Genetic control of androgenetic response in Lolium perenne L.

In a study of androgenesis in 90 Norwegian genotypes of perennial ryegrass (Lolium perenne L.), heritabilities ranged from h _b ² =0.46 to 0.80. Very high or completely positive genotypic correlations were found between most characters of androgenetic response (e.g. embryo-like structures per 100 anthers, plants per 100 embryo-like structures, albino plants per 100 anthers, green plants per 100 anthers). Three genotypes, 2 Norwegian (7-5 and 9-5) and 1 Danish (245), which had significantly different androgenetic responses were selected to study the genetic control of the processes. Genotypes 7-5 and 9-5 were highly embryogenie, 7–5 and 245 were relatively high producers of green plants, while 9-5 was unable to produce green plants. The six possible reciprocal crosses between these three genotypes were made, and 10 or 11 F₁ plants from each cross were used for anther culture experiments. The cross 7-5 x 245 showed average superiority over both parents for total plant regeneration and green plant production, results not previously reported. The phenotypic correlations estimated among progenies from the crosses ranged from r=-0.99^*** to 0.81^***. These considerable changes, relative to the results of the screening experiment, are most likely the result of changed allele frequencies caused by the strong selection of parents in these crosses, and a relatively simple genetical control. This is also inferred from the large transgressive segregation observed.Abbreviations ANT anthers - ELS embryo-like structures - ALB albino plants - GRP green plants - DH doubled haploid plants     

Efficacy of Selective Gametocides on Lolium perenne L.

The efficacy of six chemicals as selective male gametocideson perennial ryegrass plants was studied by making use of agenetic marker technique. In a preliminary screening experimenteach of the chemicals was used in five concentrations and infive treatments at several stages of development at or nearear emergence. Promising treatments from within this experimentwere assessed in more detail subsequently. In most treatmentsfemale fertility was impaired more than male fertility. In thetreatments in which the desired effect was found, i.e. malefertility was depressed appreciably more than female fertility,the differential gametocidal selectivity of the chemicals couldnot be considered distinct enough to merit application on afield scale.     

The genetic control of incompatibility in Lolium perenne L.

An examination of the incompatibility mechanism of Lolium perenne using the pollen stigma reaction has revealed that no precise one or two locus system is operative in this species.     

黑麦草内生真菌感染状况的检测及定量分析

选取内生真菌特异性引物,成功建立了利用PCR技术对黑麦草中内生真菌感染状况的检测和定量分析方法。此检测方法的准确性高于常规乳酸-苯胺蓝染色法。利用实时荧光PCR定量分析的结果表明：不同植株之间内生真菌含量差异较大,而同株植物相同龄级分蘖之间内生真菌含量无显著差异。由此可见内生真菌的含量不仅与植物种以及品种有关,也与植物的基因型密切相关。     

The Growth and Survival of Severely-shaded Tillers in Lolium perenne L.

The effect of shading a single tiller to below its compensationpoint for a period of 5 weeks in vegetative plants of Loliumperenne L. cv. S23, was studied in two different experimentseach employing two light regimes, one of which was common toboth experiments. In the first experiment tillers in the axils of the first leafwere shaded three weeks from appearance at both 40 and 70 Wm^–2. None of the shaded tillers died and they continuedto produce new leaves and increase in dry weight but at a reducedrate. In the second experiment, tillers with one emerged leafin any leaf axil position were shaded at 70 W m^–2 andin a treatment in which light was reduced to 13 W m^–2after initial growth at 70 W m^–2. As in the first experimentall shaded tillers survived at 70 W m^–2 but in the 70 13 W m^–2 transfer regime all shaded tillers died. In the second experiment shaded tillers in both light regimeswere supplied with ¹⁴C-assimilate by translocation from theremainder of the plant but in the 70 13 W m^–2 the initialsupport was withdrawn within 5 weeks of shading. The results are discussed in terms of the physiological relationshipsbetween the tillers of the grass plant. Lolium perenne L., growth of tillers, survival of tillers, effect of light     

黑麦草(Lolium perenne L.)内生真菌的检测、分离及鉴定

从多年生黑麦草(LoliumperenneL.)5个品种———SR4000、Pinnacle、Topgun、CalypsoⅡ、Justus中分离出61个菌株。次培养后,所得形态稳定的菌株可分为4个形态群,依据其形态特征及APPCR的结果,确定其中的57个分离菌株为Neotyphodiumlolii。     

Chromosome pairing in tetraploid hybrids between Lolium perenne and L. multiflorum

Summary Chromosome association at first meiotic metaphase in tetraploid hybrids between Lolium perenne and L. multiflorum was compared with that in autotetraploid L. perenne. The hybrids were found to have significantly higher levels of bivalent frequency, and lower levels of multivalent and chiasma frequency. A significant increase in multivalent frequency with increasing chiasma formation was found in both groups, but the increase was much less in the hybrids. These differences in chromosome associations between the two groups must therefore reflect differences in chiasma distribution and it is suggested that the results indicate a significant degree of preferential bivalent pairing in the hybrids.     

The typification of Lolium perenne L. and Loliutn temulentum L. (Poaceae)

LOOS, B. P. & JARVIS, C. E., 1992. The typification of Lolium perenne and Lolium temulentum (Poaceae). The typification of the Linnaean species Lolium perenne and Lolium temulentum has been studied. Lolium perenne is typified by material in LINN, as proposed by Terrell, but it has been necessary to select a lectotype for L. temulentum , and material in the Burser herbarium (UPS) has been chosen for this purpose. The study shows that although Linnaeus used awns as a diagnostic character to distinguish the two species, he was aware of the intraspecific variability in this character.     

Field performance of cell-suspension-derived Lolium perenne L. regenerants and their progenies

 Two sets of plants (Lb and Lc), regenerated from different single-genotype-derived embryogenic suspension cultures of Lolium perenne cv Citadel, were evaluated for agronomic traits in a modified polycross design in the field. Seed from the primary regenerated plants was harvested to evaluate morphological and phenological traits of corresponding progenies in a replicated field experiment. When compared to seed-grown plants of the same cultivar, primary regenerants of the Lb set showed a significant delay in ear emergence and a more-erect growth habit, while primary regenerants from the Lc set showed a significantly higher seed yield. However, progenies of regenerated plants did not differ from those of seed-grown plants. Embryogenic suspension cells of L. perenne have the potential for producing fertile, well-performing, material which can be integrated into breeding programs. Received: 3 November 1997 / Accepted: 25 November 1997     

The Pattern of Abortion of Developing Seeds in Lolium perenne L.

The pattern of seed abortion was followed in each floret offour centrally positioned spikelets in inflorescences of L.perenne from field plots given zero ( –F) or 150 kg Nh^–1 ( + F). There was severe lodging prior to anthesisin the +F plots and control inflorescences were compared withthose held in an erect position and with others reduced to fourcentral spikelets. In the - F plots there was only very limitedlodging and erect control inflorescences were compared withthose reduced to four central spikelets. Observations were madeover a 3-week period and the pattern of seed abortion was verysimilar in all of the treatments. Approximately half of thedeveloping seeds in each spikelet were lost by abortion andthere was a similar degree of loss from all florets. The numberof abortions increased greatly with time and approx. one-thirdwere of ovaries and two-thirds were of seeds at a very earlystage of development (1–2 mm in length and without chlorophyllformation). The effect of nitrogen fertilizer was to increaseboth the number of florets per spikelet and the mean weightper seed. The results are discussed in terms of the availabilityof resources to sustain seed development and growth; it is concludedthat the high degree of abortion may be due to genetic defectsassociated with outbreeding rather than with a shortage of nutritionalfactors     

Detection of brassinosteroids in pollen of Lolium perenne L. by immunocytochemistry

Bioactive brassinosteroids have been localized in developing and mature pollen of anhydrously fixed rye-grass (Lolium perenne) by immunocytochemistry using polyclonal antibodies to castasterone generated in rabbits. Tricellular pollen fixed by freeze-substitution was also labelled in the starch granules. Study of the developmental sequence of the pollen through the microsporocyte, microspore, bicellular and tricellular stages showed that the brassinosteroids were increasingly sequestered in starch granules as the amyloplasts matured, supporting the view that these are storage organelles for these potent plant growth promoters. In bicellular pollen, heavy labelling was seen in the zone within 0.5 m of the starch granule, where stromal tissue remains. Thus, the stroma may be the site of synthesis of these compounds. During aqueous fixation, the brassinosteroids leached from the starch granules of tricellular pollen, indicating that they would be quickly available after imbibition to influence the physiology of germinating pollen. The results from high-performance liquid chromatography of dansylaminophenylboronates from partially purified extracts of freshly dehisced tricellular pollen of rye-grass showed 25-methylcastasterone may be a minor component, together with two unknown peaks. No specific binding of brassinolide to any soluble proteins extracted from tricellular rye-grass pollen was observed using the antibodies in gel electrophoresis or enzyme-linked immunosorbent assays.Abbreviations HPLC high-performance liquid chromatography - R_t retention time - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis We thank the Australian Research Council for support, the N.S.W. Department of Agriculture for rice seed, Professor K. Mori and the Zen-Noh Corporation for authentic brassinosteroid samples, Dr. I. Hudson for statistical advice, Dr. A. Bacic and Ms. I. Bonig for helpful discussion, and J.M.S. thanks Professor R.B. Knox for laboratory facilities.     

黄土性土壤固化对黑麦草生长和根系活力的影响

采用盆栽试验,研究了安塞黄绵土不同容重、不同固化剂(路邦EN-1固化剂)掺量对黑麦草生长和根系活力的影响.结果表明:黄绵土容重在1.2～1.4 9·cm-3范围内,随土壤容重的增加,黑麦草叶绿素含量、根系活力、根冠比、根生物量和植株生物量均降低;各土壤容重条件下,黑麦草叶绿素含量、根系活力、根冠比、根生物量和植株生物量均高于对照,且随着固化剂掺量的增加均呈先增加后降低的趋势.土壤容重和固化剂掺量交互作用对根生物量和总生物量的影响均显著(P＜0.05).总体来看,土壤容重1.3 g·cm-3、固化剂掺量0.15％处理下,各指标值均最高.     

Phytochelatin synthesis in response to elevated CO2 under cadmium stress in Lolium perenne L

The increasing atmospheric CO₂ and heavy metal contamination in soil are two of the major environmental problems. Knowledge of the Cd stress coping mechanisms is needed to understand the regulation of the plants’ metabolism under the increasing atmospheric CO₂ levels. Lolium perenne L. was grown hydroponically under two concentrations of atmospheric CO₂ (360 and 1000 μL L⁻¹) and six concentrations of cadmium (0-160 μmol L⁻¹) to investigate Cd uptake, Cd transportation, and variations in phytochelatin (PC) concentration. Cd concentrations in roots and shoots were decreased, but transport index (Ti) was increased under elevated CO₂ compared to ambient CO₂. Regardless of CO₂ concentrations, Cd and PC concentrations, especially the concentrations of high molecular weight PCs (PC₄, PC₅, PC₆) were higher with increasing Cd concentration in growth media and longer Cd exposure time. Under the elevated CO₂, more high molecular weight PCs (PC₄, PC₅, PC₆) in shoots and roots were synthesized compared to ambient CO₂, with higher SH:Cd ratio in roots as well. These results indicate that under elevated CO₂, L. perenne may be better protected against Cd stress with higher biomass, lower Cd concentration and better detoxification by phytochelatins.     

Synaptonemal complex formation in hybrids of Lolium temulentum x Lolium perenne (L.)

Comparisons were made between two kinds of tetraploids derived from the hybrid Lolium temulentum x L. perenne. One hybrid behaves like an autotetraploid with multivalents at first metaphase of meiosis in pollen mother cells. The other behaves like an allotetraploid, in which pairing at first metaphase is restricted to bivalents comprised of strictly homologous chromosomes. The diploidisation of the latter form is controlled by determinants located on both the normal, A chromosomes and on supernumary B chromosomes. Reconstruction of synaptonemal complexes and their elements, from serial sections through pollen mother cell nuclei examined under the electron microscope, reveals that at zygotene pairing in both forms results in multivalent formation involving non-homologous as well as homologous chromosomes. The mechanism responsible for the diploidisation is, therefore, not based on a restriction of pairing at early meiosis to homologous chromosomes but on a correction or transformation of the multivalent chromosome associations to bivalents subsequent to zygotene. The transformation is not completed until late pachytene. In the multivalent-forming tetraploid a maximum of four chromosomes are associated at first metaphase. Yet configurations of a higher valency are found at zygotene. There is, therefore, a partial transformation of multivalents even in this autotetraploid form which restricts configurations at metaphase I to homologous and homoeologous chromosomes only. In both hybrids some homologous bivalents are not the product of resolution of multivalents but result from two-by-two pairing from the beginning of zygotene.     

Influence of Genotype and Mineral Nutrition on the Distribution of Growth within Plants of Lolium perenne L. grown in Soil

Genotypes of Lolium perenne were grown with two levels of fertilizerapplication. Using exponential growth-rates and parameters derivedfrom them, the rate of growth of each genotype was partitionedinto the rates of initiation of new roots and tillers, and thegrowth of the individual roots and tillers after initiation.The growth of the individual roots was further analysed by measuringchanges in diameter and length of the main root, and the growthin the branches of the main root. The genotypes varied in their response to additional mineralnutrition. The greater the increase in the rate of shoot growthfor a genotype, the greater was its increase in the rate oftiller initiation, the smaller was the increase in the sizeof its tillers, and the greater was the decrease in its rateof root relative to shoot growth. Within a population of genotypes growing with the same levelof mineral nutrition, the greater the rate of shoot growth ofa genotype, the greater was the rate of initiation of new tillersand, at a low level of mineral nutrition, the smaller the sizeof tillers. With a higher level of mineral nutrition, the higherthe rate of tiller production, the smaller or larger was tillersize, depending upon environmental factors other than mineralnutrition. At both levels of mineral nutrition, the greaterthe rate of shoot growth, the smaller was the rate of root growthrelative to shoot growth, due to relatively less growth takingplace in the branches of the main root.