Removal of bunt spores from wheat seed lots by brush cleaning

Common bunt is infecting wheat seedling just after sowing, in the heterotrophic phase before seedling emergence. The seed per se is healthy at the time of sowing, but gets infected from spores resting on the seed surface. Bechel et al. 1998 has shown that only a minor fraction of the spores of the the closely related bunt species T.contraversa in a seed lot end up in the flour, while the majority are removed during the cleaning of the seed before or during milling. However, little is known about the destiny of the spores during the cleaning process of seed intented for sowing. Seed lots contaminated with bunt spores during threshing was cleaned in a brush cleaner (ø=400mm) (http://www.westrup.com/HAsideeng.htm) with and without precleaning. Airstream through the cleaner was modified during the project to improve efficacy. It is demonstrated that a brush cleaner can be used to remove spores of common bunt from wheat seed lots. A combined cleaning of a conventional pre-cleaning and a brush cleaning removed 99.8% of the spores in a seed lot. Hence the efficacy of this treatment to prevent seed borne transmission is comparable with the best chemical treatments known. The result indicate that when a the number of bunt spores in a seed lot is assessed, and evaluated in relation to a certain threshold, it should considered if the seed health analysis is made before or after seed cleaning

Organic seed treatment to control common bunt (Tilletia tritici) in wheat

Common bunt caused by the fungus Tilletia tritici (syn. T.caries) is one of the most devastating plant diseases in wheat. In conventional agriculture the disease is controlled exclusively by fungicide seed treatment, but in organic farming these fungicides are not accepted. Previous studies in India have shown that seed treatment with plant extracts of Canabis sativa, Eucalyptus globulus, Thuja sinensis and Datura stramonium was fully effective against the disease under field conditions. Later, in vitro studies have shown that also germination of spores of the Karnal bunt pathogen (Neovossia indica) could be prevented by these plant extracts. The experiment was repeated in Denmark with extracts from the same species grown in Denmark, which has climate conditions very different from India. In this experiment the same seed treatments had no or very limited effect on the frequency of the disease. The treatments were compared with indigenous methods from Europe including salty brine, Thuja leaves and lime. These methods had a significant but insufficient effect on disease suppression

Diversifying cereal production

Modern cereal production has reached a stage of homogeneity, where both environment, nutrition and culinary quality suffers. In order to increase cereal diversity, projects have started investigating heritage varieties, and varieties and species with exotic traits. Well performing varieties and landraces will be used as they are, or will be used as genetic donors in a participatory breeding programme developing composite cross population focussing on disease resistance or special quality traits

Health related effects of wheat varieties

Summarises the different effects wheat digestion has on human healt

Organic seed production and seed regulation

Organic farmers must use organic seed material if such seed are available. If not available, conventional seeds can be used. This request exists in all accredited standards for organic farming. In the EU-regulation on organic production methods, the derogation from the use of organic seed material will only exist until the end of 2003. After this date only organic seed material may be used according to the present formulation. Only a few countries in the EU have an organic seed production able to supply the market for organic seed material. It takes many years to develop a well functioning market for organic seeds. It is therefore unlikely that the derogation for the use of organic seed material will not be extended, since a majority of countries in the EU will still have a need for conventional propagated seeds. However, it will be needed to have standards and control procedures ensuring that organic seeds will be used if available. This includes definitions of “availability”. There is a need in both EU and in accession countries to develop criteria for seeds health in organic seeds and other seeds not treated with fungicides, and to implement inspection procedures to control that conventional seeds are only used when organic seeds are not available

Introductory considerations on crop diversity

Modern society faces decreased biodiversity in nature caused by increased uniformity in agriculture, and health related problems with nutrition caused by industrialisation in food production. Conversion to organic farming increases biodiversity, because of diversification in crops and decreased intensity in control of weed and pests, and increase biochemical diversity within food products because of decreased nitrogen application in field. The author argues that the positive effects of in organic farming can be further improved by improved genetic diversity within the crop. Inter-cropping and variety mixtures are already used by some farmers, but diversity within the crop can be further improved by development of composite cross populations, composition of new stabilized populations, and reintroduction of historic varieties and populations

Control of seed borne diseasees in organic seed propagation

Introduction The key control measure of plant diseases in organic agriculture is crop rotation, mixed cropping and moderate fertilization. A wide range of plant diseases can be controlled or minimized in this way. However, at least one group of plant diseases, the seed borne diseases, cannot. The seed borne diseases are not transmitted through the soil, and crop rotation is therefore an insufficient tool. Mixed cropping is impractical in seed propagation, where seed purity according to the seed legislation is imperative. The fertilization level primarily has an impact on facultative saprophytes, and not on the specialized seed pathogens. Seed borne diseases were the first plant pathogens to be controlled by pesticides. Heavy metals has been used as seed treatments for more than 200 years, and for almost 100 years, the seed borne diseases has been controlled exclusively and very effectively by chemical seed treatments. On this background, research in control of seed borne diseases has had practically no priority in research programs during the last century. Compared with other agricultural topics, the control of seed borne diseases in organic agricultural therefore suffers from the largest lack of knowledge, as we are 100 years behind in research. International seed legislation does with a few exceptions not define minimum quality standards for seed infections with pathogens, as seed sold on the international market normally are treated with fungicides. Surveys show that for some crops, the nationally recommended thresholds for seed pathogens are regularly exceeded in organic seed-lots, and some years the majority of organic seed lots are discarded due to seed borne diseases in propagation systems, where seed health is assessed on a routine basis. To ensure the availability of organic seed for the organic farmers, control measures for seed borne diseases are imperative, and an international system to ensure seed health in organic seed lots should be implemented. Methods to control seed borne diseases in organic agriculture exist. Resistant varieties exist in many cases, and could be used to a wider extent. Different heat treatment can control most seed borne diseases, and new technologies can make this opportunity practical to implement. Technology to separate seed exists, and could be used as a tool to promote the propagation of seed in mixed cropping systems to decrease plant pathogens, including seed pathogens in propagation. Heavy and large seed are generally less infected than small and light seed. The separation and removal of the latter can therefore reduce the infection level in a seed lot. Some seed amendments of natural origin can be used in organic agriculture to replace synthetic pesticides. Ongoing projects Agrologica is currently involved in several projects on control of seed pathogens. This includes 1)heat treatments of cereals by drum-dryer, (Pyrenophora teres, Tilletia tritici, Ascochyta pisi, Fusarium ssp) 2)heat treatments of vegetables seed with steam and ultrasound, (Altanaria radicina, A. petroselini, Cladosporium sp, Septoria Petro, Stemphylium ssp, Phoma lingam, Botrytis ssp, Xantomonas compestris) 3)seed dressings, including plant extracts, smoke, natural chemicals and biological control, 4)physical cleaning of seeds to remove pathogens and infected seeds from seed lots (Ustilago nuda, Pyrenophora graminea, P. teres, T. tritici, Fusarium ssp). 5)integrated control of common bunt (T. tritici) in spelta-wheat (Triticum spelta), 6)preventive cropping methods to reduce build-up of pathogenic fungi during propagation (mixed cropping, early harvest), 7)determining threshold values for organic cereals related to the susceptibility of the individual varieties (P. graminea, P. teres, T. tritici, Ascochyta ssp, Fusarium ssp). Conclusions and recommendations Research during the last two decades has shown that progress can be achieved and that solutions exist. Based on this, it can be concluded that seed borne diseases can be controlled in organic agriculture. However, extension and research to refine methods are urgently needed to do so

Present and future system organisation of organic plant breeding

The paper discuss the perspectives for organic plant breeding in light of biodiversity, EU seed law and the current financing system

Improved quality and disease management in diverse populations

Improved biodiversity is one of the key principles in organic farming and therefore organic plant breeding seeks alternatives to the currently dominant pureline monocultures. Evolutionary plant breeding of composite cross populations (CCPs) has been proposed as a breeding tool for organic plant breeding, where a highly heterogeneous population of offspring is made by mixing a large number of segregating lines from different parents (Döring et al. 2011). Natural selection will, to some extent, reduce traits onferring major disadvantages in a population if these have a high heritability and a significant impact on seed reproduction. It will not, however, necessarily improve baking quality, negative traits with a strong interaction with the environment or minor negative traits. There may be a need, therefore, for improved maintenance breeding and selection to increase yield, disease resistance and quality in populations. Protein content, as a measure of quality, can be improved in a population by seed sorting. Traditional sorting equipment achieved this based on physical characteristics, e.g. seed gravity; novel technologies for high throughput sorting of seed for hardiness and protein content are now available based on image analysis and Near Infrared Spectroscopy (NIRS). Regarding disease resistance in plants, if two parents carry two different resistance genes to a disease, one quarter of the offspring may end up being susceptible due to simple Mendelian distribution. In this way, even after crossing multiple resistant parents, a CCP may end up having higher susceptibility to some diseases than the parental lines. Each cross should therefore be grown, assessed and selected for resistance to relevant diseases individually before eventually combining them to form a CCP. Some diseases, e.g. Fusarium and smut, can produce mycotoxins which have deleterious effects on seed quality even at low levels without a significant impact on grain yield. Hence, resistance to such diseases will not be sufficiently increased by natural selection under common field conditions. In such cases, selection pressure can be augmented artificially by inoculation with fungi to increase infection incidence under controlled conditions. In this way, inoculation can be considered as a breeding tool to improve quality parameters in CCPs. In the CORE2 funded COBRA project, starting in March 2013, these strategies will be tested and further developed. Agrologica have grown CCPs of wheat (jointly developed by the Organic Research Centre and the John Innes Centre UK) since 2007. In parallel, 250 new crosses from 30 parents were made to develop a new population improved resistance to common bunt (Tilletia caries). Research on this material is now under way in the BIOBREED project (Steffan et al. in press). Based on the practical experience from growing CCPs at Agrologica, some considerations for future development of this breeding strategy can be drawn

Resistance to common bunt (Tilletia tritici) and rust (Puccinia sp.) in hulled wheat

Common bunt (Tilletia tritici) and rust diseases (Puccinia sp.) was scored in 123 varieties of wheat species other than bread wheat. The species included Triticum spelta (90 lines), T.macha (18 lines), T.dicoccon (6 lines), T.timopheevii (3 lines) and one representative of each of the species T.vavilovii, T.karamyshevii, T. polonicum, T.carthlicum and T.compactum. Huge differences in bunt susceptibility were found in all species. Lines with low susceptibility were identified in Triticum spelta, T.macha, T.dicoccon, T.timopheevii and T.vavilovii but none in the few investigated lines of species T.karamyshevii, T. polonicum and T.carthlicum. All lines of T.macha, T.vavilovii and T.karamyshevii were susceptible to rust, were as resistance to this disease was frequent in T. spelta. The study hereby has identified candidates for future plant breeding within these species. The lines were also screened for their ability to be sown as spring crops, which can be used as a strategy to control common bunt. Only few lines of T.spelta were of this intermediate type, whereas half of the lines of T.macha, T.dicoccon, T.timopheevii were