Marc Ghesquière

Complementary effects of species and genetic diversity on productivity and stability of sown grasslands.

Plant species diversity regulates the productivity1–3 and stability2,4 of natural ecosystems, along with their resilience to disturbance5,6. The influence of species diversity on the productivity of agronomic systems is less clear7–10. Plant genetic diversity is also suspected to influence ecosystem function3,11–14, although empirical evidence is scarce. Given the large range of genotypes that can be generated per species through artificial selection, genetic diversity is a potentially important leverage of productivity in cultivated systems. Here we assess the effect of species and genetic diversity on the production and sustainable supply of livestock fodder in sown grasslands, comprising single and multispecies assemblages characterized by different levels of genetic diversity, exposed to drought and non-drought conditions. Multispecies assemblages proved more productive than monocultures when subject to drought, regardless of the number of genotypes per species present. Conversely, the temporal stability of production increased only with the number of genotypes present under both drought and non-drought conditions, and was unaffected by the number of species. We conclude that taxonomic and genetic diversity can play complementary roles when it comes to optimizing livestock fodder production in managed grasslands, and suggest that both levels of diversity should be considered in plant breeding programmes designed to boost the productivity and resilience of managed grasslands in the face of increasing environmental hazards.

Molecular Breeding and Functional Genomics for Tolerance to Abiotic Stress

Sustainability is a measure of our ability to produce food with the maximium of efficiency combined with the minimum of damage to the environment. Grasslands represent over 40% of all agricultural land in the European Union, and over 70% in the United Kingdom. Whilst Lolium in Europe is considered to be the ideal source of profitable and safe high quality animal forage, its general poor persistency limits its use to favourable growing areas. Fortunately, genes for abiotic stress resistance are transferred readily from closely related Festuca species by conventional breeding technologies. Introgression mapping allows the assembly of desirable gene combinations and molecular markers to assist with their selection in breeding programmes. Additional new androgenesis techniques have led to novel genotypes rarely observed as outcomes of breeding programmes. Lolium × Festuca hybrids display promiscuous chromosome recombination enabling genes from one species to be transferred readily to homoeologous chromosome regions where they both function normally and remain stable. Despite the close homology between Lolium and Festuca species, repetitive DNA sequences differ sufficiently for their genomes to be distinguished, by genomic in situ hybridisation (GISH). This enables the physical mapping of genes for abiotic stress resistance transferred from Festuca to Lolium. Further chromosome recombination between homoeologous Lolium and Festuca sequences enables Festuca introgressions to be “dissected”, and recombination series created. Knowledge of synteny and gene sequences within model species amongst the Poaceae, combined with the development of sequenced molecular markers, and bacterial artificial chromosomes is enabling the isolation of genes for abiotic stress resistance.

Genetic Improvement in Ryegrass (Lolium perenne) from Turf and Forage Breeding Over the Four Past Decades

In order to assess the efficiency of breeding in ryegrass (Lolium perenne), we tested the agronomic performances of a set of diploid cultivars including turf and forage cultivars registered on European national lists from 1965 to 2004. Seven ecotypes, originating from the main European climatic areas were also tested. Linear regressions fitting agronomic traits to the year of registration enabled to test the genetic improvement in turf and forage breeding through time. The genetic improvement in turf breeding was highly significant (p value of regression slope < 0.001) for most target traits (aesthetic aspect, disease resistance, wear tolerance, summer aspect, persistency). In forage breeding, the genetic improvement was highly significant (p value < 0.001) for autumn dry matter yield, rust resistance, and persistency, and was significant (p value < 0.05) for summer dry matter yield and reduction of aftermath heading. The rate of improvement of annual dry matter yield reached 0.29 ton per 10 years. Forage breeding was additionally associated with a highly significant decrease of lignin and crude protein content, and with a highly significant increase of soluble carbohydrate content. No significant change in grain production was noted either in forage or turf breeding, but conversely a large range of seed production was pointed out in both ancient and recent cultivars.

Festulolium Hybrids: Results, Limits and Prospects

Festulolium refers to natural or synthetic intergeneric hybrids between obligate outbreeding species of the Festuca (fescue) and Lolium (ryegrass) genera, species considered frequently as ideal components of agricultural or turf-grass systems. Festulolium provide specialist function and novel alternatives to existing grass cultivars that may lack resilience against abiotic or biotic stresses. So far, 23 amphiploid Festulolium cultivars have been registered onto national lists as well as 18 cultivars resulting from introgression either into tall fescue or into Italian and perennial ryegrass. Although dispersed throughout the world, Festulolium breeding has considerably stimulated research on genetics of the grasses. This has contributed to the development of numerous new technologies among which Genome In-Situ Hybridization has played an essential role for precision breeding, i.e. monitoring the transfer of selected traits from fescues into diploid Lolium sp. In the future, it would seem very likely that breeding amphiploid Festulolium will also benefit from the genomic advances achieved in diploids using introgression. As future Festulolium cultivars are expected to be extremely diverse, this will require that regulations for registration rely on a genome-based classification and suitable official tests for better acknowledgement of agronomic advances by end-users.

Low Crown Rust Resistance in Norwegian Material of Lolium perenne and × Festulolium

Norwegian cultivars and breeding materials of perennial ryegrass and Festulolium were planted at three locations in Denmark, France and Japan for testing of resistance against leaf diseases. In general, all plant materials were susceptible to crown rust. The highest incidence of rust attack occurred at the French site, which due to its climatic conditions might be the most suitable testing site for future scoring of similar plant material. Entries based on introgressed genetic materials from UK were most resistant towards crown rust. Crown rust resistance needs increased focus as a breeding objective in the Nordic region due to climate changes, which will most likely lead to increased infection of leaf diseases.

Genotyping of Festulolium Cultivars Involved in EUCARPIA Multi-site Trial Using DArT Markers and GISH

A comprehensive set of Festulolium cultivars from on-going field trials in the Eucarpia network was characterised at the chromosome level using genomic in situ hybridization (GISH) and by Diversity Array Technology (DArT) markers. Both technologies were found to be complementary in describing the breeding history of the plant material. The genomic composition of the Lolium × Festuca cultivars varied from those that comprised equivalent proportions of their parental genomes to introgression lines where small chromosome segments of Festuca had been translocated onto Lolium chromosomes. The breadth of genotype combinations found within the grass cultivars described represents an important resource of genetic variations necessary to combat the diverse abiotic stresses encountered within Europe, including safeguards against prolonged exposure to harsh weather conditions. It is likely that in future plant breeding, genotyping will contribute to precision-transfers of targeted Festuca genes into Lolium germplasm in order to enhance resilience to climate change.

Report of the Breeding Debate

Based on a questionnaire with 11 questions, 5 breeding institutes and 4 breeding companies defined their 2035 horizon for grass and forage crops breeding. Visions and opinions differed a lot regarding targeted species, breeding goals, importance of plant physiology, breeding techniques, testing environments, the use of molecular tools and the influence of regulations and sustainability drivers. The report can be considered as a joint reference document for future debates.

Enhancing the productivity in forage grasses on the European scale using interspecific hybridization

Ryegrass x fescue interspecific hybridization (so-called Festulolium) has great potential for forage diversification because of its many amphiploid and introgression-bred forms. Festulolium breeding efforts aim to improve adaptation to mainly winter cold and summer drought through higher abiotic stress tolerance. This goal must be met with a minimum of compromise regarding productivity in the first years of full exploitation. To compare field performances, a 21-entry trial of Festulolium and controls of pure species has been ongoing since 2012 in eight European countries. The yield data collected in 2012 and 2013 in nine locations showed that the Festulolium cultivars performed on average quite well compared to pure species controls. In amphiploids, the annual yield appeared to be mainly driven by the Lolium sp. parent combined with F. pratensis (Fp); the Lm x Fp amphiploids performed thus far better on average than the Lp x Fp equivalents. The only amphiploid from F. glaucescens included in the study had an intermediate response over locations, which was closer to tall fescue than to F. pratensis. Interestingly, a broad variability for yield among the Lm x Fp cultivars appeared to be associated with climate interactions when cold, wet locations were contrasted with more temperate locations with early spring growth.

Genetic Response to Climate Scenarios in Dactylis and Festuca of Temperate Versus Mediterranean Origin

Climate change stresses the importance of exploring the genetic adaptation of plants to an increase of both temperature and water deficit. To this end, dense swards of Mediterranean and temperate cultivars of Dactylis and Festuca were seed harvested after 2 years under artificial climate scenarios (range of summer drought) in two environments (Mediterranean and temperate). To assess possible genetic changes, all populations of the next generation were assessed and compared with their parent population having not been subjected to these climate scenarios. The experiment was a spaced plant design in the temperate location. The results showed that a drought escape strategy through earlier heading time and reduced total plant yield was enhanced by scenarios of greater summer drought. However, the direction and the intensity of the response of the main measured traits suggested that the physiological plant adaptation to water stress differs between species. In Dactylis, the phenology appeared to be a very responsive trait in the late heading temperate cultivar and induced a plant size reduction, while no genetic variability seems to be still available for selection within the early flowering Mediterranean cultivar. By contrast, the balance between both traits was not found so crucial in Festuca which suggests a possible greater role of the rooting system in drought resistance for this species.

Seed Yield of New Festulolium Varieties Bred from F. Arundinacea Var. Glaucescens

In 2007 and 2008, three new amphitetraploid (2n = 4x = 28) Festulolium cultivars were registered on the French National List using for the first time F. arun- dinaceavar.glaucescens Boiss. as a parent. We report hereafter a wide seed yield assessment of those new cultivars together with back-cross derivatives into L. multi- florumorL. perenne and previous Festuloliumcultivars fromF. pratensis. Seed yield of the new F. a.var.glaucescens-derived cultivars was found of same magnitude as amphiploid Festulolium from F. pratensis. However, higher rate of left-over seeds shows that they may be of less intrinsic fertility. We found that total genetic variance was significantly increased between Half-Sibs progenies derived from back-cross intoL. perenne as compared with amphiploid HS progenies. Higher genetic variance between polycrosses of amphiploid L. multiflorum × F. a. var. glaucescens hybrids also suggests that selection for seed yield could take place effectively without nec- essarily individualizing progenies. Seed yield tended to increase over generations of seed multiplication especially when populations derived from back-cross into Lolium sp. It is concluded that the restoration of full seed productivity in Festulolium from F. a. var. glaucescens could be achieved through new Lolium/Festuca genome balance with the development of chromosome/marker-assisted selection procedures.