Morphological variation in Dutch perennial ryegrass (Lolium perenne L.) populations,in relation to environmental factors

Summary Twenty-one Dutch Lolium perenne populations, fifteen European populations and six L. perenne cultivars were compared for morphological variation. Dutch populations clearly differed from the European populations and the cultivars. Dutch populations generally had reduced plant length and smaller leaves. For other characters, e.g. date of ear emergence, the Dutch populations showed as much variation as the European populations and cultivars they were compared with in this trial. Correlations between morphology and environmental factors at the site of origin were significant in several cases but were generally weak, and dependent on the set of populations studied. In order to maximize the phenotypic differences between the collected populations, soil type and management type appeared to be the most important factors for the choice of collection sites in the Netherlands. To determine suitable collection sites all over Europe, other factors like precipitation, latitude, altitude and temperature factors were also important. For subsampling of the locations, variation in management type within the location determined whether or not phenotypic different samples could be collected. The extensive use of cultivars in the Netherlands does not seem to have prevented the formation of distinct populations. Therefore in situ conservation of grassland seems a good alternative for genetic conservation of L. perenne in the Netherlands.Also associated with the WAU Department of Plant Taxonomy, P.O. Box 8010, 6700 ED, Wageningen, The Netherlands     

A database for a more efficient perennial ryegrass breeding programme

Summary The development and use of a computer database specifically designed to be used to store data from a plant breeding programme on perennial ryegrass (Lolium perenne) is described. Setting up a database requires data analysis in order to establish a conceptual dat model and a conceptual processing data. Every model has been written with MERISE method. With the models, a database has been built using ORACLE relational database management system. It is tailored to meet our own requirements which may be common to other database users.     

Breeding perennial ryegrass for agriculture

Summary Perennial ryegrass has become the most widely sown perennial forage grass in temperate regions due to its combination of high digestibility and tolerance of grazing. The primary objectives in breeding for agricultural use are to improve total and seasonal dry matter production over a range of fertiliser inputs, digestibility, persistency, freezing tolerance and drought or heat tolerance. Adequate seed production and resistance to a wide range of diseases and pests is also necessary. Improvements in productivity and persistency so far have been achieved mainly by hybridisation and recurrent selection using the polycross method and by the use of polyploidy. Further improvements in freezing tolerance, drought and heat tolerance and, for some localities, resistance to pests and snow moulds are required to extend the geographic range of the species. Modern cultivars show little improvement in leaf or stem digestibility but a high magnesium variety is now available. Perennial ryegrass breeding is at an early stage and prospects for further progress appear good.     

Self-Fertile Doubled Haploid Plants of Perennial Ryegrass (Lolium perenne L.)

The self-fertility of chromosome-doubled haploid lines of perennial ryegrass and their first (I₁) and second (I₂) generation selfed offspring was studied. The overall seed set was low, 0—0.4 seeds per spike, as would be expected for chromosome-doubled haploids of a self-incompatible species. Nevertheless, significant genetic variation was observed for self-fertility within three of the six lines studied. Within one line, three I₂-clones showed increased self-fertility, while in two other lines one and three I₁-clones, respectively, showed significantly increased self-fertility. Selection, during selfing, of rare pollen grains with mutations in the self-incompatibility system could explain the observed changes and would lead to a general breakdown of self-incompatibility in Lolium perenne during repeated selfing of chromosome-doubled haploids.     

Evaluating drought resistance in germplasm of meadow fescue

Summary The drought resistance of 25 accessions of meadow fescue (Festuca pratensis Huds.) from seven countries was investigated in four experiments: two in the glasshouse using pot-grown plants from which water was withheld for various periods, and two in controlled environments under osmotic stress.There were significant differences between populations (broad-sense heritabilities or repeatabilities) in all four experiments. In the glasshouse there was a large residual effect of yield potential on production during and after slight-to-moderate drought, and different susceptibilities appeared only after very severe drought. The most consistently high-yielding accessions were from the Bergamo alps in Italy. Recovery after drought was strongly correlated with tiller survival. Continued production under moderate drought was considered important in wetter climates, whereas survival and recovery under severe drought was often associated with low production or flowering in the seeding year, and more typical of summer-drought climates.Leaf growth rates of plants subjected to zero or moderate osmotic stress were correlated with yields of irrigated or moderately-stressed plants in the glasshouse, although there was no differential susceptibility to mild stress. Under severe osmotic stress there were very large differences in survival between populations, but there was no relationship with survival under glasshouse conditions.The inconsistency of population rankings across experiments shows that no one technique gives a full evaluation of drought resistance, and emphasizes the complex nature of the phenomenon. It was possible, however, to identify (a) regions meriting further collections, and (b) ecotypes that had desirable responses in all experiments and could contribute to variety improvement.     

Evidence of pathotypes among Australian isolates of crown rust infecting perennial ryegrass

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.     

A comprehensive multisite recurrent selection strategy in perennial ryegrass

Summary As the seed market for forage grasses in France is rather limited, proposed varieties should have a broad adaptation to a range of different environment. Therefore a comprehensive strategy of multisite recurrent selection has been devised for perennial reyegrass. It is based on an experimental cooperative network between National Institute for Agronomic Research (INRA) and private companies. A pragmatic approach has been retained that gives a compromise between theoretical and practical considerations. The method is illustrated by results from a breeding population consisting of 33 half-sib families derived from a local germplasm. Family selection with an intensity of 30% was applied to yield and persistence data from sward plot trials. The strategy was based on a multisite index where trait x location combinations are considered as different traits and given equal economic weights. Improvements of 10–15% were expected for summer-autumn production and persistence. For spaced plant nursery traits, a subset of locations was chosen according to a multiplicative model decomposition of G x E interaction, where a 10% mass selection was practised. This leads to interesting progress on crown rust tolerance, growth scores, leafiness and persistence. Moreover, the expected indirect responses from selection on spaced plant traits to sward traits and vice-versa are almost all favourable. As significant improvements are expected for most traits in all locations, this programme should allow to increase the general adaptation of ryegrass varieties for France.     

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.     

Performance of Timothy-based Grass/Legume Mixtures in Cold Winter Region

This study sought to identify grass/legume mixtures that increase the yield and persistence of forage stands with improved nutritive quality in cold‐winter regions, compared with the standard mixture of timothy (Phleum pratense L.)/red clover (Trifolium pratense L.)/alsike clover (Trifolium hybridum L.). Timothy was mixed with either perennial ryegrass (Lolium perenne L.), meadow fescue (Festuca pratensis L.) or Kentucky bluegrass (Poa pratensis L.). The legumes in mixtures were red clover, alfalfa (Medicago sativa L.) or white clover (Trifolium repens L.). Averaged over three production years, the majority of mixtures had greater dry matter (DM) yields than the standard (8.35 t ha^?1). Timothy, grown alone and in three mixtures, outyielded the standard by 19–30 %. Yield reductions in mixtures over the 3‐year period were greatest with red clover, and least with bluegrass. Mixtures with alfalfa were highest in nitrogen (28.4 g kg^?1), while grasses grown alone (24.6 g kg^?1) and the standard mixture (25.1 g kg^?1) were the lowest in N. Mixtures with red clover or alfalfa had the least neutral detergent fibre (NDF), averaging 418 and 429 g kg^?1 respectively. Mixtures including white clover were initially low in NDF at 347 g kg^?1 in year 1 but increased to 550 g kg^?1 in year 3 as white clover composition declined in the sward.