Hanne Østergård

Developments in breeding cereals for organic agriculture

The need for increased sustainability of performance in cereal varieties, particularly in organic agriculture (OA), is limited by the lack of varieties adapted to organic conditions. Here, the needs for breeding are reviewed in the context of three major marketing types, global, regional, local, in European OA. Currently, the effort is determined, partly, by the outcomes from trials that compare varieties under OA and CA (conventional agriculture) conditions. The differences are sufficiently large and important to warrant an increase in appropriate breeding. The wide range of environments within OA and between years, underlines the need to try to select for specific adaptation in target environments. The difficulty of doing so can be helped by decentralised breeding with farmer participation and the use of crops buffered by variety mixtures or populations. Varieties for OA need efficient nutrient uptake and use and weed competition. These and other characters need to be considered in relation to the OA cropping system over the whole rotation. Positive interactions are needed, such as early crop vigour for nutrient uptake, weed competition and disease resistance. Incorporation of all characteristics into the crop can be helped by diversification within the crop, allowing complementation and compensation among plants. Although the problems of breeding cereals for organic farming systems are large, there is encouraging progress. This lies in applications of ecology to organic crop production, innovations in plant sciences, and the realisation that such progress is central to both OA and CA, because of climate change and the increasing costs of fossil fuels.

Fitness of backcross and F2 hybrids between weedy Brassica rapa and oilseed rape (B. napus)

With the cultivation of genetically modified crops, transgenes may spread by introgression from crops into weedy and wild populations of related species. The likelihood of this depends in part on the fitness of first and later generation hybrids. We here present results on the fitness of F2 and backcross hybrids between oilseed rape (Brassica napus) and weedy B. rapa. Two populations of B. rapa, two varieties of B. napus, and their F1 hybrids were used for controlled crosses, and seed development, survival in the field, pollen viability, pod- and seed-set were estimated for the offspring. Offspring from F2 and backcrosses had a reduced fitness relative to their parents for most of the fitness components and for a combined estimate of fitness, with F2 offspring suffering the lowest fitness. Despite their lower fitness on average, some of the hybrids were as fit as the parents. Significant fitness differences were detected between backcross and F2 offspring from different B. rapa populations, B. napus varieties, and parental plants. Our results suggest that introgression of transgenes from oilseed rape to B. rapa will be slowed down, but not hindered, by the low fitness of second generation hybrids.

Fitness of F1 hybrids between weedy Brassica rapa and oilseed rape (B. napus)

As part of an ongoing study of the hybridization biology of cultivated oilseed rape (Brassica napus) and weedy B. rapa, we studied the fitness of hybrids between three weedy B. rapa populations and three varieties of B. napus. Reciprocal pollinations were performed, and the resulting offspring were scored for seed development, survival in the field, pod- and seed-set. Seeds from heterospecific crosses developed within pods in lower proportions than seeds from conspecific crosses. Hybrid offspring survived in the field as frequently as conspecific offspring, and produced many more pods that contained fewer seeds. Combining the fitness components into a multiplicative estimate, we found the hybrids to be intermediate to their parents, and significantly more fit than B. rapa. Significant genotypic differences were detected between offspring produced by different parental plants, populations and varieties for some of the fitness components scored. Our results on hybrid fitness are discussed with respect to the possibility that transgenes in oilseed rape may introgress spontaneously into weedy B. rapa.

Comparing the performance of cereal varieties in organic and non-organic cropping systems in different European countries

Top ranking varieties are tested in multiple environments before and after registration in order to assess their value for cultivation and use (VCU testing). Recently, interest has increased in obtaining varieties specifically adapted to organic farming conditions. This raised the question if an independent system of trials may be required for this purpose. To help answering this question, through the exchange network of European cereal researchers SUSVAR (www.cost860.dk), a number of data sets of agronomic traits from barley, wheat and winter triticale, from trials performed in Denmark, Sweden, The Netherlands, France, Switzerland, UK and Germany, were made available and analysed using an approach based on mixed models involving parameters describing genetic correlation between the two types of experiments, i.e., organic and non-organic (high or low input). Estimated variance components and correlations were used to evaluate response to selection and index selection. The response to index selection was analysed as a function of the fraction of available trials assigned to the organic system. The genetic correlations were interpreted in terms of ranking agreement. We found high genetic correlations between both systems for most traits in all countries. Despite high genetic correlations, the chances of very good agreement in observed rankings were moderate. Combining information from both organic and non-organic systems is shown to be beneficial. Further, ignoring information from non-organic trials when making decisions regarding performance under organic conditions is a sub-optimal strategy.

Preferential exclusion of hybrids in mixed pollinations between oilseed rape (Brassica napus) and weedy B. campestris (Brassicaceae).

In most experimental hybridizations between oilseed rape (Brassica napus) and weedy B. campestris, either intra- or interspecific pollen has been applied to individual flowers. Under field conditions, however, stigmas will often receive a mixture of the two types of pollen, thereby allowing for competition between male gametophytes and/or seeds within pods. To test whether competition influences the success of hybridization, pollen from the two species was mixed in different proportions and applied to stigmas of both species. The resulting seeds were scored for paternity by isozyme and randomly amplified polymorphic DNA analysis. Using data on the proportion of fully developed seeds and the proportion of these seeds that were hybrids, a statistical model was constructed to estimate the fitness of conspecific and heterospecific pollen and the survival of conspecific and heterospecific zygotes to seeds. B. campestris pollen in B. napus styles had a significantly lower fitness than the conspecific pollen, whereas no difference between pollen types was found in B. campestris styles. Hybrid zygotes survived to significantly lower proportions than conspecific zygotes in both species, with the lowest survival of hybrid zygotes in B. napus pods. This is in contrast to the higher survival of hybrid seeds in B. napus than in B. campestris pods when pollinations are made with pure pollen. Altogether, the likelihood of a foreign pollen grain producing a seed was much lower on B. napus than on B. campestris. In addition, pods on B. napus developed to a lower extent the more heterospecific pollen was in the mix, whereas this had no effect on B. campestris.

The role of molecular markers and marker assisted selection in breeding for organic agriculture

Plant geneticists consider molecular marker assisted selection a useful additional tool in plant breeding programs to make selection more efficient. Standards for organic agriculture do not exclude the use of molecular markers as such, however for the organic sector the appropriateness of molecular markers is not self-evident and is often debated. Organic and low-input farming conditions require breeding for robust and flexible varieties, which may be hampered by too much focus on the molecular level. Pros and contras for application of molecular markers in breeding for organic agriculture was the topic of a recent European plant breeding workshop. The participants evaluated strengths, weaknesses, opportunities, and threats of the use of molecular markers and we formalized their inputs into breeder’s perspectives and perspectives seen from the organic sector’s standpoint. Clear strengths were identified, e.g. better knowledge about gene pool of breeding material, more efficient introgression of new resistance genes from wild relatives and testing pyramided genes. There were also common concerns among breeders aiming at breeding for organic and/or conventional agriculture, such as the increasing competition and cost investments to get access to marker technology, and the need for bridging the gap between phenotyping and genotyping especially with complex and quantitative inherited traits such as nutrient-efficiency. A major conclusion of the authors is that more interaction and mutual understanding between organic and molecular oriented breeders is necessary and can benefit both research communities.

Statistical prediction of biomethane potentials based on the composition of lignocellulosic biomass

Mixture models are introduced as a new and stronger methodology for statistical prediction of biomethane potentials (BPM) from lignocellulosic biomass compared to the linear regression models previously used. A large dataset from literature combined with our own data were analysed using canonical linear and quadratic mixture models. The full model to predict BMP (R(2)>0.96), including the four biomass components cellulose (xC), hemicellulose (xH), lignin (xL) and residuals (xR=1-xC-xH-xL) had highly significant regression coefficients. It was possible to reduce the model without substantially affecting the quality of the prediction, as the regression coefficients for xC, xH and xR were not significantly different based on the dataset. The model was extended with an effect of different methods of analysing the biomass constituents content (DA) which had a significant impact. In conclusion, the best prediction of BMP is pBMP=347xC+H+R-438xL+63DA.

Transfer of engineered genes from crop to wild plants

The escape of engineered genes — genes inserted using recombinant DNA techniques — from cultivated plants to wild or weedy relatives has raised concern about possible risks to the environment or to health. The media have added considerably to public concern by suggesting that such gene escape is a new and rather unexpected phenomenon. However, transfer of engineered genes between plants is not at all surprising, because it is mediated by exactly the same mechanisms as those responsible for transferring endogenous plant genes: it takes place by sexual crosses, with pollen as the carrier. Such sexual reproduction has been the basis for breeding almost all crops.

Effects of inter-varietal diversity, biotic stresses and environmental productivity on grain yield of spring barley variety mixtures

Varietal seed mixtures tend to increase and stabilize crop yields, yet their application is sparse. Large-scale cultivation of variety mixtures may require a better understanding of how inter-varietal interactions and their interaction with the environment may influence the grain yield of variety mixtures relative to their component varieties. For this purpose, six variety mixtures of spring barley and 14 component varieties were grown in each of 17 trial environments. A total of 28 observed and a priori plant characteristics, including grain yield, disease severity and weed competitiveness, were derived for each component variety in each trial. The relationship between inter-varietal diversity of each characteristic and the mixing effect on grain yield was analysed. Additionally, various types of yield stability were estimated and compared among mixtures and component varieties. One mixture out-yielded all of its component varieties in almost half of the trial environments. Inter-varietal diversity in grain yield potential correlated significantly with mixing effect, as did straw length diversity when weighted with weed pressure. The grain yields of most mixtures were more stable across environments than their component varieties when accounting also for the general response to environmental productivity. Hence, most mixtures adapted slightly better to environmental productivity and were less sensitive to environmental stress than their component varieties. We conclude that the efficacy of variety mixtures may be enhanced by mixing relatively high-yielding varieties differing in responsiveness to environmental productivity.

Preface to the special issue: Plant breeding for organic and sustainable, low-input agriculture: dealing with genotype-environment interactions

In Europe, agriculture is increasingly moving towards organic and sustainable, low-input farming systems. These agricultural practices, however, have various constraints that still need to be solved. One of the major constraints of organic farmers is that they largely depend on crop varieties produced for conventional farming systems with high inputs of artiWcial, mineral fertilizers and chemicals for crop defense. Therefore, the organic sector urgently requires breeding programmes for robust varieties, which are better adapted to low-input conditions, with traits such as improved rooting systems, stronger interspeciWc competition ability for weed suppression and yield stability. An important aspect in the breeding for such varieties is the choice for an appropriate selection environment or a combination of environments: organic versus conventional and highversus lowinput conditions. Recognising the above mentioned constraints and the need to explore alternative strategies to overcome these constraints, hereby also using insight and knowledge from agronomic Welds working at a higher aggregation level (i.e. system level), the Wrst EUCARPIA meeting of the Section Organic plant breeding and low-input agriculture was organised in Wageningen, the Netherlands, from 7 to 9 November 2007. This symposium was organised in close cooperation with COST860 SUSVAR, the European Consortium for Organic Plant breeding (ECO-PB), ISOFAR section Plant Breeding and Seed Production, the C.T. de Wit Graduate School for Production Ecology and Resource Conservation (PE&RC) and the Chair Organic Plant Breeding of Wageningen University. Some 130 participants representing 28 countries attended the symposium, including students, researchers and other professionals from universities, institutes and breeding companies. The programme featured 17 oral and 47 poster presentations, covering the topic areas of genotype–environment interaction, breeding strategies, selection criteria and methods, and participatory breeding approaches. A book of abstracts was available at the symposium including abstracts of all the presentations, see www.eucarpia.org. A selection of presentations were regarded as representing the four topic areas and are combined as full papers in this special issue of Euphytica, the international plant breeders’ journal. We are grateful to the editor-in-chief professor Dr. Richard Visser, for supporting the publication E. T. Lammerts van Bueren (&) Wageningen UR Plant Breeding, Wageningen University, P.O. Box 386, 6700 AJ Wageningen, The Netherlands e-mail: edith.lammertsvanbueren@wur.nl