Search

Cynodon Rich. is one of the major turfgrass and forage genera in warmer climates of the United States and other world regions. New cultivars of Cynodon spp. are often developed by hybridization of a limited number of accessions of two species—C. transvaalensis Burtt Davy and C. dactylon (L.) Pers.—or by selection from existing cultivars. This may lead to an erosion of diversity. Several other species of this genus also exhibit desirable traits, and they could be used in the development of new cultivars to increase the range of genetic variation. In this study, the genetic diversity of seven Cynodon species was assessed using Diversity Array Technology sequencing (DArTseq). This technology is capable of identifying single nucleotide polymorphism (SNP) markers with no prior DNA sequence information. The 85 analyzed accessions showed considerable genetic variation and formed several distinct groups based on the degree of relatedness. However, none of these groups were comprised of only accessions of the same species, suggesting that DNA marker groupings are not well in agreement with botanical classification for this genus. The identification of species‐specific SNP markers provides an additional tool for species reclassification and may clear up pedigrees of some established cultivars. [ABSTRACT FROM AUTHOR]

Turf-type tall fescue (Festuca arundinacea Schreb.) germplasm available both commercially and in cultivar trials is surprisingly similar in quality and performance. To test genetic diversity within this germplasm, Diversity Arrays Technology (DArT) was used to detect DNA polymorphism among 93 entries from the 2006 National Turfgrass Evaluation Program tall fescue test in Riverside, CA. Based on the analysis of 190 polymorphic DArT markers, we found little variability in the turf-type cultivars. These data are in agreement with field observations showing very few distinguishable differences in turf quality among the entries, with the exception of 'Kentucky-31', a forage-type standard entry. This cultivar ranked lowest for turf quality. The 93 entries were then compared with 14 forage-type and four turf-type accessions collected worldwide, further demonstrating narrow diversity among the entries and overall lower genetic diversity among turf-types relative to forage-types. Such low genetic polymorphism of turf-type genotypes indicates a very close relationship regardless of the origin. It may have been caused by either a severe genetic bottleneck in the conversion of germplasm from forage to turfgrass use, or by extensive sharing of germplasm. This indicates an urgent need to rapidly broaden the genetic diversity in commercial germplasm of turf-type tall fescue. [ABSTRACT FROM AUTHOR]

A 10‐yr, four‐phase collaborative effort among three universities was conducted to develop new hybrid zoysiagrasses (Zoysia spp. Willd.) with improved turf quality, winter hardiness, and pest resistance in comparison to commercial zoysiagrass cultivars, especially 'Meyer' (Z. japonica Steud.). In Phase 1, breeding efforts produced 2,858 new progeny that were evaluated for 2 yr across three sites. In Phase 2, only 60 (2%) of 2,858 progeny were selected for advancement to 10 replicated multiyear field trials (Phase 3). Phase 3 revealed 10 promising progeny (assigned DALZ numbers) that required further intensive field and laboratory testing in Phase 4. Phase 4 revealed differences in establishment rate, and DALZ 1701, 1702, 1707, and 1810 had moderate‐to‐good turf performance across seven sites, whereas DALZ 1808 had similar or slightly lower performance. Meyer consistently performed poorly, and 'Innovation', a recently released hybrid cultivar, had poor‐to‐moderate performance in comparison to the experimental genotypes, which illustrates the improvements achieved in zoysiagrass breeding in the last 10 yr. Freeze tolerance (LT50, lethal temperature killing 50% of the plants) ranged from −9.8 °C (Diamond) to −14.1 °C (DALZ 1812) with a mean of −12.5 °C. Evidence of large patch [Rhizoctonia solani Kühn, anastomosis Group (AG) 2‐2 LP] in the top 10 DALZ genotypes was 15 to 40% lower than Meyer on several dates. Results indicate that there are multiple genotypes for potential release in the future with improved turf color, winter hardiness, freeze tolerance, large patch resistance, and finer leaf texture suitable for USDA plant hardiness zones ranging between 5b and 8a. Core Ideas: Multidisciplinary, systematic breeding efforts effectively improve zoysiagrass.Intra‐ and interspecific hybridization introgressed superior turf traits.Multiple options exist for potential zoysiagrass release for a variety of climates. [ABSTRACT FROM AUTHOR]

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 FROM AUTHOR]

Broadening the genetic pool of crop species by wide hybridization is an established practice in plant breeding. Festuca × Lolium hybrids (Festulolium [FL]) are already established as commercial forage grasses around the world. By recurrent selection for drought and heat tolerance we developed turf-type populations of FL with increased stress tolerance. This improvement appeared associated with the presence of an introgression of meadow fescue [Festuca pratensis (Huds.) P. Beauv.] chromatin on chromosome 3 of perennial ryegrass (Lolium perenne L.). To determine if deeper and more extensive root characteristics were responsible for increased stress tolerance, a greenhouse study was conducted on FL both with and without the introgression, parental controls, and tall fescue (F. arundinacea Schreb.). In two experiments in sand-filled tubes, meadow fescue (MF) produced the deepest roots, most root biomass, and highest root:shoot ratio; FL and perennial ryegrass (PR) were intermediate while tall fescue (TF) ranked at or near the bottom for these traits. The results suggested that drought tolerance in FL was not a consequence of altered root depth or biomass. In a 2-yr field study of drought tolerance at deficit irrigation (50-70% ET0), turf quality of FL and PR was significantly greater compared to the fescues; FL populations appeared to offer greater turf quality during drought conditions than the fescues, but they did not differ from PR itself. In only 1 yr were mature TF stands equal to PR and FL in recovery rates. While the actual mechanism is still obscure, it appears that, with additional breeding and selection, FL hybrids have the potential to withstand water deficit at least as well as TF, while providing better turf quality. [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]

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. [ABSTRACT FROM AUTHOR]