Skew distribution of panicle-emergence dates in populations of cock's-foot, Dactylis glomerata L. (Gramineae)

The date distribution of emergence in panicles of Dactylis glomerata was studied over several years at the Welsh Plant Breeding Station, Aberystwyth. Indigenous populations from southwest England, and western France showed a negatively skew distribution, as did cultivars from U.S.A., Denmark, and New Zealand, but in those from U.S.S.R. the skewness was not significant. It is suggested that this negative skewness could have arisen as a selective response to light intensity. This could explain why the predominant growth forms in the species' natural habitat are of the taller 'hay' type. The method of growing seed commercially in drilled rows over many generations has eliminated the prostrate forms. The latter have survived in old pastures but never predominate, and may be greatly reduced should the intensity of grazing be increased and prolonged. Self regeneration by 'own' seed in sward plants is hindered by 'Choke' disease (Epichloe typhina) which inhibits and can prevent panicle emergence so that in extreme cases plants become vegetative and non-sexual.
There seems to be no inherent physiological barrier to late heading, but it has not, so far, been possible to assemble a population of agronomically suitable late-flowering plants. For this reason breeders have not been able to produce cultivars of cock's-foot comparable with the late-heading, leafy, grazing varieties developed in Lolium perenne.     

Embryogenic and callus-specific proteins in somatic embryogenesis of the grass,Dactylis glomerata L.

Somatic embryogenesis occurs spontaneously in some monocotyledoneous callus and cell suspension cultures maintained in suitable culture conditions. Nevertherless, the processes involved in somatic embryo development, and factors inducing this differentiation, are poorly understood. In order to study the changes in protein composition accompanying embryogenesis in cell suspension cultures of Dactylis glomerata L., embryos of various sizes and “undifferentiated” callus cells were separated and their total cellular protein extracts analyzed by two-dimensional polyacrylamide gel electrophoresis. Several proteins could be identified that are specific for embryos or callus under various culture conditions. Three independent detection methods were employed: silver-staining of proteins, in vivo labeling of proteins with [³⁵S]methionine, and in vitro translation of poly(A)⁺ RNA. All culture conditions tested, including those that induce embryonic proteins in carrot, fail to induce embryonic proteins in D. glomerata callus cells.     

Initiation of Procambial Strands in Axillary Buds of Dactylis glomerata L., Secale cereale L., and Lolium perenne L.

In axillary buds of Dactylis glomerata L., Secale cereale L.,and Lolium perenne L., the first two procambial strands of theprophyll and the median strand of the first normal leaf areinitiated in the bud in isolation from the vascular system ofthe parent axis. They rapidly form connections with the vascularsystem of the parent axis, presumably by downward extension,as is the case of the strands of leaf primordia on the mainaxis.     

The Effect of Sulphur Dioxide on the Growth of Lolium perenne L., Lolium multiflorum Lam., Dactylis glomerata L., and Phleum pratense L.

Lockyer, D. R. 1985. The effect of sulphur dioxide on the growthof Lolium perenne L., Lolium multiflorum Lam., Dactylis glomerataL., and Phleum pratense L.?J. exp. Bot. 36: 1851-1859. Fouragriculturally important grasses, Lolium perenne L., Loliummultiflorum Lam., Dactylis glomerata L. and Phleum pratenseL. were exposed to sulphur dioxide (SO₂) in a system of exposurechambers. The plants were exposed for a total of 43 d to meanconcentrations of SO₂ in the air of 0,87 or 448 (µg m^–3and herbage was harvested twice. All four grasses showed chloroticlesions after exposure to the highest concentration of SO₂.The effect of SO₂ on the yield of herbage was statisticallysignificant only at the second harvest and at the highest concentration;the dry weights of shoots of D. glomerata and L. perenne werereduced by 33% and 16% respectively. Significant effects ofSO₂ were also found on the 'transpiration coefficients' measuredfor D. glomerata and P. pratense. The grasses differed in theiruptake of sulphur from the atmosphere but this was not relatedto their sensitivity to SO₂. Total–S concentration inthe shoots of L. perenne, L. multiflorum and D. glomerata increasedalmost linearly in response to increasing SO₂ concentration;with P. pratense only the highest SO₂ concentration raised total-Sabove the level in control plants. These increases were almostentirely due to the accumulation of sulphate–S. Key words: Sulphur diozide, Lolium perenne, Lolium multiflorum, Dactylis glomerata, Phleum pratense     

Water Use Characteristics of Dactylis glomerata L., Lolium perenne L. and L. multiflorum Lam. Plants

Cocksfoot (Dactylis glomerata L.). perennial ryegrass (Loliumperenne L.) and Italian ryegrass (L. multiflorum Lam.) plantswere grown on deep (75–95 cm) columns of soil in glasshousesand growth rooms with and without irrigation. The species inwhich growth declined least rapidly after water had been withheldwere those which transpired most slowly. During early establishmentin the glasshouse cocksfoot transpired least because of slowroot growth. In the growth room, when root systems were deeperand denser, perennial ryegrass transpired least because of lowleaf water conductance. Results are discussed in relation to(a) drought resistance in the three species; (b) breeding forincreased drought resistance through modifying root distributionand leaf water conductance; and (c) the use of isolated soilcolumns in water relations studies. Dactylis glomerata L., Lolium perenne L., Lolium multiflorum Lam., cocksfoot, perennial ryegrass, Italian ryegrass, transpiration, roots, leaf water conductance     

Phosphorus effect on the uptake,translocation and accumulation of the14C-urea in orchard grass (Dactylis glomerata L.)

Summary The effect of different phosphorus supplies on the uptake, translocation and accumulation of¹⁴C-urea by orchard grass was investigated. Phosphorus starvation inhibits the uptake, translocation and accumulation of the carbon of urea similarly to the nitrogen of urea. As compared with the uptake process the reduction of the accumulation is much more effected by the inhibition of the carbon translocation from roots to the aboveground parts. Lack of phosphorus also decreases the incorporation of the¹⁴C of urea into high-molecular compounds. The effect of phosphorus deficit on the accumulation of¹⁴C-urea increases with time of starvation.     

Evaluation of cocksfoot (Dactylis glomerata L.) population for drought survival and behavior

Climate change models predict frequent and intense droughts in the world. Development of drought-tolerant species and cultivars is necessary to cope with such changes. Forage grass species are affected, especially in the Mediterranean region. The aim of the present study was to investigate the diversity for drought survival, summer dormancy, and productivity within a cocksfoot population.The study was conducted in Morocco, under field conditions from 2011 to 2013. 283 genotypes of cocksfoot and parents were tested, characterized for dry matter yield, heading date, plant height, senescence, summer dormancy, and drought survival. Results exhibited a large variability between traits. 79% of the population had survived after severe drought summer while 57% yielded more than both parents. Also, 63% of the progeny had an intermediate score of summer dormancy estimated by senescence score. Large variability was also noticed for heading date and plant height. Several accessions combined a high yield and persistence under severe summer drought. Which explain the significant correlation (r = 0.18, P < 0.005) founded between total dry matter accumulated in 2013 and plant survival. Accordingly, our results showed that we can rise persistent and resilient genotypes among population with a good level of biomass.     

Phenotypic variation and performance of diploid subspecies of Dactylis glomerata L.

Dactylis glomerata L. is one of the best known examples of a polyploid complex that includes diploid (2n = 14), tetraploid (2n = 28) and hexaploid (2n = 42) types. The diploids, descending from the ancestors of the genus, are numerous, distinct forms adapted to specific environments and include all the morphological variation and ecological adaptation found in Dactylis. The objective of the present study was to shed more light on the differentiation of diploids and to obtain information for better exploiting the genetic resources of this species. To this end we carried out a discriminant analysis in the most widespread diploid subspecies based on a large number of morpho-physiological traits. We found that some characteristics, such as time to heading, time to flowering, vegetative regrowth, plant height and seed shattering are the most discriminant and enabled us to realize a more exact differentiation of the diploids with respect to the morphological criterion generally adopted. The results demonstrated that diploid taxa offer an interesting combination of relevant agronomical and ecological characteristics which could be useful in breeding programs to promote the use of this species in sustainable agriculture systems. We also performed cytological investigations and defined a general karyotype representative of the diploid Dactylis considered in this study.     

Embryoid and plantlet formation from leaf segments of Dactylis glomerata L.

Summary The purpose of this investigation was to demonstrate callus induction and plantlet formation from cultured leaf segments of 12–15 week-old Dactylis glomerata L. (orchardgrass) plants. Flat half-leaf sections, approximately 2–3 mm square, from the three innermost (youngest) leaves were isolated and individually plated serially beginning at the leaf base on a solid SH medium containing 30 M of 3,6-dichloro-oanisic acid (dicamba). Callus formed on leaf sections from all 50 plants used in the study. After transfer to SH medium with 1 M dicamba, plantlets formed from leaf sections of 9 of the 50 plants. In most cases plantlets formed from embryogenic callus but in a few cases embryoids formed directly on the leaf surface without an intervening callus state. These developed into plantlets when transferred to low auxin medium. The response for both callus and plantlet formation decreased with increasing distance both spatially and temporally from the shoot apex. Histological examination of embryogenic callus revealed the presence of non-zygotic embryos in various stages of development. The results provide further support for compentency (if not totipotency) of Gramineae leaf cells.     

Respiratory costs and rate of protein turnover in the roots of a fast-growing (Dactylis glomerata L.) and a slow-growing (Festuca ovina L.) grass species

Protein turnover is generally regarded as one of the most important maintenance processes in plants in terms of energy requirements. In this study, the contribution of protein turnover to the respiratory costs for maintenance in the roots of two grass species, the fast-growing D. actylis glomerata L. and the slow-growing F. estuca ovina L., is evaluated. Plants were grown under controlled-environment conditions in a nutrient solution to which NO(3)- was added at a relative addition rate of 0.2 and 0.1 mol N mol(-1) N already present in the plant d(-1) for D. glomerata and F. ovina, respectively, so as to obtain a steady exponential growth rate close to the plants' maximum relative growth rate. Pulse-chase labelling with (14)C-leucine was used to determine the rate of protein turnover in the grass roots. The rate of turnover of the total protein pool did not differ significantly between the two species. The protein degradation constant in D. glomerata and F. ovina was 0.156 and 0.116 g protein g(-1) protein d(-1), respectively, which corresponds with a total protein half-life of 4 d and 6 d. Assuming specific respiratory costs for protein turnover of 148 mmol ATP g(-1) protein, the estimated respiratory costs for protein turnover in the roots were 2.8 and 2.4 mmol ATP g(-1) root DM d(-1) in D. glomerata and F. ovina, respectively. Both the fast- and the slow-growing grass spent between 22-30% of their daily ATP production for maintenance on protein turnover, which corresponds to 11-15% of the total root ATP production per day. Note that the data presented in this abstract are based on the assumption that 50% recycling of the (14)C-labelled leucine took place in the roots of both grass species.     

Secretion of a chitinase-like protein in embryogenic suspension cultures of Dactylis glomerata L.

A chitinase-like 32 kDa acidic protein with a potential chitinase activity has been identified in the medium of embryogenic suspension cultures of Dactylis glomerata L. using an antiserum raised against endochitinase EP3 from Daucus carota L. The presence of this protein discriminates between Dactylis glomerata L. embryogenic and nonembryogenic suspension cultures and thus could be possibly used as a marker for embryogenic potential.     

The Effect of Temperature on the Growth of Cocksfoot (Dactylis glomerata L.)

The growth of cocksfoot at 14°, 22°, and 26° C wasmeasured at weekly intervals over a period of six weeks. Initially,the relative growth rates increased with increase in temperature,but during the final three weeks they were little differentat all three temperatures. The reduction in relative growthrates with time at 22° and 26° were associated withincreases in size which were partly reflected by reductionsin the leaf-area ratios. It is also likely that at 26° changesin the photosynthetic capacity of leaves, perhaps associatedwith decreasing concentrations of mineral nutrients, contributedto the decreased relative growth rates. Leaf expansion and increase in cell numbers were estimated overtwo-day periods at temperatures ranging from 5° to 30°C. Leaf expansion increased with increase in temperature throughoutthis range; extrapolation suggested that it would cease at temperaturesbelow 3° C. The optimum temperature for cell division appearedto be between 20° and 25°C. Different physiological processes appeared to be involved inthe temperature responses of plants of different sizes and histories.With young plants these responses resulted in a large overalleffect of temperature on the growth rate; with older plantsof the same size there appeared to be several compensatory responsesso that variation in temperature over an apprecaible range hadlittle overall effect.     

Extraction, structural characterisation and evaluation of hydroxycinnamate esters of orchard grass (Dactylis glomerata) as substrates for polyphenol oxidase

Polyphenol oxidase (PPO) activity has been reported in orchard grass (Dactylis glomerata); however, to date, no endogenous substrates have been identified. In the present study, we report the isolation and structural elucidation of PPO substrates in this species. The free phenol fraction was extracted, separated by reverse-phase chromatography and six potential substrates, including two hydroxycinnamate esters, were identified by UV spectrometry, electrospray ionisation-tandem mass spectrometry (LC-ESI-MSⁿ) and 1D and 2D NMR analyses (¹H NMR, ¹³C NMR, DEPT, COSY, HMQC and HMBC). Furthermore, three caffeoylquinic acids (3-CQA, 4-CQA and 5-CQA) were identified by comparison of their spectral data (ESI-MS) with those of known compounds and literature data. Five of these compounds were demonstrated to be substrates for orchard grass PPO.     

Photoperiodic control of flowering in Dactylis glomerata, a true short-long-day plant

Flowering requirements of three Scandinavian cultivars of Dactylis glomerata L. have been studied in controlled environments. At temperatures ranging from 9 to 21°C optimal flowering required 10 weeks of exposure to short days (SD) followed by exposure to long days (LD). Only a few plants flowered in continuous LD and no primary induction took place in any daylength at 24 or 27°C. However, at a temperature of 3°C primary induction occurred also in 24 h LD, but more than 20 weeks of treatment were required for 100% flowering. The critical photoperiod for secondary induction was about 12–13 h, depending on the latitude of origin of the cultivar. A critical number of 12 to 16 LD cycles was required for 100% flowering, although some plants flowered after only 4 LD. A high proportion of viviparous proliferation resulted from marginal LD induction. Initiation of floral primordia did not take place in SD but required a transition from SD to LD. These results demonstrate that D. glomerata is a true short-long-day plant.     

Growth, proline accumulation and water relations of NaCl-selected and non-selected callus lines of Dactylis glomerata L

Sodium chloride-tolerant calli were selected from leaf-derived embryogenic calli of Dactylis glomerata L. on agar solidified medium supplemented with 200 mM NaCl, a concentration lethal to non-selected calli. Growth characteristics, water relations and proline accumulation pattern were compared in selected and non-selected lines. The objective was to gain an understanding of the mechanism(s) of tolerance in the NaCl-tolerant line. Growth in the selected line, as expressed in terms of tolerance index (ratio of fresh wt. on NaCl medium:fresh wt. on NaCl free medium x 100), was greater than that of the non-selected line at all levels of NaCl between 50 and 300 mM. There was no significant difference in proline accumulation in the selected and non-selected lines. Maintenance of turgor by osmotic adjustment was observed in the non-selected line despite decreased growth. In contrast, the selected line lost either the need or the ability to adjust osmotically. There was little or no increase in symplastic osmolality in the selected line when exposed to NaCl. Presumably, selection was made for a salt-excluding tissue that has lost the ability to accumulate solutes and adjust turgor with NaCl stress.     

Geographical distribution and phenotypic differentiation in populations of Dactylis glomerata L. in Japan

Although the perennial grass Dactylis glomerata L. has established dominant populations in Japan since its introduction in the 1870s, there have been marked reductions in its abundance in southern and northeastern regions. In order to examine the effects of climatic factors on distribution and differentiation of the naturalized populations of D. glomerata, abundance of 26 populations over a distance of 1500 km along a latitudinal gradient was recorded at each site, and life-history traits of each population were measured in a common garden. It was found that the reduction in abundance was related to the mean summer temperature in southern regions and to the lowest temperature before snow cover in northeastern regions. Recent climatic records in Japan show an increase in the mean summer temperature but no apparent changes in the lowest temperature before snow cover. These data suggest that, assuming the recent trend in climatic changes continues, the population abundance will decrease in southern regions and will change little in the northeastern regions. Germination speed, leaf width and reproductive allocations showed clinal variation over a geographical range, and the southern populations had more rapid germination, narrower leaves and lower reproductive allocation than did the northern populations. On the other hand, seed size and germination date showed margin-center differentiation. Marginal populations in both distributional borders had smaller seeds and lower germination rates than did the central populations. This revised version was published online in June 2006 with corrections to the Cover Date.