Mapping of EST-derived CAPS markers in Italian ryegrass (Lolium multiflorum Lam.)

New molecular markers derived from expressed sequence tag (EST) sequences were mapped on linkage maps of Italian ryegrass by a two-way pseudo-testcross strategy. cDNA sequences were obtained from various tissues of Italian ryegrass ( Lolium multiflorum ) and converted into cleaved amplified polymorphic sequence (CAPS) markers. Of 260 EST primer pairs that amplified a single band, 74 generated bands that showed clear polymorphisms among individuals of an F₁ mapping family. Of the 74 polymorphic marker loci, 69 were mapped on an Italian ryegrass linkage map previously constructed using amplified fragment length polymorphism (AFLP), restriction fragment length polymorphism (RFLP), and simple sequence repeat (SSR) markers. The newly-developed EST-CAPS markers would be useful as an efficient tool to identify genetic markers and to identify candidate genes for quantitative trait loci (QTLs) associated with important traits in Italian ryegrass.     

Specialization of crown rust (Puccinia coronata Corda) on clones of Italian ryegrass (Lolium multiflorum Lam.)

Summary Cultures of crown rust (Puccinia coronata Corda) from a mixed uredospore population obtained from plants in 16 localities in England and Wales were multiplied on four of 10 initially resistant clones of Italian ryegrass (Lolium multiflorum Lam.). Only two of the four cultures were found to be most pathogenic on the clones on which they had been multiplied. One clone became very susceptible to its own culture but the other became only moderately susceptible. Clone/culture interactions occurred which were not obviously related to the clone of origin of the culture. Thus, there was considerable genetic diversity in the crop which would tend to limit the multiplication of new races. There was a strong correlation between visual score for susceptiblity and uredospore production, showing the value of visual scores for resistance breeding.     

Breeding of Italian Ryegrass (Lolium multiflorum Lam.) for a low nitrate concentration by seedling test

In Japan, nitrate poisoning in ruminantscaused by the accumulation of nitrate inforage crops is a serious concern. In thisstudy, 3 cycles of phenotypic recurrentselection for nitrate concentration on adry matter basis were conducted for Italianryegrass (Lolium multiflorum Lam. cv.Nioudachi) to develop a breeding methodusing a seedling test. The seedling testinvolved the nitrate analysis of a shootfrom a plant grown for 6 or 8 weeks in thepresence of 50 mM KNO₃. The selectionintensity was approximately 0.07 for eachcycle. The realized heritability of thethird generation was calculated to be 0.21for seedlings and 0.57 for adult plants. Ina pot experiment, the nitrate concentrationof the adult plants of the third generationwas found to be 60% of the value for theoriginal population at an early headingstage. The reduction is related to theincrease in dry matter (DM) content as wellas the decrease in nitrate concentration ona fresh matter basis. The original andselected populations did not differ in theheading date. The concentrations of K, Nand P in the third generation decreasedwith the increase of DM content, whereas Caand Mg concentrations remained constant. Variation in the nitrate concentration wasfound among varieties on the market. Inconclusion, the ability to accumulatenitrate is a quantitative genetic trait ofItalian ryegrass and large-scale selectionfor the breeding of low nitrate populationsis possible using a seedling test.     

Origin of Westerwolths ryegrass (Lolium multiflorum westerwoldicum)

Summary In the past century, all the grass seed required for the Netherlands was imported.About 1900, however, the seed production of the annual Westerwolths ryegrass (Lolium multiflorum westerwoldicum) was introduced. The local variety was probably obtained by harvesting seed producing plants from Italian ryegrass, sown in spring and sowing again in the next year in spring. In this way a local variety of the seed type originated.     

The use of hedges to reduce winter wheat losses caused by Italian ryegrass (Lolium multiflorum)

We hypothesized that short duration plant interference aiming to change mainly light intensity and red:far red ratio during crop establishment in Italian ryegrass-infested winter wheat fields, could hinder the development of Italian ryegrass and thus reduce its effect on wheat yield. To test this hypothesis, wheat was planted between previously established live (low red:far red ratio) or dead (high red:far red ratio), barnyardgrass or maize, plant hedges. Experimental results demonstrated that the presence of live or dead plant hedges during the first 30 days of crop establishment and also hedge orientation were important factors regulating weed and crop biomass production and competitive relationships. In barnyardgrass hedge treatments wheat yield was improved up to 67% and Italian ryegrass production was reduced by more than 20%. In plots with maize live hedges oriented N–S the biomass production of wheat was independent of production of Italian ryegrass. Data presented here suggests that there is room for developing weed control technologies on the basis of understanding photosensory processes of weed and crop species.     

Tetraploid Westerwolths ryegrass

Summary Germinated seeds of the annual Westerwolths ryegrass were treated with colchicine-solutions of 0.05 to 0.4% at a temperature of 29°C in order to obtain autotetraploids. The best results were obtained after treatment for 2 hours with 0.1 and 0.2% solutions or 4 hours with 0.05%. By these procedures about 8% of the treated seeds produced mixoploid or tetraploid mature plants. A preliminary progeny test was performed with seed of outstanding C₁-plants.In spaced plants and in drilled rows the dry matter production of these C₂-families was on average equally as high as that of the most productive original diploid variety. The proportion of leaves was higher in both the first and in the second cut, while drought resistance was considerably better. The tetraploids came later into ear, tillering ability was smaller and mildew attack was slightly heavier. In samples from drilled and from space-planted rows seed production per inflorescence was found to be higher in the tetraploids than in the diploids. The seed of the tetraploids was larger.From the data available it is concluded that chromosome doubling offers favourable possibilities for the improvement of Westerwolths ryegrass. Some suggestions for a breeding programme are given.     

Inheritance of anther-culture response in perennial ryegrass (Lolium perenne L.)

Genetic control of the capacity to respond to anther culture in perennial ryegrass was studied in F₁ offspring from crosses between 11 clones selected for anther-culture response (‘inducers’) and 10 clones selected from breeding material on the basis of good agronomic performance. Large differences in anther-culture response were observed between the two types of parent, with inducer clones producing an average of 10.7 green plants per 100 anthers, compared with only 0.3 for breeding clones. Hybrid populations produced an average of 2.2 green plants per 100 plated anthers, which is 7.3 times the response of the breeding material. This improvement was mainly due to a 9.4-fold increase in the percentage of green plants regenerated from hybrid populations to 4.7% compared to an average of 0.5% from breeding clones. Most of the GCA (general combining ability) in the experiment was contributed by the breeding material, constituting 55.8, 100.0 and 36.7% of genetic variation among hybrids for embryo formation, regeneration and green plant percentage, respectively. Any remaining genetic variation among hybrids was predominantly due to SCA (specific combining ability) effects, with percentages of 44.2 and 63.3%, respectively, for embryo and green plant formation. These results are discussed with respect to the possible exploitation of genes controlling anther-culture response for haploid production in breeding programmes of perennial ryegrass.     

Cytogenetic Studies of Hybrids between Festuca gigantea Vill. and Lolium multiflorum Lam.

The meiotic behaviour of the hybrid between Festuca gigantea (2n – 6x = 42) and Festuca gigantea (2n = 6x = 42) indicates distinct structural differences between the two species. These differences are also apparent in the degree of chromosome pairing observed in Lolium multiflorum×F. gigantea compared with previous reports on the L. multiflorum×F. arundinacea hybrids. Although the L. multiflorum×F. gigantea 8x amphiploid com Dines the complementary characters of the two species and is agronomically interesting, there are some irregularities in meiotic behaviour that could affect the stability of the amphiploid. Seed fertility in the amphiploid is high and preliminary studies show evidence of a high degree of self-fertility. The pentaploid hybrid between autotetraploid L. multiflorum×F. gigantea is sufficiently fertile to be used as the pollen plant in crosses with diploid L. multiflorum (BC₁). Backcrossing the BC₃ hybrid to L. multiflorum results in mainly diploid progeny. The possibilities, of using this crossing scheme to introgress F. gigantea characters into L. multiflorum is discussed as an alternative approach to amphiploid breeding as a means o: combining specific complementary characters of the two species.     

钙对多花黑麦草种子萌发和幼苗生长的影响

为探明多花黑麦草(Lolium multiflorum)种子在钙(Ca)盐胁迫下的耐受性,研究了不同Ca^ 2+浓度(0,5,10,20,40,100 mmol ·L^-1 )对多花黑麦草种子萌发和幼苗生长的影响,并利用隶属函数综合评价出适宜多花黑麦草生长的浓度。结果表明:随着Ca 2+浓度的增加,发芽势、发芽率、发芽指数、根长和苗长呈下降趋势,苗、根的干重和鲜重呈先上升后下降趋势,根苗比、根冠比、盐害率、根抑制率和苗抑制率呈上升趋势。Ca ^2+浓度为5 mmol ·L^-1 条件下,幼苗和幼根的干重和鲜重都达到了最大值。在各浓度处理之间根苗比和根冠比差异不显著( p >0.05)。隶属函数综合评价得出适宜多花黑麦草种子萌发的Ca^2+浓度为5 mmol ·L^-1 ,为高Ca^2+土壤条件下栽种多花黑麦草提供科学依据。     

Testing perennial ryegrass (Lolium perenne L.) as spaced plants in swards

Summary A method of testing spaced plants in swards of another grass crop is described. The procedure provides information on sward performance at each stage of the breeding scheme. A large number of entries may be included, together with whatever cutting frequency.When used for perennial ryegrass, the method favours the selection of productive and persistent plants.     

Cross compatibility between diploid and tetraploid perennial ryegrass (Lolium perenne L.)

Summary A number of crosses were made between diploid and tetraploid Lolium perenne plants in order to determine the degree of cross compatibility between the two different ploidy levels. The range of hybridization undertaken involved diploidxdiploid, and tetraploid x tetraploid control crossings, diploid x tetraploid crosses, tetraploid x diploid crosses and mixed pollinations. The seed set, the germination capacity of resultant hybrid seeds, and the chromosome constitution of derived seedlings was determined. In addition attempts were made to culture 12 day-old hybrid embryos from the diploid x tetraploid and reciprocal crosses.The crossing results obtained indicated no barrier to fertilization between diploids and tetraploids, but the irregular and poor development of the seed accompanied by much reduced germination, indicated unsatisfactory endosperm establishment of large numbers of triploids, as confirmed by the result of culturing embryos dissected from 12-day old seeds.In preliminary studies undertaken to determine the extent to which diploid and tetraploid ryegrass varieties intercross when grown in close proximity for seed production, Griffiths and Pegler (1966) observed a very low incidence of triploids amongst the progenies of diploid plants exposed to the pollen of tetraploid plants and also amongst the progenies of tetraploid material exposed to the pollen of diploid plants.In these and subsequent studies it was noted that only a very small proportion of the so-called fully formed seeds derived from diploid x tetraploid crosses did actually germinate. When, in 1964, propagules of clones of S.24 perennial ryegrass, well separated from one another, were placed in drills of the tetraploid perennial ryegrass variety Reveille, the proportion of florets which formed caryopses, and of caryopses which germinated was as follows (Table 1).The data (Table 1) clearly indicate that a considerable proportion of the S.24 florets had been fertilized by 2n pollen and had formed caryopses, but most of these had proved to be defective. As noted in the previous studies, the frequency of triploid seedlings was low, thus suggesting incompatibility between the n and 2n gametes for the production of viable zygotes.Of the total progenies classed as tetraploids in the early seedling stage, 80% proved to be ryegrass x tall fescue F₁ hybrids. These arose as a result of free crossing with     

Suspension culture performance in commercial varieties of perennial ryegrass (Lolium perenne L.)

Summary Suspension culture performance in commercial varieties of perennial ryegrass was studied to assess the effect of variety on suspension culture response and plant regeneration. 179 suspension cultures were established from embryos of mature seeds of 21 varieties and one breeding population. Of these, 123 suspensions were morphogenic (21 varieties) and 66 suspensions (18 varieties) regenerated green plants. A number of suspension lines, originating from two different suspensions, retained the capacity for green plant formation for almost four years. Replicates performed with seed lots of different ages indicated that suspensions initiated from young seeds (1 year) were of better quality than suspensions initiated from older seeds (2–4 years). Varieties differed in their capacity to form morphogenic suspensions and suspensions capable of regenerating green plants, although the effect of variety was relatively small. It was concluded that responsive genotypes can be found within most varieties of Lolium perenne.     

Aneuploids of perennial ryegrass (Lolium perenne)

Summary Aneuploid plants of perennial ryegrass (Lolium perenne L.) with 2n=15 to 30 chromosomes were obtained by crossing a near-triploid (2n=3x+1=22) with a diploid or on open-pollination with diploids and tetraploids. Aneuploids occurred with a frequency of 83% in near triploid × diploid progeny and 92% on open-pollination with diploid and tetraploid plants. Aneuploid plants with 15 to 18 chromosomes resembled diploids in morphology and those with 19 to 30 chromosomes were akin to tetraploids. Meiotic studies suggested that most aneuploid plants resulted from transmission of aneuploid egg cells (n=8 to 23). Aneuploid plants with 2n=27 to 30 chromosomes in the progeny of 22×14 cross originated from unreduced egg cells. Plants with 19 to 21 chromosomes were recovered only by immature seed culture. Aneuploid plants with 26 to 30 chromosomes and triploids (2n=21) had higher pollen fertility and bigger seeds than plants with 15 to 22 chromosomes.     

Association of agronomic traits with isozyme loci in perennial ryegrass (Lolium perenne L.)

Summary Inbred lines possessing different genotypes at three isozyme loci, PGI-2, GOT-3 and ACP-1, were produced by two generations of selfing from two contrasting cultivars of perennial ryegrass. Four separate F₂ populations were obtained by selfing or crossing F₁ plants from crosses between cultivar inbred lines. F₂ plants were scored for genotype at the three isozyme loci and for eight agronomic traits. The three isozyme loci showed independent segregation confirming that they belonged to separate linkage groups. A consistent association was observed between water soluble carbohydrate content and genotype at the PGI-2 locus. Some association was also detected between genotype at the ACP-1 locus and heading date. The relevance of these observations to ryegrass breeding programmes is discussed.     

Assessment of perennial ryegrass (Lolium perenne L.) for breeding. I Freezing tolerance

Summary Assessments of freezing tolerance, estimated in terms of temperature at which 50% mortality occurs (=LT₅₀), were obtained for 86 Lolium perenne accessions using a glycol bath test on naturally hardened field plants. Significant correlations were obtained between LT₅₀ and both heading dates of accessions and minimum temperature of the coldest month near their sites of origin. The effects of temperature and reproductive development on the hardening/dehardening of plants and their growth after freezing are discussed.     

Heritability estimates of spaced-plant traits in three perennial ryegrass (Lolium perenne L.) cultivars

Summary Seed yield in perennial ryegrass is low and unpredictable. Spaced-plant traits suitable for indirect selection for total seed yield in drilled plots would be very useful. The objectives of this investigation were to evaluate genetic variation for seed yield components and other traits among clones from three perennial ryegrass cultivars differing in seed yield and their open-pollinated progenies. Per cultivar, a random set of 50 genotypes was cloned and on each genotype seed was generated by open pollination. Clonal ramets of the parents were observed for 17 traits in 1986 at two locations. In 1987 and 1988, parents and progenies were observed as single plants in a randomized complete block design with two replications. There was little cultivar-environment interaction for most traits. The parents differed significantly for almost all traits. Half-sib (HS) families differed for only three to five traits. Broad-sense heritabilities (h² _b), based on variance components of the parents, were moderate to high; earliness had the highest h_b ². Narrow-sense heritabilities (h² _n), based on variance components among HS-families, were low to moderate and mostly not significant; for most traits h² _n estimates varied between years and cultivars. Flag leaf width and date of first anthesis showed the highest h² _n. Narrow-sense heritability estimates from parent-offspring regressions (h² _nPO) ranged from non-significant to high, depending on year and cultivar; they were generally higher than the corresponding h² _n estimates. Generally, h² _nPO was highest for earliness, flag leaf width, ear length and the number of spikelets per ear. Breeding methods that capitalize on additive genetic variance, such as mass selection, should result in improvement for these traits.     

Path and correlation analysis of perennial ryegrass (Lolium perenne L.) seed yield components

Maximum perennial ryegrass seed production potential is substantially greater than harvested yields with harvested yields representing only 20% of calculated potential. Similar to wheat, maize and other agriculturally important crops, seed yield is highly dependent on a number of interacting seed yield components. This research was performed to apply and describe path analysis of perennial ryegrass seed yield components in relation to harvested seed yields. Utilising extensive yield components which included subdividing reproductive inflorescences into five size categories, path analysis was undertaken assuming a unidirectional causal‐admissible relationship between seed yield components and harvested seed yield in six commercial seed production fields. Both spikelets per inflorescence and florets per spikelet had a significant (p < .05) direct effect on the overall seed yield; however, total path correlation coefficients showed that inflorescence size had the largest positive influence on seed yield via its indirect effects on other seed yield components. Our results will allow seed producers, seed production researchers and plant breeders alike to more efficiently increase harvested seed yield.     

贵州省贵草1号多花黑麦草种子生产技术规程

为了规范贵州省贵草1号多花黑麦草的生产,针对贵州省贵草1号多花黑麦草种子生产基地中的实际情况,依据国家、行业标准,对贵草1号多花黑麦草种子生产的环境条件、播种、田间管理和检验、收种、清选、贮藏等提出了具体要求和规定.该生产技术规程对贵州乃至西南诸省多花黑麦草种子的生产具有重要的现实指导意义.