No description available.

Most professional turf in Virginia is comprised of bermudagrass (Cynodon dactylon L.) or (Cynodon dactylon x C. transvaalensis Burtt Davy) as a monoculture in summer and overseeded with perennial ryegrass (Lolium perenne L.) (PR) in winter, during bermudagrass dormancy. Two transitions are required in an overseeding program, fall establishment of PR and spring control of PR. During each transition, turf quality suffers as one grass dies or enters dormancy while another grass is promoted to fill voided areas. Field studies at various locations in Virginia were conducted to investigate methods of improving spring and fall transition. Bermudagrass green cover in August was influenced by duration of PR competition variably between three bermudagrass cultivars. For example, "Midiron", "Patriot", and "Riviera" bermudagrass required 218, 139, and 327 cumulative growing degree days at base 18.3 C (GDD) to reach 95% cover. Bermudagrass biomass was also positively correlated with increasing duration of noncompetitive GDD. Total nonstructural carbohydrates were not correlated to duration of PR competition. Novel application methods were invented and tested at Virginia Tech. Drip, sponge, and strip application methods were used to create patterns of PR control using selective herbicides. Controlling a portion of PR with these methods maintained acceptable turfgrass quality throughout the spring transition and improved bermudagrass cover 12 to 20%, speeding transition by 20 or more days. Efforts to improve PR establishment in dense bermudagrass suggest chemicals that injure existing bermudagrass can improve PR establishment, but cause unacceptable turf discoloration. Mechanical methods to disrupt the bermudagrass canopy had less effect on PR establishment than chemical treatments. / Master of Science

In the United Kingdom and Ireland, a major percentage of fertilized agricultural area is devoted to grasslands, which helps to support the associated milk and beef production industries. In temperate grasslands, perennial ryegrass (L. perenne) is the major forage grass and this species is particularly suitable as a forage grass due to its high yield and digestibility, when compared with other species. However, perennial ryegrass is not well adapted to abiotic stress conditions which are likely to occur in its natural environment. Some of the abiotic stress factors which have significant impacts on plant growth and development include water and nutrient availability. Therefore, this project set out to unravel some of the mechanisms involved in the adaptation of perennial ryegrass to limited water, phosphorous and nitrogen. In order to understand the metabolic mechanisms acting in response to these stresses, metabolite profiling was performed using GC-MS. Furthermore, for the water- and phosphorous-limitation studies this approach was complemented with transcript analysis.In order to study water-limitation a hydroponics system supplemented with polyethyleneglycol (PEG) was used to induce water-limitation for a period of one-week. A clear difference in the metabolic profiles of the leaves of plants grown under water stress was observed. Differences were principally due to a reduction in fatty acid levels in the more water stress-susceptible genotype Cashel and an increase in sugars and compatible solutes in the drought-tolerant PI 462336 genotype. Sugars exhibiting a significant increase included, raffinose, trehalose, glucose, fructose and maltose. Raffinose was identified as the metabolite exhibiting the largest accumulation under water-stress in the more tolerant genotype and may represent a target for engineering superior drought tolerance or form the basis of marker-assisted breeding in perennial ryegrass. The metabolomics approach was combined with a transcriptomics approach in the water stress tolerant genotype PI 462336 which identified genes in perennial ryegrass that were regulated by this stress.The characterization of the response to phosphorus-limitation was performed in a hydroponics system containing two solutions with different levels of phosphorus. Samples were collected from the roots and leaves of two genotypes 24 hours after being exposed to stress. Internal phosphate concentrations were reduced and significant alterations were detected in the metabolome and transcriptome of two perennial ryegrass genotypes. Results indicated a replacement of phospholipids with sulfolipids in response to P deficiency and that this occurs at the very early stages of P deficiency in perennial ryegrass. Additionally, the results suggested the role of glycolytic bypasses and the re-allocation of carbohydrates in response to P deficiency The characterization of the metabolic response of L. perenne leaves to different levels of nitrogen supply was performed for seven different genotypes with variability in the regrowth response rate to nitrogen supply in a hydroponics system. This facilitated the identification of common mechanisms of response between genotypes to nitrogen. The metabolic response observed included modifications of the lipid metabolism, as well as alterations of secondary aromatic metabolite precursors in plants exposed to nitrogendeficit. In contrast, plants grown in a nitrogen saturated media appeared to modify to some extent the metabolism of ascorbate. Additionally, it was found that amino acid levels increased with increasing concentrations of nitrogen supplied. This study suggested that the involvement of secondary metabolism, together with lipid and ascorbate metabolism, is of crucial importance in the early-adaptation of perennial ryegrass plants to different levels of nitrogen supply.

Fungal endophytes of the genus Neotyphodium form stable symbiotic associations, with grasses, that are symptomless and generally considered to be mutualistic. The benefits that these fungi confer to their grass hosts are exploited in pastoral agriculture systems. The production of a range of secondary metabolites, specifically alkaloids including peramine and ergovaline can give their host plants an ecological advantage in certain environments. Neotyphodium endophytes are asexual and have lost the ability to transfer horizontally between hosts making seed transmission a vital feature of the association. This thesis reports the occurrence of phenotypically different perennial ryegrass plants (Lolium perenne) in a population infected with Neotyphodium lolii. Here we show that the change in the plants is directly attributable to a variant endophyte that they host. Isolation of the variant endophyte reveals a change in colony growth compared to the wild-type resident endophyte in the population, which has a white and cottony phenotype. Colonies of the variant endophyte are smaller than wild-type colonies and mucoid, with hyphal filaments forming aggregates. Evidence shows that the switch between colony morphologies occurs at a very high frequency, is reversible, and appears to be environmentally induced. This suggests that the switching phenomenon involves gene regulation rather than mutation. When endophyte-free plants are infected, with either white and cottony (wild-type) or mucoid (variant) fungal colonies, they assume a morphology consistent with the state of the fungus at the time of inoculation, that is normal or dwarfed, respectively. In addition, re-isolation of endophyte from either normal or dwarfed plants always yields white and cottony or mucoid colonies, respectively, suggesting that the host environment stabilizes the state of the fungus. Proteomic profiling revealed differences in protein expression between plants infected with either the wild-type or mucoid fungus. Furthermore, host plants containing the mucoid fungus have never flowered or produced seed. Thus, if this change in the fungal symbiont occurs in a competitive natural environment the mucoid fungus and its host plant may not persist beyond the first generation. This thesis provides insights into the plastic nature of fungal endophyte/grass symbiota and discusses possible mechanisms for the observed morphological switching in culture and host dwarfing.

No description available.

<p>PGP mikroorganizmi (Plant Growth Promoting) su predmet mnogobrojnih istraživanja, čiji je glavni cilj pronalaženje adekvatnog načina njihove primene u poljoprivredi, hortikulturi, &scaron;umarstvu i za&scaron;tititi životne sredine. Cilj ovih istraživanja bio je izolacija i karakterizacija mikroorganizama sa PGP svojstvima iz rizosfere engleskog ljulja, ispitivanje sposobnosti njihovog preživljavanja nakon uno&scaron;enja u zemlji&scaron;te, kao i praćenje uticaja njihove primene na parametre prinosa i mikrobiolo&scaron;ku aktivnost u rizosferi biljke. Karakterizacija izolata roda Pseudomonas, Bacillus i Streptomyces obuhvatila je određivanje fiziolo&scaron;kih, biohemijskih i PGP osobina. Uticaj introdukcije odabranih izolata i gljive Trichoderma asperellum na brojnost i mikrobiolo&scaron;ku aktivnost u rizosferi engleskog ljulja, određivan je standardnim metodama na selektivnim hranljivim podlogama, a dehidrogenazna aktivnost spektrofotometrijskom metodom. U laboratorijskim uslovima ispitivan je efekat primene izolata na klijavost, dužinu korenka i stabaoca klice semena engleskog ljulja. U toku godine, uzimana su tri otkosa i pri tome su određivani dužina nadzemnog dela i korena biljke (cm) i prinos zelene i suve materije nadzemnog dela biljke po otkosu (t/ha). Na osnovu morfolo&scaron;kih, fiziolo&scaron;ko-biohemijskih, kao i PGP osobina koje su izolati pokazali, te na osnovu rezultata mnogobrojnih dosada&scaron;njih istraživanja, može se zaključiti da izolati P1 i P9 pripadaju vrsti Pseudomonas putida, izolat P12 Pseudomonas fluorescens, izolati B1, B3 i B6 vrsti Bacillus subtilis, a izolati A1, A2, A3 rodu Streptomyces. Brojnost pojedinih sistematskih i fiziolo&scaron;kih grupa mikroorganizama kao i enzimatska aktivnost u rizosferi engleskog ljulja, zavisila je od primenjenih inokulanata. Primena izolata Pseudomonas sp. P12 pozitivno je uticala na povećanje ukupnog broja mikroorganizama, brojnost gljiva, aminoheterotrofa i aktinomiceta. Izolat Bacillus sp. B1 uticao je na povećanje ukupnog broja mikroorganizama, brojnosti gljiva i azotobaktera. Primena izolata Streptomyces sp. A3 dovela je do povećanja broja aktinomiceta i oligonitrofila, dok je primena Trichoderma asperellum uticala pozitivno na povećanje broja aminoheterotrofa i azotobaktera. Primena izolata Pseudomonas sp. P12 i Streptomyces sp. A3 imala je najveći efekat na dehidrogenaznu aktivnost. Inokulacija je imala pozitivan uticaj na klijavost, svežu i suvu masu biljke, visinu i dužinu korena biljaka. Primena gljive Trichoderma asperellum i izolata Streptomyces sp. A3 delovala je pozitivno na klijavost, dužinu korenka i stabaoca klice. U proseku, najbolji efekat na prinos sveže i suve materije, kao i na visinu nadzemnog dela i dužinu korena biljke, imala je primena izolata Pseudomonas sp.P12 i Bacillus sp. B1.U proizvodnji krmnih trava mikroorganizmi jo&scaron; nisu na&scaron;li značajniju praktičnu primenu iako je veći i kvalitetniji prinos jedan od ciljeva stočarske proizvodnje. Rezultati ovih istraživanja su pokazali da se primenom mikroorganizama mogu postići pozitivni efekti i u proizvodnji engleskog ljulja. Zbog toga je veoma značajno da se vr&scaron;e dalja ispitivanja uzajamnog odnosa primenjenih mikroorganizama i engleskog ljulja u poljskim uslovima, kako bi se optimizirao način i vreme primene inokulanata</p> / <p>PGP microorganisms (Plant Growth Promoting) have been the subject of many research projects, whose main goal is to find appropriate methods of their use in agriculture, horticulture, forestry and environmental protection. The aim of this study is the isolation and characterization of microorganisms with PGP characteristics from the rhizosphere of perennial ryegrass, testing their ability to survive after entering the soil, and monitoring the impact of their application on yield parameters and microbial activity in the rhizosphere of plants. Characterization of Pseudomonas, Bacillus and Streptomyces included determination of the physiological, biochemical and PGP characteristics. Impact of the introduction of selected isolates and fungi Trichoderma asperellum on quantity and microbial activity in the rhizosphere of ryegrass was determined by using the standard method of selective media; dehydrogenase activity by the spectrophotometric method. The effects of the implementation of isolates on germination, seedling length sprouts seeds of perennial ryegrass were studied under laboratory conditions. During the year, three cuttings were taken. At each of the three cuttings, length of stem and roots of plants (cm) and yields of fresh and dry matter of the plant (t / ha) were measured.<br />Based on morphological, physiological and biochemical characteristics and PGP characteristics observed in the isolates, and based on the results of many previous studies, it can be concluded that (1) P1 and P9 isolates belong to the species Pseudomonas putida, (2)Pseudomonas fluorescens P12 isolate, isolates of B1, B3, B6, belong to the species Bacillus subtilis, and (3) A1, A2 and A3 isolates belong to the ordo Streptomyces. The quantity of systematic and physiological groups of microorganisms and enzymatic activity in the rhizosphere of ryegrass depended on the applied inoculants. Application of Pseudomonas sp. P12 had positive effects on increasing the total number of microorganisms, fungi, aminoheterotrophs and actinomycetes. Isolate Bacillus sp. B1 affected the increase of the total number of micro-organisms in the fungi and Azotobacter. Application of Streptomyces sp. isolates A3 led to an increase in the number of actinomycetes and oligonitrophyls, while the application of Trichoderma asperellum had positive impact on increasing the number aminoheterotrophs and Azotobacter. Application of Pseudomonas sp. P12 and Streptomyces sp. A3 had the greatest effect on dehydrogenase activity. Inoculation had a positive effect on germination, fresh and dry weight of plant, height and rootlength of plants. Introduction of fungus Trichoderma asperellum and Streptomyces sp. A3 isolate acted positively on germination, length of seedling of germs. On average, the best effects on the yield of fresh and dry matter, the height of the stem of the plant and the length of the root were attained by the application of Pseudomonas sp.P12 and Bacillus sp. B1 isolates. Microorganisms have not yet found significant practical use in the production of forage grasses, even though more qualitative yield has been sought in livestock production. The results of this study demonstrate that positive results in the production of perennial ryegrass can be achieved by the use of microorganisms. Therefore, it is very important to carry out further studies of the relationship between applied microorganisms and ryegrass under field conditions in order to optimize the method and time of application of inoculants.</p>

Cool season perennial grasses are the foundation of equine nutrition in the transition zone. The objective of this study was to evaluate forage quality using ADF, NDF, IVTDMD, CP, WSC, and ESC and changes in vegetative swards seasonally, diurnally, across species (Kentucky bluegrass, tall fescue, orchardgrass, and perennial ryegrass) and cultivar. This study was conducted in 2015 and 2017 and plots were maintained vegetatively with two to four week mowing. Morning and afternoon sample collection occurred monthly during the growing season. Samples were flash frozen; freeze dried, ground, and scanned using Near Infrared Reflectance Spectroscopy (NIRS) to predict forage quality. There was a significant year effect; therefore year was analyzed separately. Generally, ADF and NDF were highest for Kentucky bluegrass (30 and 52%), lowest for perennial ryegrass (25 and 46%), and tall fescue and orchardgrass were inconsistent. Crude protein was variable across species and season, ranging 10 to 25%. ADF and NDF concentrations were higher in the morning; IVTDMD, WSC, and ESC were higher in the afternoon; and CP was similar diurnally. In conclusion, forage quality in vegetative cool season grass pastures was sufficient to meet the nutritional needs of most equines, but varied seasonally, diurnally, across species, and cultivar.

The aims of this study were to develop a genetic linkage map of perennial ryegrass, identify quantitative trait loci (QTL) for herbage and seed production traits, and to identify DNA markers associated with QTL for use in marker-assisted selection (MAS). Major traits identified for herbage production were leaf elongation rate (LER), leaf lamina length (LL), tiller number (TN) and tiller weight (TW), and for increased seed production were seed yield per head (SdYH), reproductive tiller number (RT), reproductive tillers with matured heads (TMH), florets per head (FH), spikelets per head (SH), florets per spikelet (FS), floret site utilization (FSU) and seed weight (TSW). A genetic linkage map spanning 582 centimorgans (cM) was constructed with EST-SSR (simple sequence repeat markers derived from expressed sequence tags) and used to identify QTL for herbage dry weight (DW) and seed yield per plant (SdYP), and their key component traits. Significant genotype by environment effects were encountered for herbage yield, with fewer QTL identified in spring than in autumn. For some traits, ranking of genotypes differed greatly between seasons and different QTL were identified. QTL for DW were identified on linkage groups (Lg) 1 and 6. The QTL on Lg 6 co-located with QTL for TN, while that on Lg 1 co-located with LER and LL. Markers at Lg 1 QTL (qDW-03-1.1) may be more useful for increasing herbage production by MAS because selection for high LER and long LL has been suggested to increase herbage production in perennial ryegrass. QTL for SdYP were identified on Lg 2 and Lg 6. The QTL on Lg 6 co-located with QTL for SdYH, FSU and TSW, while that on Lg 2 co-located with FH, SH and FS. For seed production, markers at Lg 6 QTL (qSdYP-03-6) may be very useful because this QTL co-located with QTL for SdYH, FSU and TSW, and SdYH has been identified previously as a key selection criterion for increasing seed yield. Marker-trait validation confirmed markers pps0495 and pps0698 identified by QTL analysis to be potentially useful for selecting for fast leaf appearance and long LL, respectively, in perennial ryegrass.

Appendix content (raw data and statistics; sequences) unavailable online, but available with print copy / Epichloë/Neotyphodium endophytes are a group of clavicipitaceous fungi that form symbiotic associations with temperate grasses. The asexual N. lolii form asymptomatic mutualistic associations with ryegrass whereas the sexual E. typhina behaves similar to a mutualist during the vegetative phase of plant growth but switches to epiphytic growth and formation of an external stroma upon development of the floral inflorescence. The aim of this project was to study the metabolic interaction between these endophytes and their perennial ryegrass host. The role of endophyte thiamine biosynthesis in host colonisation and stroma development was chosen, because of the key role this coenzyme plays in primary cellular metabolism and because thiamine biosynthetic genes are induced in several fungal-plant interactions. The orthologue (thil) of Saccharomyces cerevisiae THI4 was isolated from N. lolii and E. typhina by PCR using degenerate primers designed to conserved regions of known thiazole biosynthetic genes. This gene is expressed in planta and in culture, and is alternatively spliced, with distinct patterns of the isoforms expressed under different nutritional conditions. Mutant with a deletion in the E. typhina thil gene was constructed and shown to have reduced hyphal density and branching compared to the wild-type on defined media lacking thiamine. Both thiamine and thiazole complemented this defect. Artificial inoculation of the mutants into plants showed that the thil mutant retained the ability to colonise the perennial ryegrass host and form stromata. However, the mutant had some differences in host colonisation and growth, including reduced hyphal branching and reduced detrimental effects on the host. In addition, glycogen-like deposits, which were abundant in the wild-type hyphae, were not evident in the mutants. Unexpectedly, both the thil mutant and wild-type strains formed some stromata on vegetative tissue. Electron microscopic examination revealed that the cells of epiphytic hyphae found on the vegetative tillers typically were enlarged, lacking in cytoplasm and highly vacuolated, an ultrastructure similar to that found for hyphae growing in reproductive tillers. The mutants retained the ability to form conidia on the outer layer of the stromata. Extensive vascular colonisation and hyphal ramification in the mesophyll were common characteristics of stromata bearing regions. Although the morphology and ultrastructure of stromata formed on vegetative tillers is very similar to those on reproductive tillers, one significant difference was the presence of abundant glycogen-like deposits in hyphae of vegetative tillers. Furthermore, there were dramatic differences in the levels of glycogen-like deposits in hyphae in different regions of the vegetative tillers, indicating that the energy demand changes during stroma development. This is the first report of E. typhina forming stromata on non-inflorescence tillers.

No description available.