Use of ryegrass strips to enhance biological control of aphids by ladybirds in wheat fields

Abstract Non‐crop habitats may play a vital role in conservation biological control. This study tested the effect of ryegrass (Lolium multiflorum L.) strips on aphid and ladybird populations in adjacent winter wheat fields. The field experiment was conducted in three ryegrass‐margin wheat plots and three control plots in 2010 in North China. In spring, the same aphid species, Sitobion miscanthi (Takahashi), was found in both the ryegrass strips and wheat plots. The population density of ladybirds in the ryegrass strips (3.5 ± 0.9/m²) was significantly higher than in the wheat plots (1.5 ± 0.5/m²). We cut the ryegrass, forcing the ladybirds to migrate to the wheat fields. Three and eight days after cutting the ryegrass, the aphid numbers in the ryegrass‐margin wheat plots decreased significantly: they were 19.9% and 53.6%, respectively, lower than in control plots. In the early period of ladybird population development, the percentage of larvae was greater in the ryegrass‐margin wheat plots than in controls, and the peak number of pupae in the ryegrass‐margin wheat plots occurred 5 days earlier than in the control plots. The results suggest that ryegrass strips may promote the development of ladybird populations. Cutting ryegrass can manipulate ladybirds to enhance biological aphid control in wheat fields. The efficiency of this management approach is discussed.     

Development and implementation of a multiplexed single nucleotide polymorphism genotyping tool for differentiation of ryegrass species and cultivars

Perennial ryegrass (Lolium perenne L.) and Italian ryegrass (Lolium multiflorum Lam.) are important temperate forage grasses which are closely related, generating fertile interspecific hybrids. All groups are represented by multiple cultivars in the commercial pasture seeds market. Due to the close taxonomic relationship between the two species, differentiation based on morphophysiological criteria is not always readily achievable. In addition, an obligate outbreeding reproductive habit produces high levels of individual heterozygosity and intrapopulation diversity, which presents problems for discrimination between cultivars. Molecular genetic marker polymorphism provides an effective means of addressing these challenges. An iterative process of resequencing from loci distributed across the perennial ryegrass genome was used to identify single nucleotide polymorphism (SNP) markers, which were then validated and formatted in a highly multiplexed (384-plex) assay system. SNP genotyping was then performed across samples of 48–192 individuals from a total of 27 ryegrass cultivars (19 of perennial ryegrass, seven of Italian ryegrass and one hybrid cultivar). SNP markers from perennial ryegrass exhibited a high level of transfer to Italian ryegrass. Data analysis permitted quantification of intra- and inter-species diversity, as well as discrimination between cultivars within each species, including diploid and autotetraploid cultivars of perennial ryegrass. Lower levels of SNP-based diversity were detected in Italian ryegrass than in perennial ryegrass. A neighbour-joining tree based on genetic distance analysis located a hybrid cultivar to an intermediate position between the two species-specific cultivar groups. The resulting catalogue of ryegrass cultivars will provide support for the processes of cultivar accreditation and quality assurance.     

Tolerance to ryegrass mosaic virus and its inheritance

Plant yield within and between four cultivars of perennial ryegrass infected with ryegrass mosaic virus (RMV) was closely related to symptom severity. Distribution of symptom severity was continuous in four perennial ryegrass and four Italian ryegrass cultivars infected with a severe RMV isolate, and also in another perennial ryegrass cultivar infected with a severe isolate of the virus, a mild one and one of intermediate severity. Symptom expression was polygenically inherited in both Italian (cv. RvP) and perennial (cv. S.24) ryegrass. Both additive and non-additive genetic variation was present in RvP, but the variation in S.24 was additive only. No significant maternal inheritance was present in either species.     

Selection of perennial and Italian ryegrass plants resistant to ryegrass mosaic virus

Perennial ryegrass plants collected from fields and Italian ryegrass plants grown from seed were selected for resistance to infection by ryegrass mosaic virus (RMV) by repeated manual inoculation. Two of 108 perennial ryegrass plants and one of 150 Italian ryegrass plants were symptomless after seven and nine inoculations respectively. These three plants were propagated vegetatively. Plants of the two perennial ryegrass clones showed no symptoms after further manual inoculations with the initial isolate of RMV, or with an inoculum from infected plants collected from several fields, or after inoculation by viruliferous mites. Electron microscopy and back tests indicated that the plants were virus free. Some plants of the selected Italian ryegrass clone became infected after a further inoculation with mites or sap, but fewer than similarly inoculated unselected plants.     

A novel DNA-based diagnostic test for the detection of annual and intermediate ryegrass contamination in perennial ryegrass

Perennial ryegrass (Lolium perenne L.) is a preferred choice for the turf grass industry due to its ability to provide a durable turf cover. Genetic or physical contamination of annual (L. multiflorum Lam.) or intermediate (L. hybridum) ryegrass species in perennial ryegrass is one of the major problems affecting the grass seed industry. At present, seedling root fluorescence (SRF), a biochemical marker, is used for the detection of annual ryegrass contamination. Due to the unreliability of the SRF test, the seed industry is seeking an alternative, more reliable and accurate detection method. Currently, there are no DNA tests available in ryegrass for detecting contamination with annual and intermediate ryegrass types. We developed a novel quantitative polymerase chain reaction (Q-PCR)-based DNA test for the detection of annual and/or intermediate ryegrass types in perennial ryegrass. This DNA test was designed using an insertion/deletion (InDel) site in the LpVRN2_2 (Vernalization 2) gene, which is one of the several genes controlling vernalization in ryegrass. The new DNA test is more reliable, accurate and cost-effective in detecting contamination, with a high sensitivity of 0.04% in a sample size of 5,000 seeds. Use of larger sample sizes (12.5-fold higher compared to SRF test) provided additional accuracy in detecting the level of contamination. The method has produced consistent results in 68 perennial, 26 annual and 14 intermediate ryegrass lines.     

黑麦草生长过程中有机酸对镉毒性的影响

研究了低分子量有机酸草酸、柠檬酸、乙酸及高分子量有机酸胡敏酸对黑麦草(Lolium Loinn)生长过程中Cd毒性的影响.结果表明,随着低分子量有机酸浓度增加,Cd毒性有所增强,致使黑麦草中的叶绿素含量降低及黑麦草的生物量降低,递降顺序是草酸＜乙酸＜柠檬酸.而施入胡敏酸后,Cd毒性逐渐减弱,黑麦草中的叶绿素含量及黑麦草生物量逐渐增加.对低分子量有机酸而言,无论迁移到黑麦草茎叶中,还是迁移到黑麦草根系中的Cd,随着施入的有机酸浓度增加,增加顺序为柠檬酸＞乙酸＞草酸.对胡敏酸而言,迁移到黑麦草茎叶和根系中的Cd,随着施入的胡敏酸浓度增加,Cd含量减少,说明其具有降低Cd毒性的作用.另外,根系中Cd含量明显高于茎叶中Cd含量,由此得知,黑麦草根系对Cd有较强的富集作用,并阻止Cd向茎叶中迁移.     

Infection Biology of Bacterial Wilt of Forage Grasses

Infection of perennial ryegrass (Lolium perenne L.), Italian ryegrass (Loliummultiflorum L.), and timothy (Phleum pratense L.) by Xanthomonas campestris pv. graminis and Xanthomonas campestris pv. phlei occurred mainly via wounds rather than natural openings. Nevertheless, bacteria were detected by isolation and immunofluorescence in plants sprayed with the pathogen without prior wounding and in plants in which intact ears had been dipped in inocula. High concentrations of bacteria were observed around the stomata of perennial ryegrass and timothy by scanning electron microscopy 48 h after inoculation. Perennial ryegrass and Italian ryegrass and individual plants of ryegrass and timothy differedin susceptibility to the pathogens.     

Construction of a primary RH panel of Italian ryegrass genome via UV-induced protoplast fusion

Symmetric and asymmetric somatic hybrids were produced via protoplast fusion between common wheat ( TRITICUM AESTIVUM L.) cv. "Jinan 177" and Italian ryegrass ( LOLIUM MULTIFLORUM Lam.). The ryegrass without or with UV irradiation was used as a donor, providing a small amount of chromatin. In these somatic hybrids, most ryegrass chromosomes have been confirmed preferential elimination and the somatic hybrid calli and plants showed wheat-like morphology. Some of the hybrid lines were used for the analysis of distribution and heredity of donor DNA in the hybrid genome and the possibility of establishing a radiation hybrid (RH) panel of the ryegrass in the present experiment. These hybrids, subcultured for two and three years, retained the ryegrass DNA examined by RFLP and GISH analysis, respectively. Distribution of the ryegrass DNA in the wheat genomes of 20 single-cell individuals, randomly selected from hybrid cell lines produced, were analyzed by 21 ryegrass genome specific SSR markers. The average frequencies of molecular marker retention in symmetric hybrid lines (UV 0), as well as asymmetric hybrid lines from UV 30 s and 1 min were 10.88, 15.48 and 33.86, respectively. It was suggested that the UV dose increased the introgression of donor DNA into wheat genome. The ryegrass SSR fragments in most asymmetric hybrid cell lines remained stable over a period of 2 approximately 3 years. This revealed that those asymmetric somatic hybrids are suitable for the introgression of ryegrass DNA into wheat, and for RH panel and RH mapping.     

Decreased severity of ryegrass mosaic virus after passage through resistant perennial ryegrass

After exposure to infection in the field, the proportion of plants showing distinct symptoms of ryegrass mosaic virus (RMV) was less in perennial than in Italian ryegrass. The perennial ryegrass cv. Mascot had a smaller proportion of plants with symptoms than cv. S.23. Far milder symptoms were induced in test plants by RMV from naturally infected perennial ryegrass plots than from Italian ryegrass plots. Within perennial ryegrass, RMV from cv. Mascot caused milder symptoms than that from cv. S.23. Severe RMV isolated from Italian ryegrass cv. Trident (RMVT) became milder after one passage through cv. Mascot, although not as mild as RMV obtained from field plots of cv. Mascot (RMVM). Families from two highly resistant perennial ryegrass clones and two randomly selected clones of cv. S.23 crossed in all possible combinations varied in symptom severity when inoculated with RMVT but not when inoculated with RMVM. Families inoculated with RMVT also yielded virus which varied in the severity of symptoms induced in test plants, families with severe symptoms yielding severer virus. Thus, much of the variation in the resistance of these clones could be attributed to infection with RMV of differing severity. Resistance was controlled by several genes which were mainly additive in their effect.     

Use of white clover as an alternative to nitrogen fertiliser for dairy pastures in nitrate vulnerable zones in the UK: productivity, environmental impact and economic considerations

Perennial ryegrass and perennial ryegrass/white clover permanent dairy pastures are compared with respect to productivity, environmental impact and financial costs in nitrate vulnerable zones (NVZ) in the UK. With appropriate management, and utilisation of recommended perennial ryegrass and white clover cultivars, white clover is likely to stabilise at around 20% of total dry matter production in a mixed pasture. Plant dry matter production and milk production from a perennial ryegrass/white clover pasture are likely to be similar to that from a perennial ryegrass pasture receiving 200 kg N ha⁻¹ annum⁻¹ and around 70% of that obtained with perennial ryegrass supplied with 350–400 kg N ha⁻¹ annum⁻¹. Nitrate, phosphorus and methane losses from the system and decreases in biodiversity relative to a grazed indigenous sward are likely to be similar for a perennial ryegrass/white clover pasture and a perennial ryegrass pasture receiving 200 kg N ha⁻¹ annum⁻¹: nitrate leachate from both systems is likely to comply with European legislation. Greenhouse gas emissions resulting from nitrogen (N) fertiliser production would be avoided with the perennial ryegrass/white clover pasture. Within NVZ stocking rate restrictions, white clover can provide the N required by a pasture at a lower financial cost than that incurred by the application of N fertiliser.     

Chromosomal rearrangements differentiating the ryegrass genome from the Triticeae, oat, and rice genomes using common heterologous RFLP probes

An restriction fragment length polymorphism (RFLP)-based genetic map of ryegrass (Lolium) was constructed for comparative mapping with other Poaceae species using heterologous anchor probes. The genetic map contained 120 RFLP markers from cDNA clones of barley (Hordeum vulgare L.), oat (Avena sativa L.), and rice (Oryza sativa L.), covering 664 cM on seven linkage groups (LGs). The genome comparisons of ryegrass relative to the Triticeae, oat, and rice extended the syntenic relationships among the species. Seven ryegrass linkage groups were represented by 10 syntenic segments of Triticeae chromosomes, 12 syntenic segments of oat chromosomes, or 16 syntenic segments of rice chromosomes, suggesting that the ryegrass genome has a high degree of genome conservation relative to the Triticeae, oat, and rice. Furthermore, we found ten large-scale chromosomal rearrangements that characterize the ryegrass genome. In detail, a chromosomal rearrangement was observed on ryegrass LG4 relative to the Triticeae, four rearrangements on ryegrass LGs2, 4, 5, and 6 relative to oat, and five rearrangements on ryegrass LGs1, 2, 4, 5, and 7 relative to rice. Of these, seven chromosomal rearrangements are reported for the first time in this study. The extended comparative relationships reported in this study facilitate the transfer of genetic knowledge from well-studied major cereal crops to ryegrass.     

氮锌硒肥配合施用对白三叶的固氮作用与氮转移的影响

在湖北省宜昌县百里荒草场山地黄棕壤上配合施用氮锌硒肥,研究其对混播白三叶,混播黑麦草及单播黑麦草的干重及混播白三叶的固氮作用和氮转移的影响,试验结果表明：（1）氮锌硒肥配合施用,混播黑麦草的干重均高于相应处理的单播黑麦草,混播牧草和单播黑麦草重最高的处理都是N46Zn0Se5,其干重辚25．38 g／盆和19．93g/盆。（2）施氮对混播白三叶,混播黑麦草及单播黑麦草的生长有明显的促进作用,施锌,硒对混播白三叶,混播黑麦草及单播黑麦草的生长作用不明显。（3）混播白三叶氮素的主要来源是固氮作用,占全氮产量的57．6000％－77．258％。（4）混播白三叶固定氮的转移量只占混播黑麦草的全氮产量的0．316％－12．251％,通过正交方差分析发现,适量氮肥（N30mg/kg)促进固定氮的转移,高量氮肥（N46mg/kg)抑制固定氮的转移。     

Indirect Compartmental Analysis of Copper in Live Ryegrass Roots; Comparison with Model Systems

The technique of indirect compartmental analysis of ⁶⁴Cu elutionmeasurements was applied to cellulose discs, a ryegrass (Loliumperenne L. cv. Premo) root cell wall isolate and live and deadroots of whole ryegrass seedlings. Curves of logarithm countsremaining in the material versus time resolved into four phasesin each case. The half-time of exchange of the slowest compartmentranged from 3.6 to 66.1 h for cellulose discs and live ryegrassroots, respectively. Plots of logarithm efflux versus time againresolved into four phases for cellulose discs, isolated rootcell wall, and dead ryegrass roots; the efflux of these materialsobeyed first order kinetics. In live ryegrass roots the plotof logarithm efflux versus time could not be resolved beyondthe initial curve; efflux from live ryegrass roots did not obeyfirst order kinetics. A full compartmental analysis of copperin live ryegrass roots could not be performed. It is suggestedthat, in live ryegrass roots, cell wall adsorption sites areresponsible for a wide continuous range of half-time of exchangevalues which overlie the elution curves of the vacuolar andcytoplasmic compartments. The technique of indirect compartmentalanalysis artificially splits the total elution curve into fourdiscrete compartments, the slowest of which has contributionsfrom both the vacuole and cell wall. Key words: Copper efflux, cell wall, ryegrass     

THE TRANSMISSION BY MITES, HOST-RANGE AND PROPERTIES OF RYEGRASS MOSAIC VIRUS

A virus that causes chlorotic streaks on ryegrass leaves was transmitted by the eriophyid mite Abacarus hystrix (Nalepa). Virus-free mites acquired the virus in 2 hr. feeding on infected ryegrass and the proportion that became infective increased with increased feeding time up to 12 hr.; vectors lost infectivity within 24 hr. of leaving the infected leaves. All instars of A. hystrix transmitted the virus.
The virus was transmitted by manual inoculation of sap to other species of Gramineae, including oats, rice, cocksfoot and meadow fescue, but none of these hosts seemed to contain as much virus as ryegrass; their saps did not precipitate specifically with antiserum prepared against the virus in ryegrass, whereas sap from infected ryegrass precipitated up to a dilution of 1/32. Infective sap of S22 Italian ryegrass contained flexuous rod-shaped particles; the dilution end-point of the virus was about 1 in 1000; the virus was inactivated when held for 10 min. at 60°C. and most of its infectivity was lost after 24 hr. at room temperature.     

浮床黑麦草对城市生活污水氮循环细菌繁衍和脱氮效果的影响

通过设施大棚内容积为1.5m3的人工模拟池试验,研究了浮床黑麦草对模拟城市生活污水氮循环细菌繁衍和脱氮效果的影响。通过研究,阐明浮床植物去除污染水体氮素的可能途径。研究结果表明:浮床黑麦草对模拟城市生活污水总氮和氨氮的去除效果分别达到了31.6%和43.0%;浮床黑麦草根际和根系正下方是各类氮循环细菌生长的最佳区域;浮床黑麦草处理有效地提高了系统氮循环细菌的数量,16d的试验结束时细菌总数(A,单位为CFU.mL-1)达到最大值,其lg(A/(CFU.mL-1))增加至8.82,各类氮循环细菌比对照高3-5个数量级;同时,浮床黑麦草处理显著提高了氮循环细菌的群落多样性,系统内氨化菌、硝化菌、亚硝化菌和反硝化菌共存;明确了浮床黑麦草的吸收同化和氮循环细菌的生物脱氮是浮床黑麦草净化水质的两个重要途径。     

混播草地不同种群再生性的研究

在不同刈割频率和时间尺度下 ,对混播草地多年生黑麦草 (Lolium perenne)分蘖数和叶片生长、白三叶 (Trifoliumrepens)分枝数和匍匐茎生长及不同种群年产量和组分进行了连续 3年的监测研究 .结果表明 ,刈割能刺激黑麦草叶片、白三叶匍匐茎生长和分枝数发生 ,保持混播草地黑麦草和白三叶的适宜比和稳定共存 ,提高草地年生产力 ,但不同刈割频率和刈割时间对其影响差异不显著 (P >0 .0 5 ) .黑麦草叶片生长对 6月刈割效果比 8月明显 ,而白三叶匍匐茎生长则与之相反 ,黑麦草产量主要取决于叶片生长 ,白三叶产量主要取决于匍匐茎分枝数 .刈割的黑麦草、白三叶产量组分比分别为 5 0 %、15 % ,比试验前约低 10 %、5 % ,而CK为 39%、6 % .     

Growth of zinnia,Italian ryegrass,and alfalfa and their remediation effects in diesel oil-contaminated soils

Abstract

Our objective in this study was to compare the growth of zinnia, Italian ryegrass, and alfalfa, and their remediation effects in oil-contaminated soils. The soils were prepared by mixing 2, 4, or 8% diesel oil by weight with soil. The plant height and dry weights of shoots and roots were highest for zinnia in the 2 and 4% oil treatments, and highest for Italian ryegrass in the 8% oil treatment. The reduction ratios in soil total petroleum hydrocarbons concentration (TPH) for 3 plants were lower in the 4 and 8% oil treatments than those in the 2% treatment. The reduction ratios for Italian ryegrass and zinnia contaminated with 2, 4, and 8% diesel oil treatments were significantly higher than those for alfalfa and the non-cultivation treatment at 45?days after sowing, and there were no significant differences in reduction ratios between Italian ryegrass and zinnia. The reduction ratio of soil TPH concentration brought about by zinnia was also comparable to that of Italian ryegrass. Therefore, we conclude that zinnia shows growth and remediation effects that are equivalent to those of Italian ryegrass, in soils contaminated with less than 8% oil.     

Black cutworm (Lepidoptera: Noctuidae) larval emigration and biomass in mixtures of endophytic perennial ryegrass and Kentucky bluegrass.

Studies examined the possibility that mixtures of endophytic perennial ryegrass and Kentucky bluegrass provide resistance against larvae of the black cutworm, Agrotis ipsilon (Hufnagel). We hypothesized that resistance against A. ipsilon in such stands would stem from the influence of Kentucky bluegrass on A. ipsilon growth and behavior rather than the influence of endophytic perennial rvegrass. In replicated greenhouse experiments, black cutworm larvae initially emigrated more quickly from pots containing monocultures of endophytic perennial ryegrass than from Kentucky bluegrass monocultures or polycultures of Kentucky bluegrass and endophytic perennial ryegrass. However, biomass of emigrating larvae decreased linearly as the proportion of Kentucky bluegrass increased. Turfgrass mixtures containing endophytic perennial ryegrass and Kentucky bluegrass may provide resistance against A. ipsilon mainly through the physiological effects of Kentucky bluegrass on A. ipsilon growth and development, but possibly through the influence of endophytic perennial ryegrass on A. ipsilon movement and foraging behavior as well.     

东北地区不同小麦品种对黑麦草的化感作用

以东北地区33个不同来源的小麦品种为研究对象,采用琼脂共培法,评价了不同小麦品种对黑麦草所产生的化感作用.通过分析不同小麦品种对黑麦草根长、苗高、根干重及苗干重的影响,探讨不同小麦品种对黑麦草化感作用的差异,从而筛选出具有较强化感潜力的小麦品种.结果表明,不同小麦品种对黑麦草根长、苗高、根干重及苗干重的影响存在显著差异.利用RI值作为化感作用的指标,结合聚类分析方法,可将这33个小麦品种按化感能力的强、中、弱分成3类;其中龙幅麦9号、龙幅麦13号、锦麦2003和小冰麦33号为化感能力较强的品种.     

A TERMINAL FLOWER1-like gene from perennial ryegrass involved in floral transition and axillary meristem identity

Control of flowering and the regulation of plant architecture have been thoroughly investigated in a number of well-studied dicot plants such as Arabidopsis, Antirrhinum, and tobacco. However, in many important monocot seed crops, molecular information on plant reproduction is still limited. To investigate the regulation of meristem identity and the control of floral transition in perennial ryegrass (Lolium perenne) we isolated a ryegrass TERMINAL FLOWER1-like gene, LpTFL1, and characterized it for its function in ryegrass flower development. Perennial ryegrass requires a cold treatment of at least 12 weeks to induce flowering. During this period a decrease in LpTFL1 message was detected in the ryegrass apex. However, upon subsequent induction with elevated temperatures and long-day photoperiods, LpTFL1 message levels increased and reached a maximum when the ryegrass apex has formed visible spikelets. Arabidopsis plants overexpressing LpTFL1 were significantly delayed in flowering and exhibited dramatic changes in architecture such as extensive lateral branching, increased growth of all vegetative organs, and a highly increased trichome production. Furthermore, overexpression of LpTFL1 was able to complement the phenotype of the severe tfl1-14 mutant of Arabidopsis. Analysis of the LpTFL1 promoter fused to the UidA gene in Arabidopsis revealed that the promoter is active in axillary meristems, but not the apical meristem. Therefore, we suggest that LpTFL1 is a repressor of flowering and a controller of axillary meristem identity in ryegrass.