Stage Development and Flowering in Dactylis glomerata L.

The results of pilot experiments lead to the conclusion thatD. glomerata exhibits a number of developmental stages: firstly,a juvenile stage during which the plant is insensitive to environmentalconditions which later stimulate flowering; secondly, an inductivestage, when the plant responds to periodic exposure to darknessat the conclusion of which it is fully induced or ripe to flower,and finally, a post-inductive stage during which inflorescencesare initiated and undergo further development; these are long-dayprocesses. In four populations studied the juvenile stage lasts about fiveweeks. In north European material daily exposure to seven hoursof darkness is near the minimum for induction although thereis considerable within-population variation. Further, it appearsthat the daily dark requirement becomes less as the plant ages. Comparisons are made of the flowering behaviour of D. glomerataand Lolium perenne. The differences between these species resultfrom the presence of a juvenile stage in Dactylis and the possibilityof satisfying its inductive requirement by long days. Inductionin Lolium requires short days or low temperature. The significance of these results is discussed in the lightof previous work on the environmental control of flowering inherbage grasses. The existence of three developmental stagescan explain the wide differences in interpretation of the floweringrequirements of Dactylis previously held. The possible evolutionof flowering requirements is also discussed.     

The Influence of Seed Size Variation on Seed Germination and Seedling Vigour in Diploid and Tetraploid Dactylis glomerata L.

In this study the effects of seed size variation on germinationand seedling vigour have been investigated within and betweenploidy levels of diploid and related autotetraploid Dactylixglomerata. Rates of seed germination and seedling growth werecompared in two contrasting environments using diploid and tetraploidseeds of equal and also different biomass. Within each ploidylevel, seed biomass had no effect on either the overall percentagenor the rate of germination. In contrast, the comparison ofseeds of equal biomass but differing in ploidy level showedthat seeds from tetraploid plants germinated faster and to ahigher percentage than those from diploid plants. With respectto seedling growth, heavier seeds from the tetraploid genotypesgave seedlings of significantly higher biomass than those fromlighter tetraploid and diploid seeds throughout the 2 monthsof study. Interestingly, seeds of equal biomass but from differentploidy levels produced seedlings more similar than those fromthe extreme seed weight categories. These differences were maintainedin two different environmental conditions. These results suggestthat there is a complex interdependance of seed size and ploidyon seed germination and seedling growth but is not a simpleconsequence of differences in seed size between diploids andtheir related tetraploids.Copyright 1995, 1999 Academic Press Dactylis glomerata, polyploidy, seed size, germination, seedling     

Plantlet formation from cultured inflorescences of Dactylis glomerata L.

The objective of this study was to demonstrate plantlet formation from cultured mature inflorescences of field-grown orchardgrass (Dactylis glomerata L.) plants. Whole tillers were collected and maintained in the dark at 4°C for either 19 or 25 days before panicle sections were plated on a Linsmaier and Skoog (LS) or Schenk and Hildebrandt (SH) agar medium containing 2,4-D. Generally, better results for both cell proliferation and plantlet formation were obtained with 1) large explants (many florets) on 9.1 μM 2,4-D compared to small explants (few florets) on 1.0 μM 2,4-D, 2) SH rather than LS medium and 3) when tillers were pretreated at 4°C for 25 days rather than 19 days. Chromosome counts of basal leaf cells in 94 regenerated plants showed that no plants possessed the gametic chromosome number of n=14.     

鸭茅种质资源多样性研究进展

鸭茅是世界范围内广泛栽培的一种重要禾本科牧草,具有高产、优质、耐荫性强等特性。我国的野生鸭茅资源十分丰富,分布广泛,基因资源优良,但有关鸭茅的研究报导相对较少。为了更好地开发利用这一优良的牧草资源,本从形态学、细胞学和分子水平对国内外鸭茅种质资源多样性的研究进行了综述,并对今后我国的鸭茅研究工作提出了建议。     

Successful crosses between Festuca arundinacea Schreb. and Dactylis glomerata L.

Summary Five F₁ plants have been obtained after extensive crossing between different ecotypes or varieties of Festuca arundinacea Schreb. and Dactylis glomerata L. The success did not appear to depend on specific treatments (spraying with -aminocaproic acid or gibberellic acid or pre-pollination with killed pollen from the seed parent), but the crossability is limited to exceptional plants.F₁ hybrids showed characteristics of both the parents. In four hybrids various developmental disturbances were observed (low viability, aneusomaty, absence of development of inflorescences). Only one hybrid consistently showed 2n=35 chromosomes, good viability and growth, however, it was sterile. After clonal propagation, attempts for polyploidization were started.     

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.     

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.     

Cocksfoot (Dactylis glomerata) Grown for Production of Seed

In grasses grown for production of seed under field conditions,it has been found that only a small proportion of tillers produceinflorescences. For a period of 23 weeks from 4 February 1963a study was made of cocksfoot grown for production of seed inan attempt to discern whether the ability of tillers to becomereproductive was related to specific morphological features.Most tillers which initiated spikelets were rooted, and rootsquickly developed on unrooted tillers which had initiated spikelets.It appeared that larger tillers, judged on the basis of dry-weight,were more likely to become fertile than smaller tillers; importantfeatures of tiller size were the length of the stem and theweight of green leaf (lamina) borne by the tiller. The potentialnumber of inflorescences was reduced considerably by the death,in June, of tillers with completely differentiated apices.     

Polyploidy and habitat differentiation in Dactylis glomerata L. from Galicia (Spain)

Summary The microdistribution of diploid and tetraploid plants of Dactylis glomerata L. was examined and related to their immediate environment in several sites in central Galicia, where morphologically indistinguishable individuals of both ploidies grow in sympatry. The two related cytotypes differed in habitat preference. Diploids were mainly confined to the low-density forest-floor habitat in woodlands of mostly ancient origin, whereas tetraploids were widespread in varied habitats but clearly predominant in open areas, particularly in disturbed anthropic sites. The in situ comparison of plant performance showed that where plants of each ploidy were more common they produced more tillers, panicles and seeds. This habitat preference closely reflected differences in life-history characteristics. The tetraploids had an early and short flowering time almost always completed before the aestival drought, whereas the diploids began to flower several weeks later and flowered throughout the drought. Comparisons along artificial gradients of soil water availability and light transmittance indicated that the cytotypes had distinct physiological requirements which probably originated in metabolic and more general genetic differentiation and could be directly attributable to ploidy. Habitat differentiation increases the species' colonizing ability. It also amplifies divergence in reproductive strategy between diploids and tetraploids, which reduces ineffective crossing between cytotypes and thereby permits them to coexist in sympatry. The effect of hybridization at the polyploid level on the differentiation between cytotypes was assessed from the recent introduction of a foreign tetraploid entity into the study area. Hybridization between the two distinct tetraploids was found to increase habitat differentiation between the diploids and the tetraploids, but the major part of this differentiation is probably attributable to ploidy itself.     

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     

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.     

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.     

Time Changes of Relative Growth-rate in two Natural Populations of Dactylis glomerata L.

Changes in the relative growth-rate (RGR) between successiveharvests were studied in two natural populations of Dactylisglomerata, one from Norway and the other from Portugal, grownat four temperatures in a 16-h photoperiod. Young seedlingswere harvested at six equal intervals of 7 days at 5 and 10°C and 3.5 days at 20 and 30 °C. Quadratic curves werefitted to log_e dry weight by a method employing inverse matrices.There was a decline in RGR with time and the magnitude of thisdecline differed for the two populations with an intersectionof the curves at each temperature. At 5 and 10 °C the RGRof the Portuguese population was greater than that of the Norwegianat the initial harvests, but it declined more rapidly than theRGR of the Norwegian population. This relationship was reversedat 20 and 30 °C, with the RGR of the Norwegian populationbeing greater when the plants were small, and declining morerapidly with time. The implications of these changes in RGRare discussed in relation to earlier growth-analysis experimentswhere only two harvests were taken.     

野生鸭茅种质遗传多样性的AFLP分析

本文应用扩增片段长度多态性（AFLP）技术,从64个引物对中筛选出9个,分别对37份鸭茅种质进行扩增,共得到400条清晰条带。其中多态性带336条,平均多态位点水平为84.0%,表现出较高的多态性。利用NTSYS-pc软件计算种质间的遗传距离,变化范围为0.0692～0.4214。用UPGMA方法进行聚类分析,在遗传相似系数为0.81水平上37份鸭茅种质可分为8个类群。用EIGEN方法进行主坐标分析,建立种质间相互关系的二维图。各种质在二维图中的分布与UPGMA聚类基本吻合。从分子水平分析,鸭茅遗传变异与染色体倍性和地理分布密切相关。