2019 Crop Science Society of America meeting
Improving Our Approach on How We Analyze Turfgrasses for Tolerance to Foliar Shade
by Dominic Petrella and Eric Watkins
Abstract. Turfgrass is often affected by foliar shade such as that from trees and shrubs. This type of shade results in reductions in light quantity and the ratio of red to far-red light (R:FR), both of which can decrease turfgrass quality. The conditions produced by foliar shade are quite variable in nature, and little to no information is available on common reductions in light intensity or commonly found R:FR ratios. A considerable amount of research has evaluated the effects of reduced light quantity on turfgrasses using neutral shade cloth and arbitrary reductions in light quantity; however, most of these studies have not addressed changes in R:FR. Experiments have been performed under real-world foliar shade, but a review of the literature indicated that light quantity is not always monitored and the R:FR ratio is rarely reported. The objective of this research was to evaluate changes in light quantity and the R:FR ratio under foliar shaded turfgrasses in St. Paul MN to better understand how we can approach improving tolerance to foliar shade. The results of a two year study indicate that we may be able to better understand foliar shade sites by 1) taking into account fluctuations in light intensity by collecting data every one minute, 2) examining the number of hours at given light intensities rather than only evaluating the daily light integral, and 3) monitoring R:FR in morning, solar noon, and in the evening.
Unveiling Transcriptome Composition in Hexaploid Hard Fescue (Festuca brevipila) through Pacbio Isoform Sequencing
by Yinjie Qiu, Cory Hirsch and Eric Watkins
Abstract. Hard fescue (Festuca brevipila Tracey, 2n=6x=42) is a fine-textured, cool-season turfgrass that does well under low-input management. Breeding and genetics studies of F. brevipila have been limited due to the complex nature of its hexaploid genome. To advance our knowledge of F. brevipila, we used PacBio isoform sequencing to develop a reference transcriptome of this taxon. Here, we report the F. brevipila reference transcriptome generated from root, crown, leaf, and seed head tissues using 4 SMRT cells. We obtained 59,510 full-length transcripts and further refined them into 38,595 non-redundant full-length transcripts which had a N50 of 2,585 bp. The longest and shortest transcripts were 11,487 and 58 bp, respectively. Transcriptome annotation using NCBI NR protein and Uniprot databases returned 36,075 (93.47%) and 29,670 (76.88%) annotated transcripts, respectively. Finally, we reconstructed the cytochrome P450 gene family phylogenetic tree of F. brevipila to study the effect of propiconazole fungicide on this complex gene family. We found gene expression of CYP709B3 and CYP94C1 had been affected 6 days post the propiconazole treatment. We also identified several gene expression changes in the fatty acid elongation pathway and genes related to histone modifications. Overall, this F. brevipila reference transcriptome will provide geneticists with a foundation to further study this important turfgrass taxon.
Natural Weed Suppression of Crabgrass Varies By Genotype and Field Management Practices
by Jon Trappe, Eric Watkins, Dominic P. Petrella and Florence Sessoms
Abstract. Chewings fescue (Festuca rubra ssp. commutata) has shown potential for natural suppression of crabgrass (Digitaria spp.). Previous work has identified differences among cultivars and species of fine fescues (Festuca ssp) for the amount of crabgrass suppressed. Other work has shown that nutrient status may play an important role in regulating suppression in Chewings fescues. More research is needed to better understand factors controlling variability of crabgrass suppression within Chewings fescue, and how management practices such as mowing and fertilization affect suppression in the field. Therefore the objectives of this experiment were to 1) examine whether weed suppression varies by genotype within an accession or cultivar, and to 2) determine the effect of mowing frequency and nitrogen fertility on allelopathic potential of ‘Radar’ Chewings fescue and ‘Beacon’ hard fescue. For objective 1, 12 genotypes each for a pre-determined low, medium, and highly suppressive Chewings fescue accessions or cultivar were examined for their variability in crabgrass suppression by measuring a reduction in adjacently grown crabgrass biomass within pots in a greenhouse experiment. For objective 2, a split-strip plot design was used in the field to examine the effect of two mowing frequencies (once per week or 3 days per week) stripped across whole plots and two nitrogen fertility (no nitrogen or 46 kg N ha-1 yr-1) split across whole plots have on crabgrass suppression by ‘Radar’ Chewings fescue and ‘Beacon’ hard fescue. Preliminary results indicate that crabgrass suppression varies by genotype within an accession of Chewings fescue and that field management practices may have an impact on crabgrass growth in the field.
2018 Crop Science Society of America meeting
Complete Chloroplast Genome Sequence of Hard Fescue (Festuca brevipila)
by Yinjie Qiu, Cory Hirsch, and Eric Watkins
Abstract. The fine fescue species [Chewings fescue (Festuca rubra ssp. fallax), hard fescue (Festuca brevipila), sheep fescue (Festuca ovina), strong creeping red fescue (Festuca rubra ssp. rubra), and slender creeping red fescue (Festuca rubra ssp. litoralis)] have been shown to perform well in low-input environments in temperate climates. However, due to morphological similarity, species classification of fine fescue species has been challenging. Previous classification of fine fescue species was done through flow cytometry, however, the method is expensive and time consuming. Besides, frequent hybridization events in Poacea species present complications for the use of flow cytometry for species identification. The chloroplast genome has been widely used for several purposes including plant phylogeny determination, species identification, DNA barcoding activities and comparative genomics. Here, we report the first whole chloroplast genome sequence of hard fescue species cultivar ‘Beacon’. We also present the chloroplast genomes of slender red fescue cv. ‘Shoreline’, strong creeping red fescue cv. ‘Navigator II’, Chewings fescue cv. ‘Treazure II’, and sheep fescue cv. ‘Quatro’. We used the genome sequences to reconstruct the phylogeny tree of the fine fescue species with other species within the Festuca-Lolium complex. Finally, we used a comparative genomics approach to characterize the five fine fescues chloroplast genome in order to further develop molecular markers for species identification.
Seed Production of Fine Fescue Turf Grasses in Minnesota
by David R. Herrera, Eric Watkins, Nancy Ehlke, Donn Vellekson, and Garett Heineck
Abstract. The fine fescues include several commercially-relevant perennial grass species of the genus Festuca, specifically, hard fescue (Festuca brevipila), sheep fescue (Festuca ovina), Chewings fescue (Festuca rubra ssp. commutata), strong creeping red fescue (Festuca rubra ssp. rubra), and slender creeping red fescue (Festuca rubra ssp. litoralis). They are reputable low-input turf grasses for temperate climates that persist in drought conditions, shade, and in low-fertility soils. Marketing research provides evidence that consumers place a high value on lower-input turfgrasses; yet, obtaining seed is difficult due to seed inavailability. Most fine fescue seed is produced in Oregon, Canada, and Northern Europe, while Minnesota currently does not have seed production. Our objective was to understand the best fertility and management practices for producing fine fescue seed in Minnesota. In 2016, five fine fescues species were established at three locations in Minnesota (Roseau, Becker, and St. Paul) and then managed under five nitrogen fertility regimes: (1) no nitrogen, (2) 44.8 kg/ha applied in the fall, (3) 89.7 kg/ha applied in the fall, (4) a split application with 22.4 kg/ha applied in both fall and spring, (5) a split application with 44.8 kg/ha applied in both fall and spring. In 2017, at Roseau, which was the highest yielding location, hard fescue ‘MNHD’, Chewings fescue ‘Windward’, and strong creeping red fescue ‘Cindy Lou’, had yields ranging from 630-860 kg/ha. However, individual species responded differently to nitrogen treatments depending on the location; for instance, ‘MNHD’ hard fescue showed an increased yield with higher rates of nitrogen at St. Paul and Roseau, but no such yield increase was seen at Becker. Our data suggests that successful seed production of fine fescue turf grasses should be possible in northern Minnesota.
Identifying and Confirming Natural Weed Suppression in Fine Fescues
by Jon Trappe, Florence Sessoms, Dominic Petrella, Eric Watkins, and Aaron Patton
Abstract. Fine fescues are a group of cool-season turfgrasses used for their low-input requirements. Previous research in field and greenhouse conditions has documented weed suppression by several fine fescue cultivars, but further research is needed to distinguish allelopathy from resource competition. Plant breeders and other turfgrass researchers would benefit from efficient methods by which to identify allelopathic fine fescues. Therefore, we conducted field and greenhouse experiments to screen accessions of hard fescue (Festuca brevipila), Chewings fescue (Festuca rubra ssp. commutata), and strong creeping red fescue (Festuca rubra ssp. rubra) for potential allelopathy. Seven accessions from each fine fescue species were planted in fields historically dominated by crabgrass (Digitaria spp.) in St. Paul, MN and West Lafayette, IN in April 2017. A similar trend in fine fescue accession performance on crabgrass biomass and seedhead reduction was observed between the two locations. These results led to the selection of the best and worst performing accessions (five Chewings fescues and one strong creeping red fescue) for further evaluation in a growth chamber experiment; a pot-based bio-interference study was used to evaluate crabgrass growth responses while growing amongst varying levels of each fine fescue accession. Response variables included chlorophyll content, morphological characteristics, and overall biomass of the crabgrass and fine fescue plants. Preliminary results indicate different levels of weed suppression across the fine fescue accessions tested in both the field and growth chamber experiments. In the field, fine fescue accession had a significant effect on crabgrass germination and emergence, as well as crabgrass biomass and seedhead production. In the bio-interference study, accession significantly affected crabgrass biomass, tiller count, and seedhead production. Further research is needed to better understand the allelopathic mechanism responsible for weed suppression observed in the field and laboratory.
Wear Tolerance of Fine Fescues in Relation to Leaf Tissue Fiber Content
by Hui Chen and James Murphy
Abstract. Fine fescues (Festuca spp.) are low maintenance grasses that could be more widely used if the traffic tolerance of these species were improved. Numerous studies indicated that grass fiber content including cellulose, hemicellulose and lignin may have significant effects on traffic tolerance. Preliminary experiments on turf plots indicated that fine fescues maintaining a uniform cover under wear was positively associated with total cell wall content (NDF) but negatively associated with lignin content (ADL). The objective of this study was to determine the relationship of tissue fiber content with wear/traffic tolerance of fine fescue genotypes. Tiller-plots consisting of 157 Chewings fescue (F. rubra L. subsp. fallax), 155 hard fescue (F. brevipilia), and 149 strong creeping red fescue (F. rubra L. subsp. rubra) genotypes replicated six times were established in field trials at North Brunswick, NJ and St. Paul, MN. During June and July 2018, wear tolerance was evaluated on three replications in North Brunswick, NJ using the Rutgers Wear Simulator (RWS); traffic tolerance was evaluated on three replications in St. Paul, MN using a custom-built golf cart traffic simulator. Assessment of wear/traffic tolerance was based on a 1-10 scale visual rating that considered elements of turf density and bruising (loss of green color) of leave tissue. Sixty genotypes from each species were selected for leaf tissue fiber content measurement. Verdure samples were collected from three non-worn/non-trafficked replications 2 weeks after wear/traffic was terminated. Fresh and dry biomass of sampled genotypes were measured to determine leaf water content. Dried biomass was ground (1-mm) and will be scanned with a near-infrared (NIR) spectrometer and digested to determine total cell wall content (NDF), lignocellulose content (ADF), and cellulose content (ADL). Results will be presented.
The Influence of Nitrogen and Phosphorus Concentrations on the Allelopathic Effects of Festuca Rubra ssp. Commutata
by Dominic Petrella, Florence Sessoms, Jon Trappe, and Eric Watkins
Abstract. Festuca rubra ssp. commutata (Chewings fescue) has been touted to be a potentially allelopathic turfgrass. Chewings fescue roots accumulate and exude the phytotoxin L-m-tyrosine, a structural isomer of the amino acid L-p-tyrosine. In particular, the Chewings fescue cv. ‘Intrigue’ has been said to exude large quantities of L-m-tyrosine. However, while this previous research has shown allelopathic potential among the Chewings fescues, direct observations of allelopathy in the field are lacking. The accumulation and exudation of allelochemicals is influenced by abiotic factors, and soil nutrient status has been shown to regulate allelopathy in other grasses. Because concentrations of soil nitrogen (N) and phosphorus (P) can be quite variable in soils, we hypothesized that the status of these two nutrients could be limiting allelopathy among the Chewings fescues. A Petri plate bioassay to monitor root elongation was implemented using Chewings fescue cv. ‘Intrigue’ plants grown alongside seedlings of a model weed species, Arabidopsis thaliana (ecotype Columbia, Col-0). Modified Hoagland’s nutrient solutions were used to manipulate and test the effect of various levels of N and P within the agar. The quantity of L-m-tyrosine in both the agar and the fescue roots was determined using gas chromatography-mass spectrometry (GC-MS). Our results indicate that Arabidopsis seedling root elongation was inhibited to a significantly greater degree when grown alongside Chewings fescue cv. ‘Intrigue’ relative to being growth alongside additional Arabidopsis plants. This effect was more pronounced with 7.5 and 15 mM nitrogen compared to 3.75 mM, and the addition of 500 µM phosphorus resulted in abnormal gravitropic growth in Arabidopsis roots that was not observed at lower levels of phosphorus. Therefore, these results indicate that nutrient status might play a role in regulating Chewings fescue allelopathy.
Examination of Biological Nitrification Inhibition By a Fine Fescue Root Exudate
by Florence Sessoms, Dominic Petrella, Brian Horgan, Rodney Venterea, and Eric Watkins
Abstract. Nitrogen loss due to nitrate leaching is a problem in many fertilized turfgrass landscapes, and innovative solutions to overcome this challenge are needed. One approach is to use perennial grasses that naturally inhibit nitrification. Biological nitrification inhibition (BNI) is the ability of plant-secreted root exudates to decrease soil nitrification rates and the loss of nitrogen. This occurs due to inhibition of nitrifying bacteria by semi-specific root exuded metabolites. BNI has been previously described in pasture grasses and various cereal crops but never in perennial turfgrass species. Of particular interest are the reduced input turfgrasses including the fine fescues (Festuca sp.), which require lower levels of nitrogen for maintaining improved turfgrass quality. Additionally, Chewings fescue (Festuca rubra ssp. commutata) and strong creeping red fescue (F. rubra ssp. rubra) produce and exude L-m-tyrosine, a known allelochemical, into the rhizosphere. This non-proteogenic amino acid impacts root development of weedy species, and has been shown to reduce bacterial growth. The objective of this research was to determine if Chewings fescue and strong creeping red fescue have the ability to inhibit nitrification due to the biosynthesis of L-m-tyrosine. We tested the potential nitrification inhibition of L-m-tyrosine in a nitrification rate experiment following a modified protocol in which dried soil from St. Paul MN was mixed with a solution containing a phosphate buffer, 1 mM of ammonium sulfate and two concentrations of L-m-tyrosine, 0 and 100 μM, to make a soil slurry. Extractable ammonium and total nitrogen were measured at 12 h and 24 h after addition of L-m-tyrosine. We observed that total nitrogen was significantly lower in the L-m-tyrosine treated soil when compared to the untreated control after 24 h. This bioassay was successfully repeated, and the results suggests that L-m-tyrosine is a putative nitrification inhibitor.
The Effect of Fine Fescue Species and Seeding Rate in No-Mow Areas
by Andrew Hollman, Eric Watkins, and Garett Heineck
Abstract. The use of fine fescues for no-mow areas is increasing among homeowners and turfgrass professionals, along with questions on proper species selection and seeding rates for these areas. Trials were established in 2015 and 2017 at the University of Minnesota in St. Paul to evaluate the effect of species and seeding rate on fine fescue no-mow areas. A single cultivar was used for each fine fescue species:hard fescue (Festuca brevipila), sheep fescue (F. ovina), strong creeping red fescue (F. rubra ssp. rubra), slender creeping red fescue (F. rubra ssp. litoralis), and Chewings fescue (F. rubra ssp. fallax). Each species was planted at a seeding rate of 0.125. 0.25, 0.5. 1, 2, and 3 pure live seed (PLS) per cm2. Species and seeding rate had a significant effect on turf quality, establishment, weed encroachment, lodging, and seed head production. High seeding rates had higher establishment and turfgrass quality while, while low seeding rates had higher seed head density, lodging and weed encroachment. Strong and slender creeping red fescue had the best establishment and lowest weed encroachment while hard and and sheep fescue had the best turf quality and lowest lodging. This data will help consumers choose species and seeding rates depending on the desired aesthetics, use and management inputs of the area.
Evaluating Variation in Shade Tolerance Among Fine Fescue Species
by Dominic Petrella and Eric Watkins
Abstract. Tolerance to shade is a desired trait for cool-season turfgrasses, but improvement in shade tolerance has been challenging. Shade tolerant turfgrass plants, when subjected to both quantitative and qualitative shade, should exhibit negligible etiolation, decreased chlorosis, and efficient carbohydrate partitioning, while maintaining normal amounts of tillering. However, in the field, shade intensity and the duration of shade exposure can be quite variable, making the selection for shade tolerance difficult. Overall, the fine fescue (Festuca ssp.) turfgrasses are said make up one of the most shade tolerant turfgrasses; however, there has been little investigation into the variability for shade tolerance within and among these species. The objective of this research was to evaluate the use of a greenhouse based approach for selecting for improved shade tolerance among the fine fescues. A total of 45 fine fescue entries consisting of hard (Festuca rubra ssp. brevipila), Chewings (F. rubra ssp. commutata), strong creeping red (F. rubra ssp. rubra), and slender creeping red fescue (F. rubra ssp. litoralis) were germinated and grown under vegetative shade conditions in a greenhouse under a photoselective filter that reduced the red to far-red ratio to 0.68, along with a black shade cloth that reduced light quantity by 30%. Etiolation and tillering were measured throughout the experiment, and samples were analyzed for chlorophyll parameters, specific leaf area, and biomass at the conclusion of the experiment. These data were subjected to principal component analysis (PCA), and results show that most of the variation for improved shade tolerance lies within both Chewings and strong creeping red fescue, with Chewings fescues exhibiting the most improved growth under artificial shade.
Determining Optimal Nitrogen Fertility Rates for Reduced-Input Fine Fescue Putting Greens
by Dominic Petrella, Samuel Bauer, Brian Horgan, and Eric Watkins
Abstract. The excessive use of nitrogen fertilizers on golf courses is scrutinized worldwide. For creeping bentgrass (Agrostis stolonifera L.) putting greens in the Midwest U.S., annual nitrogen rates range between 97-293 kg ha-1. Using alternative turfgrasses for greens may help decrease nitrogen use while maintaining turfgrass quality. Fine fescue turfgrasses are used for greens in Europe, and are known for lower nitrogen requirements and reduced input management. However, fine fescues greens have received limited attention in the U.S., and research on the amounts of nitrogen required for a reduced input fine fescue green is lacking. The objective of this study was to determine the lowest possible annual nitrogen fertilizer rate for maintaining a reduced input fine fescue putting green. Chewings fescue (Festuca rubra ssp. commutata), strong creeping red fescue (F. rubra ssp. rubra), slender creeping red fescue (F. rubra ssp. litoralis), hard fescue (F. rubra ssp. trachyphylla), colonial bentgrass (A. capillaris L.), and creeping bentgrass were established in St. Paul, MN. Plots were mowed at 5.1 mm, and were treated with either 0, 48.9, 97.7, or 195.3 kg ha-1 of nitrogen annually beginning May 25th, 2017. Turfgrass quality was assessed visually, using digital images, and using NDVI. During the first year of this study, Chewings and slender creeping red fescue maintained the highest quality of the fine fescues, and also maintained high quality at the low nitrogen rates when compared to both bentgrass species. During year two, the occurrence of summer patch disease (Magnaporthe sp.) resulted in a large decline in quality for all the fine fescues, but Chewings fescue plots were less effected overall. When managing a reduced input putting green, both Chewings and slender creeping red fescue may be suitable alternatives to creeping bentgrass when low nitrogen rates are used, but an active disease management program will be required.