<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.

Some aspects of the presence of systemic endophytic fungi in agriculturally important New Zealand grasses were studied in relation to plant breeding. Seedling resistance to adult Argentine stem weevil feeding in perennial ryegrass, Italian ryegrass and tall fescue was found to be related to the presence of their respective Acremonium endophytes in the seed rather than to plant genetic resistance. In addition a study of perennial ryegrass revealed that this resistance was independent of endophyte viability. The seedling resistance conferred by the endophyte of Italian ryegrass was found to be beneficial for field establishment. This endophyte differs from that in perennial ryegrass and tall fescue in that it does not confer resistance to Argentine stem weevil on mature plants, but only on seedlings. The extent of plant genetic seedling tolerance to adult Argentine stem weevil feeding was limited to broad inter-specific differences, with tall fescue more tolerant than perennial ryegrass and both of these more tolerant than Italian ryegrass. This ranking corresponds with previous observations on feeding preference on mature plants. A study of factors affecting the concentration of endophyte mycelia in infected seed of perennial ryegrass revealed that plant genetic factors had little effect. The major factors studied were: 1) the endophyte concentration in the maternal parent plant directly influenced the endophyte concentration in the seed. 2) nitrogen fertilizer applications to a seed crop reduced the concentration of mycelia in the seed, with earlier applications having a greater effect. 3) application of the fungicide propiconazole (Tilt) to a seed crop reduced the endophyte concentration in the seed. 4) the endophyte concentration in the seed was found to directly influence the endophyte concentration in seedlings, six month old plants and that of seed harvested from a first year seed crop. As there have been no previous reports of tetraploid perennial ryegrass cultivars with endophyte an experiment was conducted to determine if these could be developed by the standard procedure of colchicine treatment. The results revealed that endophyte was retained following colchicine treatment.

2 pp. / Describes how to select the appropriate lawn mower to properly mow the species of grass at the correct height for high, medium, or low maintenance levels.

The study was designed to assess L. multiflorum subsp. multiflorum, L. multiflorum subsp. italicum and L. x hybridum species and varieties of different ploidy from the agro-biological and breeding viewpoint under Lithuania’s conditions. It has been established that morpho–anatomical assessment and DNA electrophoregram analysis are suitable for the identification of L. multiflorum subsp. multiflorum. It is the first time in Lithuania we have done comparative research on genetic collections of short-lived ryegrass species (L. multiflorum subsp. multiflorum, L. multiflorum subsp. italicum and L. x hybridum) agro-morphological traits, biological characteristics and feeding value. Dry matter yield stability of L. multiflorum subsp. multiflorum varieties has been established in different agro-climatic conditions according to the “genotype x environment” model. Comparison and assessment of L. multiflorum subsp. multiflorum cultivation possibilities in mixtures with legumes (Vicia sativa, Trifolium resupinatum) in conventional and organic production systems have been done. / Tyrimo tikslas buvo įvertinti L. multiflorum subsp. multiflorum, L. multiflorum subsp. italicum ir L. x hybridum rūšis bei skirtingo ploidiškumo veisles agrobiologiniu ir selekciniu požiūriu Lietuvos sąlygomis. Nustatyta, kad anatominė–morfologinė ir DNR elektroforegramų analizės tinka identifikuoti L. multiflorum subsp. multiflorum. Pirmą kartą Lietuvoje atlikti trumpaamžių svidrių rūšių (L. multiflorum subsp. multiflorum, L. multiflorum subsp. italicum ir L. x hybridum) genetinių kolekcijų palyginamieji agromorfologinių požymių, biologinių savybių ir pašarinės vertės tyrimai. Nustatytas L. multiflorum subsp. multiflorum veislių SM derliaus stabilumas skirtingose agroklimatinėse sąlygose pagal modelį „genotipas – aplinka“. Palygintos ir įvertintos L. multiflorum subsp. multiflorum auginimo galimybės mišiniuose su pupiniais augalais tradicinėje ir ekologinėje žemdirbystės sistemose.

A well-managed irrigation scheduling system needs a rapid, preCIse, simple, costeffective and non-destructive soil water content sensor. The PRl profile probe and Diviner 2000 were used to determine the timing and amount of irrigation of three cover crops (Avena sativa L., Secale cereale L. and Lolium multiflonlm Lam.), which were planted at Cedara, KwaZulu-Natal. The PRl profile probe was first calibrated in the field and also compared with the Diviner 2000. For the calibration of the PRl profile probe the factory-supplied parameters (aJ = 8.4 and ao = 1.6) showed good correlation· compared to the soil-estimated parameters (aJ = 11.04 and ao = 1.02). The factorysupplied parameters gave a linear regression coefficient (r2 ) of 0.822 and root mean square error (RMSE) of 0.062. The soil-estimated parameter showed a linear regression coefficient of 0.820 with RMSE of 0.085. The comparison between the soil water content measured using the PR1 profile probe and Diviner 2000 showed a linear regression coefficient of 0.947 to 0.964 with a range of RMSE of 0.070 to 0.109 respectively for the first 100 to 300 mm soil depths. The deeper depths (400, 600 and 1000 mm) showed a linear regression coefficient ofO.716to 0.810 with a range of 0.058 to 0.150 RMSE. These differences between the shallow and deeper depths could be due to soil variability or lack of good contact between the access tube and the surrounding soil. To undertake irrigation scheduling using the PRl profile probe and Diviner 2000, the soil water content limits were determined using field, laboratory and regression equations. The field method was done by measuring simultaneously the soil water content using the PR1 profile probe and soil water potential using a Watermark sensor and tensiometers at three depths (100, 300 and 600 mm) from a 1 m2 bare plot, while the soil dries after being completely saturated. The retentivity function was developed from these measurements and the drained upper limit was estimated to be 0.355 m3 m-3 when the drainage from the pre-wetted surface was negligible. The lower limit was calculated at -1500 kPa and it was estimated to be 0.316 m3m,3. The available soil water content, which is the difference between the upper and lower limit, was equal to 0.039 m3 m,3. In the laboratory the soil water content and matric potential were measured from the undisturbed soil samples taken from the edge of the 1 m2 bare plot before the sensors were installed. Undisturbed soil samples were taken using a core sampler from 100 to 1000 mm soil depth in three replications in 100 mm increments. These undisturbed soil samples were saturated and subjected to different matric potentials between -1 to -1500 kPa. In the laboratory, the pressure was increased after the cores attained equilibrium and weighed before being subjecting to the next matric potential. The retentivity function was then developed from these measurements. The laboratory method moved the drained upper limit to be 0.390 m3 m,3 at -33 kPa and the lower limit be 0.312 m3m-3 at -1500 kPa. The regression equation, which uses the bulk density, clay and silt percentage to calculate the soil water content at a given soil water potential, estimated the drained upper limit to be 0.295 m3m-3at -33 kPa and the lower limit 0.210 m3 m,3 at -1500 kPa. Comparison was made between the three methods using the soil water content measured at the same soil water potential. The fieldmeasured soil water content was not statistically the same with the laboratory and estimated soil water content. This was shown from the paired-t test, where the probability level (P) for the laboratory and estimated methods were 0.011 and 0.0005 respectively at 95 % level of significance. However, it showed a linear regression coefficient of 0.975 with RMSE of 0.064 when the field method was compared with the laboratory method. The field method showed a linear regression coefficient of 0.995 with RMSE of 0.035 when compared with the estimated method. The timing and amount of irrigation was determined using the PR1 profile probe and Diviner 2000. The laboratory measured retentivity function was used to define the fill (0.39 m3 m-3 ) and high refill point (0.34 m3 m-3 ). The soil water content was measured using both sensors two to three times per week starting from May 29 (149 day of year, 2002) 50 days after planting until September 20 (263 day of year) 11 days before harvesting. There were five irrigations and twenty rainfall events. The next date of irrigation was predicted graphically using, the PRl profile probe measurements, to be on 3 September (246 day of year) after the last rainfall event on 29 August (241 day of year) with 8 mm. When the Diviner 2000 was used, it predicted two days after the PRl profile probe predicted date. This difference appeared since the Diviner 2000-measured soil water content at the rooting depth was slightly higher than the PRl profile probe measurements. The amount of irrigation was estimated using two comparable methods (graphic and mathematical method). The amount of irrigation that should have been applied on 20, September (263 day of year) to bring the soil water content to field capacity was estimated to be 4.5 hand 23 mm graphically and 5.23 hand 20 mm mathematically. The difference between these two methods was caused due to the error encountered while plotting the correct line to represent the average variation in soil water content and cumulative irrigation as a function of time. More research is needed to find the cause for the very low soil water content measurements of the PRI profile probe at some depths. The research should be focused on the factors, which could affect the measurement of the PRl profile probe and Diviner 2000 like salinity, temperature, bulk density and electrical conductivity. Further research is also needed to extend the non-linear relationship between the electrical resistance of the sensor and soil water potential up to -200 kPa. This non-linear equation of the Watermark is only applicable within the range of soil water potential between -10 and -100 kPa. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2003.

Lolium perenne L. (perennial ryegrass) generally fails to persist under the sub-tropical cpnditions of South Africa. Furthermore, little research data are available on how to manage this species locally. This study was designed to identify the management options, particularly with r espect to grazing defoliation, which would help enhance the longevity of perennial ryegrass pastures. This was addressed by: 1) reviewing on-farm management practices of perennial ryegrass in KwaZulu-Natal; 2) conducting a detailed two-year field study of the effects of grazing frequency (HF, MF and LF = high, medium and low frequency, respectively) and intensity (HI, MI and LI = high, medium and low intensity, respectively), rotationally applied with the addition of a continuous grazing treatment (CG), on parameters linked to persistency. tiller population dynamics, dry matter These included: (DM) yield and quality, perennial ryegrass vigour, weed invasion and root development; and 3) examining effects of different levels of applied nitrogen (N) during the establishment year on various parameters linked to persistency. These included: tiller population densities, DM yield and quality, perennial ryegrass vigour, weed invasion and root development. The review of on-farm management practices of perennial ryegrass growers in KwaZulu-Natal revealed that reasonably high rates of N application (e.g. 350 and 250 kg N ha¯¹ a¯¹ to perennial ryegrass as pure and clover-based stands, respectively) are important for pasture survival. However, a consistent distribution of the applied N is even more important (i. e. at least seven split applications of N onto pure stands of perennial ryegrass and five onto perennial ryegrass-clover). In terms of grazing management, the period of absence of animals from the pasture during summer was identified as the most important grazing variable affecting pasture survival (i.e. ≥ 21 days). Also, the length of the period of occupation by animals should be as short as possible, particularly during summer (i. e. ≤ 3 days). Paying careful attention to summer irrigation is also an important variable contributing to pasture survival. Grazing intensity was not highlighted as an important contributor to pasture survival. In terms of tillering potential, DM yield and quality (cellulose dry matter disappearance and herbage N) and perennial ryegrass vigour, perennial ryegrass followed definite seasonal trends. These were highest during autumn and spring and were lowest during the mid to late summer period. Perennial ryegrass was most susceptible to general sward degradation through poor management during the mid to late summer period when the danger from weed invasion is greatest and its growth potential, vigour and tillering abilities are lowest within these seasonal periods, grazing defoliation produced marked effects. In terms of tiller survival, DM yield, plant vigour, reduced weed invasion and root production, treatments incorporating low frequency grazing (e.g. LFLI and LFHI) generally out-performed (P≤0.05) those incorporating high frequency grazing, irrespective of the intensity (e.g. HFHI, HFLI, and continuous grazing (CG)). The defoliation treatment incorporating medium frequency and intensity (MFMI) (currently the recommended defoliation strategy for perennial ryegrass) was also out-performed in many instances (P~0.05) by the low frequency treatments (e.g. LFHI and LFLI) . During the establishment year, increasing levels of applied N increased (P≤O. 05) perennial ryegrass DM yields and herbage quality. Models predicting the response of DM yield and quality to applied N suggest linear responses up to 720 kg N ha¯¹ a¯¹. Further refinement of such models and the inclusion of animal production parameters is recommended. Maximum (P≤0.05) tiller population densities occurred at applied N levels of 480 kg ha¯¹ a¯¹. Perennial ryegrass vigour increased (P≤O. 05) with increasing levels of applied N up to 480 kg h¯¹ a¯¹, but individual tiller vigour decreased. Increasing levels of applied N up to 360 kg ha¯¹ a¯¹ suppressed (P≤O. 05) weed tiller densities. Increasing levels of applied N (up to 600 kg h¯¹) increased (P≤O. 05) the root organic matter (OM) per unit volume of soil in the top 5 cm of the soil and decreased root OM per unit volume in the 10 - 20 cm soil depth category. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1994.

Lolium perenne cv. Nui is a cultivar of ryegrass grown throughout New Zealand in pastures due to favourable traits such as high palatability for livestock and its ability to withstand intensive grazing. However, the productivity of pastures is reduced when levels of aluminium and other metals accumulate in soils to toxic levels, a phenomenon referred to as the ‘acid soil syndrome’. In response to this toxicity, plants activate a series of antioxidant reactions, with one catalysed by the superoxide dismutase (SOD) enzymatic system. The enzyme system comprises three isoenzymes, a Cu/ZnSOD, FeSOD and a MnSOD which catalyse the same reaction but differ in amino acid sequence, molecular mass and the metal ion co-factor (hence Cu/ZnSOD, FeSOD and MnSOD). Together these isoenzymes combat the damaging effect of superoxide radicals which accumulate due to metal toxicity. In this thesis, the isolation of genes encoding isoenzymes of the SOD enzyme from L. perenne cv. Nui is described. As well, the growth of L. perenne cv. Nui and changes in expression of the SOD genes encoding each isoenzyme in response to aluminium treatment (0.2mM AlCl3) is investigated. A 1072 bp FeSOD gene sequence and a 705 bp MnSOD gene sequence were isolated from shoot tissue of L. perenne cv. Nui using a combination of RT-PCR with degenerate primers and 3'-RACE. The FeSOD gene comprised 572 bp of the coding sequence and 500 bp of 3'-UTR while the MnSOD gene comprised 508 bp of coding sequence and a 197 bp 3'-UTR. By alignment of each sequence with the gene from the database with highest identity it was predicted that the translation start codon (ATG) is located a further 196 bp upstream for the FeSOD gene (aligned with an Oryza sativa FeSOD sequence as a reference) and a further 152 bp upstream for the MnSOD sequence (aligned with a Triticum aestivum MnSOD sequence as a reference). Using RT-PCR with degenerate primers, a 313 bp CuSOD sequence was predominantly cloned from shoot tissue of L. perenne cv. Nui, but it was not possible to generate the 3'-UTR using 3'-RACE. For growth analysis, seedlings of L. perenne cv. Nui were germinated and acclimatised in Hoagland’s solution, and then subjected to either aluminium treatment (0.2mM AlCl3) or no treatment to act as a control over a designated time course of 0, 4, 8, or 24 hours. Two growth trials were conducted that differed in the age of seedlings used and plant tissues were separated into root and shoot tissues. Similar growth trends were observed in both trials, but the sampling regime in the second growth trial meant that statistical analysis could be carried out. In this trial, analysis revealed that over a time course of 24 hours exposure to 0.2mM aluminium, both root and shoot tissue fresh weight did not significantly differ when compared to the control (no aluminium). A general trend of an increase in root and shoot fresh weight was observed in plants treated with aluminium, but this trend was not significant at P=0.05. No significant change in fresh weight partitioning from shoot to root, or root to shoot in response to aluminium was also observed. Using semi-quantitative Reverse Transcriptase-Polymerase Chain Reaction (sqRTPCR) and primers based around the 3'-UTR with RNA isolated from plants grown in the second hydroponic trial, it was determined that under the conditions used, expression of the FeSOD and MnSOD genes isolated in this study were neither up-regulated or downregulated in response to aluminium treatment in both shoot and root tissue. Further, using degenerate primers to detect expression of one or more genes encoding the Cu/ZnSOD isoenzyme, total expression of the Cu/ZnSOD isoenzyme was also unresponsive to aluminium treatment.

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.

Lolium perenne cv. Nui is a cultivar of ryegrass grown throughout New Zealand in pastures due to favourable traits such as high palatability for livestock and its ability to withstand intensive grazing. However, the productivity of pastures is reduced when levels of aluminium and other metals accumulate in soils to toxic levels, a phenomenon referred to as the ‘acid soil syndrome’. In response to this toxicity, plants activate a series of antioxidant reactions, with one catalysed by the superoxide dismutase (SOD) enzymatic system. The enzyme system comprises three isoenzymes, a Cu/ZnSOD, FeSOD and a MnSOD which catalyse the same reaction but differ in amino acid sequence, molecular mass and the metal ion co-factor (hence Cu/ZnSOD, FeSOD and MnSOD). Together these isoenzymes combat the damaging effect of superoxide radicals which accumulate due to metal toxicity. In this thesis, the isolation of genes encoding isoenzymes of the SOD enzyme from L. perenne cv. Nui is described. As well, the growth of L. perenne cv. Nui and changes in expression of the SOD genes encoding each isoenzyme in response to aluminium treatment (0.2mM AlCl3) is investigated. A 1072 bp FeSOD gene sequence and a 705 bp MnSOD gene sequence were isolated from shoot tissue of L. perenne cv. Nui using a combination of RT-PCR with degenerate primers and 3'-RACE. The FeSOD gene comprised 572 bp of the coding sequence and 500 bp of 3'-UTR while the MnSOD gene comprised 508 bp of coding sequence and a 197 bp 3'-UTR. By alignment of each sequence with the gene from the database with highest identity it was predicted that the translation start codon (ATG) is located a further 196 bp upstream for the FeSOD gene (aligned with an Oryza sativa FeSOD sequence as a reference) and a further 152 bp upstream for the MnSOD sequence (aligned with a Triticum aestivum MnSOD sequence as a reference). Using RT-PCR with degenerate primers, a 313 bp CuSOD sequence was predominantly cloned from shoot tissue of L. perenne cv. Nui, but it was not possible to generate the 3'-UTR using 3'-RACE. For growth analysis, seedlings of L. perenne cv. Nui were germinated and acclimatised in Hoagland’s solution, and then subjected to either aluminium treatment (0.2mM AlCl3) or no treatment to act as a control over a designated time course of 0, 4, 8, or 24 hours. Two growth trials were conducted that differed in the age of seedlings used and plant tissues were separated into root and shoot tissues. Similar growth trends were observed in both trials, but the sampling regime in the second growth trial meant that statistical analysis could be carried out. In this trial, analysis revealed that over a time course of 24 hours exposure to 0.2mM aluminium, both root and shoot tissue fresh weight did not significantly differ when compared to the control (no aluminium). A general trend of an increase in root and shoot fresh weight was observed in plants treated with aluminium, but this trend was not significant at P=0.05. No significant change in fresh weight partitioning from shoot to root, or root to shoot in response to aluminium was also observed. Using semi-quantitative Reverse Transcriptase-Polymerase Chain Reaction (sqRTPCR) and primers based around the 3'-UTR with RNA isolated from plants grown in the second hydroponic trial, it was determined that under the conditions used, expression of the FeSOD and MnSOD genes isolated in this study were neither up-regulated or downregulated in response to aluminium treatment in both shoot and root tissue. Further, using degenerate primers to detect expression of one or more genes encoding the Cu/ZnSOD isoenzyme, total expression of the Cu/ZnSOD isoenzyme was also unresponsive to aluminium treatment.