicolor), and barley (Hordeum vulgare). Using GenomeZipper, we were able to confirm the collinearity of chromosome 4F with barley chromosome 4H and the long arm of chromosome 5H. Several new tandem repeats were identified and physically mapped using fluorescence in situ hybridization. They were found as robust cytogenetic markers for karyotyping of meadow fescue and ryegrass species and their hybrids. The ability to purify chromosome 4F opens the way for more efficient analysis of genomic loci on this chromosome underlying important traits, including freezing tolerance. Our results confirm that next-generation sequencing of flow-sorted chromosomes enables an overview of chromosome structure and evolution at a resolution never achieved before. [ABSTRACT FROM AUTHOR]