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Perennial ryegrass is an important turf and forage grass in temperate regions worldwide. Limited genetic gains have been made with current breeding strategies compared with other grass crops, such as rice and maize, which benefit from Filial 1 (F1) hybrid breeding. One of the largest constraints on hybrid breeding in ryegrass is self‐incompatibility preventing inbreeding, as homozygous parental lines are required to develop hybrids with maximal hybrid vigour. Obligate outcrossing in ryegrass has resulted in cultivars with high levels of heterozygosity, lacking trait uniformity across the population. A naturally occurring self‐fertile (SF) locus that overcomes the self‐incompatibility system has been identified in a European perennial ryegrass population. This study crossed the SF locus into an elite cultivar, producing a self‐compatible population that was inbred for several generations. Genotyping‐by‐sequencing (GBS) was used to assess the population structure and degree of inbreeding in the self‐compatible population. Phenotypic analysis indicated that increased homozygosity did not necessarily affect growth and performance. This study concludes that self‐compatible ryegrass is a promising tool for hybrid breeding and agronomic improvement of perennial ryegrass. [ABSTRACT FROM AUTHOR]

A mutation causing self‐fertility (SF) in perennial ryegrass was studied at the tetraploid level. The aim of this work was to determine a) whether SF remains functional in a tetraploid population and b) whether the SF mutation expresses dominance in heterozygous pollen grains. A tetraploidized plant carrying SF alleles was self‐pollinated to create a segregating F2 population. In the F2 individuals, pollen compatibility ranged between 38% and 84% showing that SF remained functional. The SF locus genotype was the main determinant of pollen compatibility explaining 78% of the variation. The observed segregation was significantly different from the expected under both SF being dominant or recessive models (P(χ2)≤0.001) and tended to be intermediate between them, indicating partial dominance or additive gene action. The frequency of the different genotypes suggested that pollen grains homozygous for the mutation have a competitive advantage over heterozygous pollen and that pollen compatibility is affected by the interaction with additional loci. The implications of our results for breeding polyploid grasses are discussed. [ABSTRACT FROM AUTHOR]

Five candidate genes Lp IAA1, Lp RUB1, Lp BRI1, Lp SHOOT1 and Lp TB1 with putative function in plant architecture were allele sequenced in a panel of 96 diploid perennial ryegrass genotypes of diverse origin. The total length of the non-redundant genomic DNA alignment was 5425 bp and revealed 270 polymorphic sites in total. A negative significant Tajima's D value was detected in Lp TB1 gene, suggesting selection pressure for low-frequency alleles in this gene. All 96 genotypes were evaluated for plant height and dry matter yield over two years. Marker-trait associations were calculated between polymorphic sites and both phenotypic traits. Three indels and three single nucleotide substitutions in Lp TB1 gene were significantly (P < 0.05, q < 0.05) associated with plant height, while one indel was associated with dry matter yield. The results suggest putative role of Lp TB1 gene in plant height determination in perennial ryegrass and provide means for target allele selection. [ABSTRACT FROM AUTHOR]

Perennial ryegrass ( Lolium perenne L.) displays a two-locus gametophytic self-incompatibility ( SI) system that remains intact at the tetraploid level. Two models are plausible for SI in autotetraploids. In Model I: both alleles at the S locus and both at the Z locus in diploid pollen matching the female genotype results in incompatibility. In Model II: only one allele at S and one at Z locus in diploid pollen matching the female results in incompatibility. The goals were to determine which of the models best explains SI in our autotetraploid ryegrass population and to evaluate the efficiency of high-resolution melting ( HRM) genotyping for discriminating different iso-allelic genotypes. The progeny of a cross between two autotetraploids was characterized with three HRM-based markers co-segregating with Z. Segregation ratios were used to make inferences about the mode of action of the SI system. The observed segregation differed significantly (P < 0.001) from the expected under Model I, but not from the expected under Model II (P = 0.463). Thus, Model II explains SI in this population, and HRM is an efficient tool to distinguish different iso-allelic genotypic classes. [ABSTRACT FROM AUTHOR]

Proline is an important osmoprotectant in plant in response to osmotic stresses. Delta 1-pyrroline-5-carboxylate synthetase ( P5CS) is a key enzyme in proline biosynthesis. In this study, two P5CS genes ( PrP5CS1 and PrP5CS2) were isolated for the first time from perennial ryegrass. Expression analysis revealed that the transcript of PrP5CS1 in leaves was significantly up-regulated in two ryegrass cultivars exposed to 255 m m NaCl. The up-regulated level of PrP5CS1 was higher in salt-tolerant 'Overdrive' than in sensitive 'Pizzazz'. PrP5CS2 was significantly induced in 'Overdrive' but suppressed in 'Pizzazz' by NaCl treatment. In stems, however, there was no significant transcript change for both genes under salt treatment. The proline accumulation was significantly induced in both cultivars after salt treatment, and it was higher in 'Overdrive' than in 'Pizzazz' after 2 days of salt treatment. The results suggested that both genes are salt inducible and may be associated with salt-stress tolerance in perennial ryegrass. [ABSTRACT FROM AUTHOR]

Genomic selection ( GS) is a powerful method for exploitation of DNA sequence polymorphisms in breeding improvement, through the prediction of breeding values based on all markers distributed genome-wide. Forage grasses and legumes provide important targets for GS implementation, as many key traits are difficult or expensive to assess, and are measured late in the breeding cycle. Generic attributes of forage breeding programmes are described, along with status of genomic resources for a representative species group (ryegrasses). Two schemes for implementing GS in ryegrass breeding are described. The first requires relatively little modification of current schemes, but could lead to significant reductions in operating cost. The second scheme would allow two rounds of selection for key agronomic traits within a time period previously required for a single round, potentially leading to doubling of genetic gain rate, but requires a purpose-designed reference population. In both schemes, the limited extent of linkage disequilibrium ( LD), which is the major challenge for GS implementation in ryegrass breeding, is addressed. The strategies also incorporate recent advances in DNA sequencing technology to minimize costs. [ABSTRACT FROM AUTHOR]

With 1 figure and 1 table Abstract Perennial ryegrass is the principal forage grass species used in temperate agriculture. In recent years, significant efforts have been made to develop molecular marker strategies to allow cost-effective characterization of a large number of loci simultaneously. One such strategy involves using DArT markers, and a DArT array has recently been developed for the Lolium-Festuca complex. In this study, we report the first use of the DArTFest array to generate a genetic linkage map based on 326 markers in a Lolium perenne F2 population, consisting of 325 genotypes. For proof of concept, the map was used to identify QTL associated with differences in crown rust susceptibility, caused by the fungal biotroph, Puccinia coronata. [ABSTRACT FROM AUTHOR]

By using data of Belgian trials for Value of Cultivation and Use (1963–2007) the change in agronomic performance of ryegrass varieties was quantified. Data included 144 Lolium perenne and 69 Lolium multiflorum candidate varieties, plus ‘Vigor’ and ‘Lemtal’, two varieties which were always included in the Value of Cultivation and Use (VCU) trials. As the genetics of ‘Vigor’ and ‘Lemtal’ have remained identical to those in 1963, these were used as constant standards to measure improvements of new varieties. Dry matter yield (DMY) of ‘Vigor’ and ‘Lemtal’ varied annually but did not show a progressive change, indicating that cultural changes in VCU trials of ryegrasses were small. By expressing DMY, persistency and rust resistance of the candidate varieties relative to Vigor and ‘Lemtal’, the change in agronomic performance due to breeding was determined. DMY increased with 0.3% of ‘Vigor’ and ‘Lemtal’ annually. Persistency showed an annual increase around 0.5% of the standard varieties. Before 1990, rust resistance of ryegrasses varied around 100% relative to ‘Vigor’ or ‘Lemtal’. After 1990, an annual increase of 3.6% against these standard varieties was found. [ABSTRACT FROM AUTHOR]

The objective of this study was to map resistance gene analogues (RGA) and quantitative trait loci (QTL) for powdery mildew resistance in perennial ryegrass ( Lolium perenne L.). The mapping population consisted of 184 F2 genotypes produced from a cross between one genotype of a synthetic perennial ryegrass variety Veyo and one genotype from the perennial ryegrass ecotype Falster. The greenhouse infection was measured as number of sporulating colonies on a 10-cm leaf area with the maximum possible number of colonies to be counted set to 50. The range of infection scores in the population was 0–50 and the heritability was 71.7%. In total, two QTL for powdery mildew resistance were identified, and mapped to linkage groups (LG) LG3 and LG7. Individually, these QTL explained between 7.5% and 22.1% of the total phenotypic variation. Six RGA and three laccases were mapped to LG2, LG3, LG4, LG5 and LG7, however, no close linkage between RGA and QTL was observed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Crown rust is an economically devastating disease of perennial ryegrass. Both artificial crown rust inoculations, with the possibility of several selection cycles in one year, as well as marker-assisted selection can be used for more efficient breeding of new resistant cultivars. The objective of this study was to map quantitative trait loci (QTL) for response to crown rust infection in perennial ryegrass. In order to identify relevant markers for response to crown rust infection, QTL mapping was performed on a ryegrass mapping population which was evaluated for resistance in the field for two years as well as by artificial pathogen inoculations using a detached leaf assessment. The broad sense heritability values for the field, detached leaf and combined assays were 0.42, 0.56, and 0.64, respectively, indicating a good potential for selection for crown rust resistance. A total of six QTLs were identified and mapped to linkage groups (LG) LG1, LG4 and LG5, explaining between 6.8% and 16.4% of the total phenotypic variation. [ABSTRACT FROM AUTHOR]

Bacterial wilt caused by Xanthomonas translucens pv. graminis ( Xtg) may lead to severe damage and substantial yield losses in Italian ryegrass, Lolium multiflorum Lam. To identify candidate genes for marker-assisted breeding and to investigate the molecular basis of the host-pathogen interaction, this study focused on searching the ryegrass genome for resistance genes and key signal transduction elements in the defence response. cDNA-amplified fragment length polymorphism (AFLP) was used to analyse differentially expressed genes at six time-points after infection in a partially resistant genotype of L. multiflorum infected with Xtg. A total of 87 selective primer combinations resulted in 173 differentially expressed transcript-derived fragments (TDF) out of which 37 TDFs were isolated. Database searches revealed sequence homologies of various TDFs to sequences such as ERBP-transcription factors, an TGF- β receptor interacting protein, a terpene synthase and various other genes expressed in response to bacterial and fungal infection. Reverse transcription-polymerase chain reaction (RT-PCR) and quantitative RT-PCR (qRT-PCR) confirmed the expression patterns found by cDNA-AFLP. The TDFs identified represent candidate genes for the identification of quantitative trait loci (QTLs) involved in resistance to bacterial wilt. These TDFs may also allow for the identification and analysis of avirulence genes expressed by Xtg. The results of this study provide a valuable basis not only for a better understanding of the genetic control of resistance to bacterial wilt in Italian ryegrass, but primarily for the development of molecular tools to improve resistance breeding. [ABSTRACT FROM AUTHOR]

Genomic in situ hybridization (GISH) was used to characterize the chromosome constitutions of individual plants from a set of tetraploid and hexaploid cultivars of Festulolium developed and released in the Czech Republic from hybrids of Lolium multiflorum with Festuca pratensis and F. arundinacea. A simplified GISH protocol readily discriminated parental genomes in the hybrids and facilitated the screening of large numbers of plants per accession. The contribution of parental genomes in the cultivars tested ranged from predominance of chromatin from one of the parents to a more balanced contribution from both parents. However, in none of the cultivars were equal proportions of chromatin from both parents present. The parental contribution to the hybrids was both in the form of complete chromosomes or as chromosome translocations. In hexaploid cultivars from ( L. multiflorum × F. arundinacea) × F. arundinacea hybrids the average numbers of complete L. multiflorum chromosomes ranged from 4.95 to 7.5 and the numbers of translocations from 6.33 to 10.21. Two tetraploid cultivars from ( L. multiflorum × F. arundinacea) × L. multiflorum hybrids showed a strong prevalence of L. multiflorum chromatin and intergeneric translocations were rare. In the tetraploid cultivar ‘Perun’ of the L. multiflorum × F. pratensis hybrid there were 11.7 chromosomes of L. multiflorum and 14.7 recombined chromosomes on average. Reasons for the domination of one of the parental genomes in hybrid cultivars are not clear and are only partially explained by breeding history. Recombination rates of individual genomes in hybrids involving F. arundinacea were evaluated in double hybridization experiments. The results indicated a strong affinity of the L. multiflorum genome for the F. pratensis genome present in F. arundinacea and little affinity for the F. glaucescens genome. This suggests that introgressions from F. arundinacea into L. multiflorum are primarily limited to the F. pratensis genome which can be more readily accessed in L. multiflorum × F. pratensis hybrids. [ABSTRACT FROM AUTHOR]

Perennial ryegrass (Lolium perenneL.) is the most important grass species for temperate grassland agriculture. The genetic relationship and distance among cultivars is largely unknown but of great interest for breeding programmes. The objectives of this study were to (i) investigate the molecular variation and structure of population cultivars, (ii) describe the relationship among cultivars in terms of the modified Rogers’ distance, and (iii) determine the minimum sample size required for characterization of cultivars ofL. perenneusing random amplified polymorphic DNA (RAPD) markers. A total of 22 ryegrass cultivars, mainly of European origin, were investigated with RAPD markers. The minimum sample size required for the characterization of cultivars was about 20 individuals per population. An analysis of molecular variance (amova) revealed a much larger genetic variation within cultivars (66%) than between them (34%). [ABSTRACT FROM AUTHOR]

Perennial ryegrass (Lolium perenneL.) is the most important temperate forage grass species. Unfortunately, the nutritional value of perennial ryegrass declines as maturity progresses, mainly because of a high concentration of poorly digestible compounds in inflorescences. Therefore, the development of forage-type ryegrass varieties with extended vegetative growth is of interest for agriculture. To delay floral transition in perennial ryegrass theArabidopsis ATH1gene driven by the maize ubiquitin promoter, the rice actin promoter or the rice OSH1 promoter, respectively was introduced. InATH1-expressing plants heading was delayed, and in a number of cases the plants never flowered at all. Such non- or late-heading was accompanied by the outgrowth of normally quiescent lateral meristems into extra leaves, resulting in a leafy growth habit. When eventually heading, these plants generally produced a reduced number of inflorescences. These observations suggest thatATH1-mediated delay of heading may be useful to improve fodder quality of perennial ryegrass. [ABSTRACT FROM AUTHOR]

Molecular diversity and genetic affinity in the Lolium/ Festuca grass complex have been assessed using simple sequence repeat (SSR) marker technology. The genotypic set was derived from three accessions of perennial ryegrass, two cultivars of Italian ryegrass, two cultivars of meadow fescue, two cultivars of tall fescue and 10 accessions from different intergeneric hybrid ( Festulolium) combinations. The majority of the genomic DNA-derived SSR primer pairs from perennial ryegrass (LPSSR) and Italian ryegrass (LMSSR) produced clear, simple and distinctive amplification products from the majority of the genotypes. The efficiency of cross-specific amplification for LPSSR markers varied from 38% in meadow fescue to 93% in two cultivars of Festulolium and from 57% in meadow fescue to 87% in Italian ryegrass for LMSSR markers. Of 40 amplified markers, 14 (35%) produced species-difference alleles in the relation to cultivars used in the present study. Thirty-five LPSSR locus-derived alleles were found to be specific to Lolium species, four to meadow fescue and six to tall fescue. For LMSSR alleles, eight were specific to Lolium species and five were only associated with Italian ryegrass, and null alleles were detected for meadow fescue in all instances. These species-difference markers could clearly identify different accessions of Festulolium. Cluster analysis separated the individual taxa and showed grouping of intergeneric hybrids based on genomic composition. The data distinguished between the species and reflected the known pedigree of the cultivars and the differences between the species. The dendrogram also distinguished between the Festulolium accessions and clearly demonstrated the relations between Festulolium hybrids and their parent species. [ABSTRACT FROM AUTHOR]

Abstract Linkage maps of perennial ryegrass were constructed from F2 and BC1 -type populations using, predominantly, restriction fragment length polymorphism data based on heterologous probes used in mapping other grass species. The maps identified seven linkage groups, which covered a total of 515 cM (F2 ) and 565 cM (BC1 ). They were aligned using 38 loci identified in both populations (common loci) and a possible marker order for all mapped loci in either population was identified in an integrated map. The estimated recombination frequencies and map distances between adjacent common loci were compared between the two data sets and regions of heterogeneity identified. Overall, the common markers identified a map distance of 446 cM in the F2 population and 327 cM in the BC1 population, reflecting a higher recombination frequency in the former, although the difference was not evenly spread over the seven linkage groups. [ABSTRACT FROM AUTHOR]

Abstract Selection of main cool-season turfgrasses (perennial ryegrass and red fescue) for resistance to red thread disease caused by Laetisaria fuciformis has not progressed during the last 30 years because of low reproducibility of experiments carried out under natural infection. In this study, evaluation of a set of the turfgrass cultivars, including non-host fodder grasses as control, was performed in a climatic chamber, a cold house and in the field using three types of artificial inoculum, and correlations between trials were analysed. In general, cultivars of Festuca rubra were more susceptible to the disease but differentiated better than cultivars of Lolium perenne . Significant interactions between cultivars of L. perenne and F. rubra and isolates of L. fuciformis were found. The fungus was also able to colonize leaves of sow thistle and wheat seedlings. In field conditions and in the glass cold-house Dactylis glomerata was found to be relatively resistant to red thread disease. A possible selection programme is proposed. [ABSTRACT FROM AUTHOR]

Crown rust, Puccinia coronata Corda, causes one of the most damaging foliar diseases in Italian ryegrass, Lolium multiflorum Lam. For introgression of crown rust resistance, highly resistant hybrids of the crosses Festuca arundinacea (2n = 6x = 42) × L. multiflorum (2n = 4x = 28) and reciprocally, L. multiflorum (2n = 2x = 14) × Festuca pratensis (2n = 4x = 28) and subsequently resistant recombinant individuals were used as female parents and susceptible cultivars of Italian ryegrass as male parents in three successive backcrosses. The BC[sub 3] plants were selfed and crossed mutually. Uredospores of seven different crown rust isolates collected from plants of L. multiflorum, Lolium perenne, F. pratensis, F. arundinacea and L. multiflorum × F. pratensis hybrids were applied to identify the resistance or susceptibility of the parental species, backcrossed, selfed and intercrossed progenies. The various crown rust populations revealed a species-specific capability to infect plants of the Lolium–Festuca complex corresponding to the host species from which the spores originated. Selected BC[sub 3] plants, however, were found to be completely resistant to all crown rust populations tested. Successful introgression of the resistance was achieved from F. arundinacea as well as from F. pratensis. The resistance represents a dominant character, apparently based on a strong heterologous incompatibility between host and pathogen. In phenotype, bivalent formation during meiosis and in fertility, the novel germplasms are comparable with the L. multiflorum cultivars. [ABSTRACT FROM AUTHOR]

To assess the usefulness of the doubled haploid (DH) method in the breeding of forage grasses, a sample of anther-derived progeny of penta-ploid F[sub1] hybrids of Festuca arundinacea × Lolium multifiorum was karyotyped using genomic in situ hybridization (GISH). The technique allowed scoring of the total number of chromosomes, the number of chromosomes contributed by each parent, and the number and positions of the Festuca-Lolium translocation breakpoints. Among 27 plants analysed, 13 belonged to three clones, effectively reducing the number of different progeny karyotyped to 17. These included 10 haploids, five doubled haploids and two plants for which the origins could not be explained. In all plants analysed, a mixture of chromosomes of both parents was present, including an average of 1.88 intergeneric translocations per plant. The translocation breakpoints were distributed along almost the entire length of the chromosome arms Chromosome variation among androgenic progeny appeared much wider than that in the conventional backcross but low vigour and high mortality suggest that this additional variation may be difficult to exploit directly in breeding However, a change in the pattern of recombination makes the entire genotne accessible to manipulation [ABSTRACT FROM AUTHOR]

A genetic map of Lolium has been produced using isozyme, restriction fragment length polymorphism (RFLP) and random amplified poiymorphic DNA (RAPD) markers applied to a segregating family derived from an F[sub1] hybrid plant of L. perenne × L. multiflorum provenance, crossed on to a doubled haploid L. perenne A total of 106 markers, out of a total of 160 polymorphic loci analysed, have been ascribed to seven linkage groups covering a map distance of 692 CM. Two of these groups may be allocated to chromosomes 2 and 6 of the Loliurn genome. The remaining unallocated markers, the majority of which showed severe segregation distortion, could be associated into small groups of two or three markers which showed no linkage with the main groups at a LOD of 24.8 or, if associated, could not be mapped in a satisfactory manner. This high incidence of disturbed segregations could be accounted for by the use of an interspecific hybrid between two species of differing genome size, with consequent cytological imbalance. [ABSTRACT FROM AUTHOR]

Improving rust resistance is one of the main goals in our breeding programme with perennial ryegrasses. We have studied the behaviour of our breeding material over several years in several locations under natural and artificial infection conditions. The narrow sense heritability of crown rust resistance is fairly high (0.46), providing scope for improving resistance, but this optimism is reduced by the negative correlation with yield. The most resistant material yielded 4% less than the most susceptible material. No decline in digestibility is expected when improving the disease resistance. The incidence of crown rust is very variable between years, locations and between spontaneous and artificial infections, creating constraints in selection. Observations for several years and at several locations appear to be the best way to improve rust resistance in perennial ryegrass. [ABSTRACT FROM AUTHOR]

This paper reports on the first results of feeding value experiments, assessed with sheep, of hybrids between tetraploid Italian ryegrass (Lolium multiflorum, 2n = 4x = 28) and a progenitor of tall fescue, Festuca arundinacea var. glaucescens (2n = 4x = 28). Three hybrid populations resulting from either high, low or no selection for palatability were compared with a variety of Italian ryegrass as control and two varieties of the cultivated hexaploid (2n = 6x = 42) tall fescue, one of which had been selected for high palatability. On average, the hybrid populations were found to be as palatable as the improved tall fescue with voluntary intake (VI), in vivo digestibility of organic matter (DOM), and net energy expressed in fodder units for milk, similar to the best palatable tall fescue and to Italian ryegrass. However, selection for improved palatability among hybrids did not result in any further improvement of other traits, except VI in the hybrid selected for high palatability which significantly exceeded VI of Italian ryegrass. In conclusion, intergeneric hybridization between L. multiflorum and F. arundinacea var. glaucescens led to an immediate increase of feeding value compared with selection for palatability in tall fescue. However, to improve feeding value of hybrids further, similar selection for high palatability appeared questionable and possibly detrimental for other agronomic traits because of complicated inheritance in tetraploid L. multiflorum × F. glaucescens hybrids. [ABSTRACT FROM AUTHOR]

In the Mediterranean environment, root systems are very important for water utilization. For this reason, the effects of selection for increased root dimensions upon root and shoot characteristics of a natural population of Lolium rigidum Gaud. were analysed. Two cycles of phenotypic recurrent selection were carried out on a population collected in Nurra (north-western Sardinia, Italy). Plants derived after two cycles of selection, together with unselected plants, were grown hydroponically in a greenhouse. Data on root volume, longest root length, number of stems and leaves, leaf length, shoot and root dry weight were collected from the selected material and also from unselected material for use as a control. An analysis of variance was performed and correlation coefficients were calculated. The increased size of the root system did not have a negative effect on the above-ground biomass and there was genetic variation for root traits in the 'Nurra' population. The improved population will be utilized for further breeding work to obtain L. rigidum varieties capable of withstanding dry periods during the vegetative phase. [ABSTRACT FROM AUTHOR]

Five broad-based breeding populations were produced by polycrossing natural populations sampled in five clusters developed by a hierarchical method with a geographic-contiguity constraint. As a result, each of these breeding populations originates from a single region and the populations within a cluster are more likely to share the same alleles with similar frequencies. A single generation of intercrossing would therefore be sufficient to establish a panmixia equilibrium. These populations were tested for dry-matter yield in plots and compared to control cultivars in two locations. There were some trends of specific adaptation related to the geographic origin of populations, which, on average, compared well to controls. Their half-sib families were evaluated as spaced plants in one location. This allowed genetic parameters and expected response to selection to be computed. Three out of five breeding populations appeared to be promising for the development of new. improved synthetic varieties. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In order to study the effects of competition on the genotypic composition of chance-hybrids in Lolium multiflorum, eight chance-hybrids were produced according to Burton (1948). inbred lines and cultivars were used as parents. The proportions of parental and hybrid components in the seeds and growing-field stands of the chance-hybrids were determined over three cuts using gel electrophoresis The realized hybrid proportions in the seeds, at a maximum of 38.3%, were considerably lower than the theoretically expected 50%. In the field stands, the hybrid proportions of the chance-hybrids derived from inbred lines increased considerably and continously over cuts, whereas those of the chance-hybrids produced from cultivars increased only slightly. A maximum hybrid tiller proportion of 76.8% was found at the third cut. Correspondingly. the total yield of the chance-hybrids produced from cultivars was only slightly higher than that of the parents The production of chance-hybrids, therefore, proved to be sensible only if inbred lines had been used as parents. [ABSTRACT FROM AUTHOR]

A defined method for the rapid establishment of cell suspensions releasing small-cell colonies and their regeneration to fertile plants is described Cell suspensions were obtained from 10 mature, lengthwise-divided embryos Five of the 10 suspensions regenerated green plants. Filtration of suspensions through a 150 μm mesh followed by generation was carried out 28 days after initiation of the suspensions, to demonstrate a rapid release of regeneration small cell colonies from cell suspensions using the protocol described. Two of the 10 filtered suspensions regenerated green plants from small cell colonies. [ABSTRACT FROM AUTHOR]

Seed production in perennial ryegrass, Lolium perenne L., is low. Early selection for high seed yield carried out in spaced plants would be valuable for breeders, but only if this potential is also expressed in derived progenies sown later in drilled plots. Therefore, spaced-plant traits assessed on clonal ramets of 31 genotypes in each of two perennial ryegrass varieties in four environments were related to seed production characteristics in drilled plots of open-pollinated progenies of these plants. Significant differences were found among these half-sib families for seed yield, thousand-grain weight, spring performance and earliness. The number of spikelets per ear in the maternal plants was negatively correlated with the seed yield of the progenies, explaining 17 % of the variation for seed yield in the cv. 'Barenza' and 14 % in the cv. 'Wendy'. Multiple regression analyses revealed that no combinations of plant traits consistently explained a major portion of the variation for seed yield of the progenies. The results indicate that in these varieties, spaced-plant data are of limited value in predicting seed production. Direct selection for seed yield in drills of progenies in later stages of the breeding programme remains the best method for obtaining varieties with sufficient seed production. [ABSTRACT FROM AUTHOR]

In order to establish an appropriate breeding programme, the reproductive system of a population of Lolisium rigidum Gaud. from Sardinia was analyzed to determine the mechanisms operational in this species. A dual approach was adopted of genotype assay, exploiting the polymorphism at the PGI-2 locus, and an assessment of the effects of inbreeding on agronomic characters. The statistical analysis showed highly significant differences for the number of plants due to selfing among the 35 progenies obtained by controlled crossing of genotypes homozygous for different alleles at the PGI-2 locus. The greatest inbreeding effect was on dry matter yield. Although at a bulk population level the species is outbreeding, highly self-compatible plants can be found within this naturally-derived population. [ABSTRACT FROM AUTHOR]

The in parameters, variances, covariances and heritabilities, caused by the Bulmer effect have been predicted for an artificial breeding population of perennial ryegrass using recursion formulae. This enabled anticipation of the decrease in the expected response to multitrait index selection, using two different sets of economic weights. This theoretical decrease in selection efficiency was found to be quite substantial; it is approximately halved after 4 cycles of individual recurrent selection with a fairly high selection intensity of 5 %. However the synthetic population is improved for 4 out of 5 agronomic traits and could theoretically reach quite a high level of performance after 5 cycles. The choice of economic weights has relatively little influence on the expected genetic progress of each trait. [ABSTRACT FROM AUTHOR]

In a back-crossing programme involving Lolium multiflorum (the recurrent parent) and Festuca arundinacea, the diploid L. multiflorum phenotype was rapidly recovered with the inclusion, in some progeny, of a small number of genes from the fescue parent. In field drought trials derivatives of these backcross populations were on average less drought resistant than the L. multiflorum parental populations, but 3 % of individuals were as drought resistant as F. arundinacea. After only one cycle of selection and polycrossing these drought-resistant Lolium-like plants, the mean drought resistance of most progeny lines was significantly improved, in some cases to near that of F. arundinacea. Available evidence strongly indicates that this improved drought resistance was due to the transfer of genetic material from Festuca into Lolium. These populations will contribute to variety improvement and to our understanding of the genetics and physiology of drought resistance. [ABSTRACT FROM AUTHOR]

Analysis of a half diallel cross among four white clover cultivars, grown as monocultures and in mixtures (duocultures) with two separate perennial ryegrass cultivars, confirmed that for stolon and leaf number a higher proportion of the genetic variance in duocultures was non-additive. For canopy height and dry weight, however, this proportion was less affected by inter-specific competition. An additive-dominance model of gene action sufficed for all four characters in monocultures, but in duocultures epistasis was just one of the factors complicating the genetic picture. This, coupled with short-term reversals in the direction of dominance, merely illustrates the complexity of breeding white clover cultivars, Possible future developments in the breeding of white clover are discussed in the light of these results. [ABSTRACT FROM AUTHOR]

The objective of the study was to determine the effect of selection for large root dimension on root and shoot characteristics of an Italian variety of Lolium perenne L. (cv. ‘Vejo’). Two cycles of recurrent restricted phenotypic selection (RRPS) were carried out in 1983 and 1984 at Perugia (Italy). In each cycle, 20 out of 1,500 plants were selected and intercrossed under isolation. In 1985, 120 plants from ‘Vejo selected’ and an equal number of plants from ‘Vejo’ initial seed-lot were grown hydroponically for 92 days; at the end of the experiment, the plants were measured for their number of leaves and stems, leaf length, length of the longest root, root volume and shoot and root dry weight. Sufficient genetic variability existed among plants of cv. ‘Vejo’ to allow highly significant responses to selection for root dimension (+ 2i % in root length, +39 % in root volume, 4-67 % in root dry weight and + 3 1 % in root: shoot dry weight ratio). Furthermore, two cycles of RRPS for root dimension did not show negative responses of the aboveground parts of the plant. [ABSTRACT FROM AUTHOR]

Anther-culture response in Lolium perenne was studied in the hybrid populations horn three responsive diploid parent clones to obtain genotypes with superior another-culture response through hybridization. Genetic variation for another-culture response was significant both within and between the four hybrid families and their parents. A reciprocal effect was indicated for embryo formation and regeneration non percentages for one of the cross combinations. Among 55 hybrid clones tested in two environments, 6 clones were identified with an anther- culture response level superior to their parents. While the parents produced one green plant or less per 100 anthers, these superior clones produced from 11 to 59 green plants/100 anthers, mainly as the result of improved embryo formation and improved percentages of regenerated plants being green. A significant correlation (r = 0.397**) was observed between embryo formation and percentage of green plants. The results are discussed with regard to the possible transfer of anther-culture response to non-responsive breeding material through hybridization. [ABSTRACT FROM AUTHOR]

The suitability of different protocols was compared for entire plant regeneration by somatic embryo-genesis, of the forage plants Lolium multiflorum Lam. (Italian ryegrass) and Festuca arundinacea Schreb. (tall fescue). In the first protocol, immature embryos were used as starting material, while mature seeds were retained in the other two. Whichever the considered protocol, undifferentiated calli were produced on MURASHIGE and SKOOG MS medium supplemented with 2,4-D. The calli were subcultured in the dark on solid MS agar medium, containing 5 mg/l 2,4-D (protocol 2) or on solid MS medium followed by transfer to a rotated liquid MS medium with 2 mg/I 2,4-D (protocol 1). In these conditions, induction of somatic embryogenesis occurred, and whole plants were regenerated during a limited lapse of time, upon transfer in the light, to MS medium supplemented with BAP but devoid of 2,4-D. The simultaneous elimination of 2,4-D and transfer to light appeared essential for full regeneration of the plants. Using this characteristic, an additional step was added to a new protocol (protocol 3) in which microcalli, cultured on liquid MS medium containing 5 mg/l 2,4-D, were transferred to the same medium with 2 mg/l 2,4-D, in the dark. In these conditions, the suspensions kept their embryogenic potential for months. In all cases, plantlets were successfully transferred into the soil. An evaluation of the somaclonal variation potential of the plants issued from each protocol is now underway. [ABSTRACT FROM AUTHOR]

The investigation was carried out to obtain double haploid homozygous lines of Lolium. Lolium multiflorum ssp. gaudini cv. 'Liwelo', 44 clones and five different cultivars (cv.) of L. perenne were tested with regard to their anther culture response on a solid medium. Callus production and plant regeneration of the different genotypes were investigated. Within L. m. ssp. gaudini green plants have been obtained. In L. perenne significant genotypical differences in the in vitro reaction could be demonstrated. A high-responding genotype was selected which produced a maximum of 20 % green plants. A variety × temperature interaction was found for the L. perenne varieties 'Premier' and 'Barlenna'. The production of 34 green plants out of eight clones enables a first analysis to be made of the inheritance of Barley Yellow Dwarf Virus resistance in L. perenne. [ABSTRACT FROM AUTHOR]

From 22 genotypes, selfed (S1) and testcross progenies were investigated. The latter were generated by i) polycross (PX) and ii) 2 topcrosses (TC) using cms-inbred lines as a tester. Progenies were tested for annual dry matter yield in 3 successive years, the 3-year average was 76.7 dt/ha for S2 and 76.9, 80.1 and 74.5 for PX, TC 1 and TC 2, respectively. Genetic variance was highest for S11 (20.42), while the average of the 3 testcrosses was 12.22. However, the genotype-year interaction variance of S: Was 52.21, being 2--3 times greater than for the 2 topcrosses. PX progenies were the most stable across years. Predicted response to selection was highest for S1 (10.4 %). Genetic correlation (rg) between S1 and the testcrosses was highest with TC 2 (rg = 0.593+ +). [ABSTRACT FROM AUTHOR]

From 28 genotypes, half-sib families were generated by polycross (PX) and 2 topcrosses (TC). TC-testers were partially inbred cms-lines. Progenies were tested for annual dry matter yield in 3 successive years. The three year average was 80.7, 76.6 and 74.0 dt/ha for TC 1, PX and TC 2, respectively. TC 1 had the highest yielding families and the largest mean in all years. TC 2 revealed the largest range among its families. Genetic variance was highest for TC 2 with 14.02, followed by TC 1 and PX with 12.05 and 10.92. However, genotype × year interaction variance was about 2 and 4 times greater for TC 1 and TC 2 as compared to PX. Genetic correlation between testcross progenies was tightest for PX vs. TC 1 (rg = 0.644++ ), while between the two TC's only rg = 0.307+ was observed. Predicted response to selection yielded very similar results for all test-crosses. [ABSTRACT FROM AUTHOR]

A Triple Test Cross and basic generations (i.e. inbred parents, F1's, F2's and backcrosses) have been used to investigate the generics of dry matter yield in a population of Lolium perenne. Two trial designs, short, individual plant drills and larger sown plots were used at each of two sites iii the U.K., at Aberystwyth and Birmingham. The families studied correspond to those raised as spaced plants and reported in the first paper in this series. In contrast to the spaced plants trial, the drill trial resulted in considerable epistasis as well as additivity and dominance variation whilst the plot trial failed to identify any significant genetic variation. There "as considerable G × E interaction over sites and harvests, particularly in the amount of dominance. The latter showed a clear linear relationship with mean per- formance at both sites, the dominance ratio being higher in the poorest environments. This is largely due to the additive variance decreasing in the poor environments rather than the dominance being higher. The implications of these results to grass breeding are discussed. [ABSTRACT FROM AUTHOR]

The meiotic behaviour of the hybrid between Festuca gigantea (2n - 6x = 42) and Festuca arundinacea (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 combines 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 autotetraploic L. multiflorum × F. gigantea is sufficiently fertile to be used as the pollen plant in crosses with diploid L. multiflorum (BC[Sub1]. Backcrossing the BC[Sub1] 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 of combining specific complementary characters of the two species. [ABSTRACT FROM AUTHOR]

A diallel cross amongst four contrasting white clover varieties was used provide genetic information on those characters which affect the productivity of white clover-perennial ryegrass mixtures when grown under a cutting-only management regime. Generally speaking those characters recorded on the clover families and in mixtures exhibited highly significant additive and non-additive genetic effects, though for some characters the latter could not be ascribed solely to dominance effects. For two of the clover characters, stolon and leaf number, the generic picture was radically altered in mixtures by the effects of inter specific competition. Pseudogeneric effects were also detected for the grass characters, but it was suggested that the two ryegrass varieties used here were exhibiting phenotypic plasticity. As a group the tour intra-varietal crosses performed significantly better than the six inter-varietal crosses for all clover and mixture characters. Only one of the inter-varietal crosses had significantly positive specific combining ability effects or most characters and that was between the two long established varieties "S. 184" and "S. 100." The implications of these results for the breeding of white clover varieties for use in mixtures are briefly discussed. [ABSTRACT FROM AUTHOR]

A diallel crossing programme amongst four contrasting white clover varieties was used to generate material for studying the interrelationships amongst those characters which affect the productivity of white clover-perennial ryegrass mixtures under a cutting-only management regime. Such a regime favoured clover growth. All the clover characters exhibited strong positive correlations with mixture yield. However, this combination of clover characters did nor promote growth of the grass companion. For this a low growing variety with a dense stolon network appeared preferable. Path analysis indicated that differences existed between the two companion grass varieties used for this experiment in their effects upon clover characters. [ABSTRACT FROM AUTHOR]

Components of seed yield were estimated for each set of 100 plants derived from six varieties of Lolium perenne. Significant differences between the varieties were found for all components of seed yield, but the range was broader within each variety. An indirect selection of seed yield using the character seeds per spike produced a selection response similar to that obtained by direct selection on high seed yield per plant. A direct and indirect selection of characters estimated in small, drilled plots of topcross off- springs (F1) was less successful than the selection based on the single plants. Spearman rank correlation coefficients between the single plants and their offsprings did not show significant agreement for seed yield. But altogether the results indicated that the increase of seed yield/area was about 6 % when 10 % of the best plants were selected. [ABSTRACT FROM AUTHOR]

Development of tall rescue (Festuca arundinacea Schreb., 2n = 6x = 42) x Italian ryegrass (Lolium multiflorum Lam., 2n = 2x = 14) hybrids would enhance efforts to improve the quality of tail fescue. Two 'Kentucky 31' tail rescue χ 'Lemtal' Italian ryegrass hybrids were obtained via embryo rescue on MS media containing casein hydrolysate, ascorbic acid and sucrose. Chromosome pairing at metaphase I had an average of more than 12 bivalents per cell. Since festuca-Lolium pairing can account only for seven of the paired chromosomes. intergenomic as well as interspecific chromosome pairing is indicated. There was no cytoplasmic effect on chromosome pairing. To determine if enzymes could be used as genetic markers for distinguishing hybrids from self-contaminants in crosses, zymograms of PGI, 6-PGD, MDH, GOT and ACPH were obtained from parents and hybrids using starch gel electrophoresis. PGI, 6-PGD and MDH had fewer bands in the diploid ryegrass, as compared with the hexaploid tall rescue and the tetraploid hybrid. [ABSTRACT FROM AUTHOR]

Fifty-three genotypes of perennial ryegrass selected from a range of cultivars and ecotypes were evaluated for their reaction to crown rust isolates collected from Western Australia, Victoria, Queensland, South Australia or New South Wales in Australia. The reactions of the clones to inoculation provided evidence for the development of a differential set of perennial ryegrass genotypes, but also demonstrated that a large number of genotypes displayed universal reactions to infection with any of the crown rust isolates. [ABSTRACT FROM AUTHOR]

To predict any genetic response to selection, two breeding populations of perennial ryegrass, consisting of half-sib families, were evaluated as spaced plants from 1987 to 1989 for several agronomical traits. In each population, the best plants selected through a multitrait Smith and Hazel's index were planted in a polycross to produce the second generation half-sib families. Both generations were evaluated together from 1991 to 1993 as spaced plants. The difference between generations was the observed genetic response, which was compared to that predicted. Rust tolerance, aftermath heading and persistence were significantly improved in both populations. In trial plots used to assess the yield, no effect of mass selection was noticed. Thus it is concluded that mass selection failed to increase productivity but produced some improvements in disease tolerance and aftermath heading. [ABSTRACT FROM AUTHOR]

The genetic basis for crown rust resistance was analysed in the progeny of reciprocal crosses between Lolium multiflorum plants that were either resistant (cv. ‘Axis’) or susceptible to crown rust. The progeny harvested from the resistant parent was two- to seven-fold more resistant than the progeny harvested from the susceptible parent. These data indicate the presence of a maternal factor which increases resistance to crown rust in some of the ryegrass plants used as parents. [ABSTRACT FROM AUTHOR]

An improved method is reported for polyploid induction in Lolium (ryegrass), and in sterile F1 hybrids between Lolium and Festuca (fescue). Two factors greatly increased the survival rate of colchicine-treated embryos of Lolium perenne (perennial ryegrass) germinated and cultured in vitro: (1) a high concentration of sucrose (100 g/l) in the germination medium and (2), maintenance at a low temperature of 10°C for 2 weeks after treatment. The maximum success rate for chromosome doubling among survivors of perennial ryegrass was 79.1%, and for L. perenne × Festuca arundinacea F1 hybrid embryos it exceeded 40%. The same doubling treatment also works with shoot tip culture in non-flowering genotypes obtained by anther culture of L. multiflorum × F. arundinacea hybrids. [ABSTRACT FROM AUTHOR]

New opportunities for plant breeding using androgenesis in Lolium × Festuca hybrids have been identified. Plants derived by anther culture from a Lolium multiflorum × Festuca arundinacea (5x) hybrid were screened for freezing-tolerance, and their post-freezing recovery compared. The androgenic population showed extreme diversity in freezing-tolerance. While the majority of androgenic plants had inferior freezing-tolerance compared with the freezing-sensitive L. multiflorum parent, 6% of the population were more freezing resistant than the freezing-tolerant Festuca parent. Novel Lolium and Festuca gene combinations resulting from rare meiotic events were recovered within the androgenic population. The two most freezing-tolerant androgenic plants carried virtually the entire F. pratensis subgenome of F. arundinacea. F. pratensis is known to carry genes for freezing-tolerance and would be expected to be the primary source of genes governing this trait within the F. arundinacea genome. The most freezing-tolerant androgenic plants were more freezing-tolerant than the hybrid plant from which they were derived. Consequently, androgenesis was also effective in removing factor(s) reducing the expression of freezing-tolerance within the L. multiflorum × F. arundinacea (5x) hybrid. [ABSTRACT FROM AUTHOR]