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Perennial ryegrass (Lolium perenne L.) is an important turfgrass and gramineous forage widely grown in temperate regions around the world. However, its perennial nature leads to the inevitable exposure of perennial ryegrass to various environmental stresses on a seasonal basis and from year to year. Like other plants, perennial ryegrass has evolved sophisticated mechanisms to make appropriate adjustments in growth and development in order to adapt to the stress environment at both the physiological and molecular levels. A thorough understanding of the mechanisms of perennial ryegrass response to abiotic stresses is crucial for obtaining superior stress-tolerant varieties through molecular breeding. Over the past decades, studies of perennial ryegrass at the molecular and genetic levels have revealed a lot of useful information to understand the mechanisms of perennial ryegrass adaptation to an adverse environment. Unfortunately, molecular mechanisms by which perennial ryegrass adapts to abiotic stresses have not been reviewed thus far. In this review, we summarize the recent works on the genetic and molecular mechanisms of perennial ryegrass response to the major abiotic stresses (i.e., drought, salinity, and extreme temperatures) and discuss new directions for future studies. Such knowledge will provide valuable information for molecular breeding in perennial ryegrass to improve stress resistance and promote the sustainability of agriculture and the environment. [ABSTRACT FROM AUTHOR]

For pastures, root turnover can have an important influence on nutrient and carbon cycling, and plant performance. Turnover was calculated from mini-rhizotron observations for chicory ( Cichorium intybus), lucerne ( Medicago sativa), perennial ryegrass ( Lolium perenne) and white clover ( Trifolium repens) grown in the Manawatu, New Zealand. The species were combined factorially with four earthworm species treatments and a no-earthworm control. Split plots compared the effects of not cutting and cutting the shoots at intervals. Observations were made c. 18 days apart for 2.5 years. This article concentrates on differences between plant species in root turnover in the whole soil profile to 40 cm depth. At this scale, earthworm effects were generally small and short lived. For ryegrass and white clover, root length and mass were linearly related ( R2 = 0.82-0.99). For chicory and lucerne, the relationships were poorer ( R2 = 0.38-0.77), so for those species length turnover may be a poor indicator of mass turnover. Standing root length, total growth and death generally decreased in the sequence ryegrass > lucerne > chicory = white clover. In length terms, scaled turnover (growth divided by average standing root length) generally followed the sequence lucerne > white clover > perennial ryegrass = chicory. Across species the scaled turnover rate averaged 3.4 per year or 0.9% per day. Cutting shoots reduced standing root length, growth and death, but increased scaled turnover. These results indicate fast and prolonged root turnover. For ryegrass and white clover, at least there is need to reappraise how to measure and model shoot : root ratios, dry matter production and carbon cycling. [ABSTRACT FROM AUTHOR]

Limited information is available on frequency and seasonal timing of irrigation in perennial ryegrass seed crops. Two field experiments were conducted in Oregon to investigate irrigation effects on seed production in seven cultivars of perennial ryegrass. Three spring irrigation treatments were tested in Experiment 1 over a two-year period: none (control), single irrigation to fill the soil profile to field capacity (FC) at anthesis, and multiple irrigations to maintain soil water deficit ≤50 mm below FC until the beginning of seed fill; and single fall and spring irrigation timings were tested in Experiment 2 over a three-year period. Spring irrigation increased seed yield of perennial ryegrass in both experiments while fall irrigation had no effect in the second experiment. A single spring irrigation increased seed yield by an average 16.1% whereas multiple irrigations resulted in an average increased yield of 24.6% in Experiment 1. Single spring irrigation in Experiment 2 increased seed yield by an average 6.5%. Seed yield increases attributable to spring irrigation were the result of a combination of increased seed number and seed weight. Spring irrigation increased harvest index and seed set. Water use efficiency was reduced by spring and fall irrigation. Perennial ryegrass seed crops can benefit from spring irrigation but the frequency of irrigation is best determined by the quantity of water available and economic considerations. [ABSTRACT FROM AUTHOR]

A hydroponics experiment was conducted to test the effects of sodium nitroprusside (SNP, a donor of NO) supplied with different concentrations on copper (Cu) toxicity in ryegrass seedlings (Lolium perenne L.). Excess Cu (200 µM) reduced chlorophyll content, resulting a decrease in photosynthesis. Cu stress induced the production of hydrogen peroxide (H2O2) and superoxide anion (O2...), leading to malondialdehyde (MDA) accumulation. Furthermore, activities of antioxidant enzymes in Cu-treated seedlings such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were decreased. In addition, Cu stress inhibited the uptake of K, Mg, Fe, and Zn and increased Ca content in roots. Moreover, in leaves of Cu-stressed seedlings, K, Fe, and Zn contents were decreased and the contents of Ca and Mg were not affected significantly. In Cu-treated seedlings, Cu concentration in roots was higher than in leaves. Addition of 50, 100, 200 µM SNP in Cu-mediated solutions increased chlorophyll content and photosynthesis, improved antioxidant enzyme activities, reduced Cu-induced oxidative damages, kept intracellular ion equilibrium under Cu stress, increased Cu concentration in roots and inhibited Cu accumulation in leaves. In particular, addition of 100 µM SNP had the best effect on promoting growth of ryegrass seedlings under Cu stress. However, the application of 400 µM SNP had no obvious alleviating effect on Cu toxicity in ryegrass seedlings. [ABSTRACT FROM AUTHOR]

Accurate, rapid, and nondestructive estimates of turfgrass leaf water status are important for site-specific irrigation and drought stress management. The objective of this study was to identify changes and correlations among the canopy reflectance, canopy temperature, and leaf relative water content (RWC) of perennial ryegrass (Lolium perenne L.) under water deficit conditions. Six cultivars of perennial ryegrass were subjected to dry-downs in the field from May to Aug. 2007 and from June to Aug. 2008. Turf quality was positively correlated with soil moisture (SM), RWC, and normalized difference vegetation index (NDVI), but negatively correlated with canopy and ambient temperature differentials (ΔT). ΔT was well correlated with RWC (r = -0.77 to -0.78) and SM (r = -0.66 to -0.74), whereas SM was correlated with RWC (r = 0.64 to 0.74) across seasons in both years. When a wide range of stress symptoms occurred in July and Aug., RWCs became highly correlated with AT (r = -0.80 to -0.89) and NDVI (r = 0.77 to 0.81), whereas AT was correlated with NDVI (r =-0.70 to -0.80) in both years. SM was well correlated with RWC (r = 0.71 to 0.80), NDVI (r = 0.70 to 0.73), and AT (r = -0.76 to -0.78) in July and August in both years. These results suggest that changes in AT can be used to predict well the leaf water and soil moisture content of perennial ryegrass under water deficit conditions. Combined with NDVI, the correlations can be used for direct mapping of the variability in grass water status, thus improving irrigation management. [ABSTRACT FROM AUTHOR]

Perennial ryegrass ( Lolium perenne L.) is the most important grass species for temperate grassland agriculture. The level and distribution of genetic variation in gene bank ecotype collections is still largely unknown but of great interest for the planning of breeding programs. The objectives of this study were to (i) assess the molecular diversity of Polish ecotypes of perennial ryegrass, and (ii) compare the relationship between this group and German ecotypes and European cultivars investigated previously. A total number of 166 polymorphic marker bands were detected among the 171 individual plants of the 9 Polish ecotypes. In a joint analysis with 9 Polish and 22 German ecotypes, and 22 European cultivars 172 polymorphic RAPD markers could be found. Genetic distance among the Polish ecotypes ranged from 0.31 to 0.51, while for all 53 populations a broader range was detected (0.25–0.67). An analysis of molecular variance (AMOVA) revealed a much larger variation within populations (71%) than among them (29%). The Polish ecotypes contained the highest within population variation (74%). The largest among group difference (15%) was found between the Polish ecotypes versus all other accessions. We conclude that the Polish ecotypes represent a valuable genetic resource for enlarging the genetic variation in the West European germplasm pool of perennial ryegrass. [ABSTRACT FROM AUTHOR]

Background: Pyrrolizidine alkaloids (PAs) are a class of secondary metabolites that function as feeding deterrents in a range of different plant species. In perennial ryegrass (Lolium perenne L.) the only PAs that have been identified are the thesinine-rhamnoside group, which displays significant genetic variation. Homospermidine synthase (HSS) has evolved from deoxyhypusine synthase (DHS) and catalyses the first step in the PA pathway, making it a key candidate for the investigation of genes influencing observed PA trait variation. Results: During PCR amplification and sequence analysis of DHS we identified two putative HSS genes in perennial ryegrass. One of the genes (LpHSS1) was absent in some perennial ryegrass plants. Thesinine-rhamnoside levels were measured using liquid chromatography coupled with mass spectrometry in a diverse association mapping population, consisting of 693 plants free of fungal endophytic symbionts. Association tests that accounted for population structure identified a significant association of absence of the LpHSS1 gene with lower levels of thesinine-rhamnoside PAs. HSS-like gene sequences were identified for other grass species of the Poaceae, including tall fescue, wheat, maize and sorghum. Conclusion: HSS is situated at the crucial first step in the PA pathway making it an important candidate gene for investigation of involvement in PA phenotypic variation. In this study, PA level in perennial ryegrass was strongly associated with the presence or absence of the LpHSS1 gene. A genetic marker, developed for the presence/absence of LpHSS1, may be used for marker-assisted breeding to either lower or increase PAs in breeding populations of perennial or Italian ryegrass to investigate a potential role in the deterrence of herbivore pests. The presence of HSS-like genes in several other Poaceae species suggests that PA biosynthesis may occur in plant family members beyond perennial ryegrass and tall fescue and identifies a potential route for manipulating PA levels. [ABSTRACT FROM AUTHOR]