Impact of foliar diseases in organically grown barley: Influence of fertilization, nutrient content in leaves, varietal disease resistance characteristics and yield potential

Significant increase in severity of powdery mildew,leaf rust and net blotch with increasing N-content in plant leaves 30 days after germination (all years where the relevant diseases were present at a substantial level). This may explain: · Most of the environmental main effects (field) on disease. · Effect of treatments, i.e., treament 4 resulted in reduced N/increased K content in leaves, which coincided with reduced levels of disease. We observed no clear effect of P, Ca, S, and Zn content in leaves on disease. Micronutrients as Cu, Mo and Mn showed significant effects on powdery mildew in one year but not the other; further interpretation may not be possible due to inter-correlation among the effect of micro-nutrients. The diseases had a significant yield reducing effect, in particular powdery mildew and net blotch, which occurred at highest severities. In addition, net blotch affected root development, resulting in significant shorter roots, whereas powdery mildew did not. The effect of disease on root length was of the same order of magnitude as the factor 'variety', but larger than effects of 'year'

Assessment of disease in low-input cereal cropping systems and variety trials

Disease assessment is the basis for describing disease resistance characteristics of commercial varieties in national variety lists for all crops where disease is considered a problem. It is well known that ‘disease’ in a specific situation depends on a whole range of interacting hosts, pathogens and environmental conditions. However, the biological complexity conflicts with the wish to express disease resistance characteristics of a variety as a single score per disease. This problem will be illustrated by basic dynamics of growth and senescence of both host and pathogen over time. Disease expressed in terms of absolute diseased leaf area, disease relative to total leaf area or green leaf area will be discussed in general. Two particular problems in low-input systems will be discussed, i.e. increased variability in nutritional status in field plots, which may influence the balance between abiotic and biotic stresses (diseases) and interact with disease on individual varieties, as well as the influence of weeds and diverse crops (variety mixtures and composite cross populations). The presence of disease in organic and low-input cropping systems may be underestimated because abiotic stresses, which enhance a general senescence of leaves, may obscure disease assessment, in particular disease on leaves. Weeds may interact by harbouring disease showing similar symptoms as on the target crop, or by ‘diluting’ disease by additional healthy green leaf area of the ‘crop’ like in a variety mixture. Other general topics such as differences between host/pathogen systems, timing of assessment, assessment scale, and interpretation and analysis of data are also discussed

Genetic potential for grain yield in spring barley varieties and variety mixtures in variable organic environments

For organic crop production, well-characterised varieties increase the possibilities for controlling diseases and weeds and compensating for deficits in nutrients. Variation in grain yield was studied in about 150 spring barley varieties and variety mixtures and 20 combinations of location, growing system and year. Choice of variety was found to be as important a factor for grain yield as other factors in the management. Some variety mixtures out yielded even the best variety in the mixture, when this was grown in pure stand. Finally, a concept for organic variety testing of spring barley was developed. This Danish project is part of a European COST Network on sustainable low-input cereal production (SUSVAR) which coordinates studies in different countries on variety mixtures, composite crosses and variety testing

Predicting spring barley yield from variety-specific yield potential, disease resistance and straw length, and from environment-specific disease loads and weed pressure

Abstract For low-input crop production, well-characterised varieties increase the possibilities of managing diseases and weeds. This analysis aims at developing a framework for analyzing grain yield using external varietal information about disease resistance, weed competitiveness and yield potential and quantifying the impact of susceptibility grouping and straw length scores (as a measure for weed competitiveness) for predicting spring barley grain yield under variable biotic stress levels. The study comprised 52 spring barley varieties and 17 environments, i.e., combinations of location, growing system and year. Individual varieties and their interactions with environments were analysed by factorial regression of grain yield on external variety information combined with observed environmental disease loads and weed pressure. The external information was based on the official Danish VCU testing. The most parsimonious models explained about 50% of the yield variation among varieties including genotypeenvironment interactions. Disease resistance characteristics of varieties, weighted with disease loads of powdery mildew, leaf rust and net blotch, respectively, had a highly significant influence on grain yield. The extend to which increased susceptibility resulted in increased yield losses in environments with high disease loads of the respective diseases was predicted. The effect of externally determined straw length scores, weighted with weed pressure, was weaker although significant for weeds with creeping growth habit. Higher grain yield was thus predicted for taller plants under weed pressure. The results are discussed in relation to the model ramework, impact of the considered traits and use of information from conventional variety testing in organic cropping systems

Bladsygdomme på byg afhænger af sort, placering i sædskiftet og gødningstype

Plantesygdomme i økologisk planteproduktion har stor indflydelse på produktkvalitet og udbytte. Specielt i korn er der gode muligheder for at forebygge svampesygdomme ved hjælp af sortsresistens, idet mange års planteforædling har bidraget til at øge niveauet af resistens mod de mest betydende svampesygdomme. Dette gælder bl.a. resistens mod bladsvampe som meldug, bygrust, skoldplet og forskellige bladpletsvampe. En sorts resistensniveau mod en given svampesygdom er imidlertid ikke konstant, men kan ændre sig over tid og have forskellig effekt i forskellige dele af landet. Det skyldes primært forskelle og dynamik i de patogenpopulationer, som forårsager de pågældende sygdomme. Derudover er sygdomsniveauet i den enkelte mark afhængig af det lokale smittetryk i begyndelsen af vækstsæsonen, jordens næringsstofbalance- og frigivelse, mikrobiel aktivitet samt vind og vejr

Hvad er en god vårbyg til økologisk jordbrug?

Gennemgang af hvad en god vårbygsort er for økologisk jordbrug. Sortsvalg, udbytte, sortsblandinger, næringsstofoptagelse, ukrudtskonkurrenceevne, sygdomsrobusthed, molekulære markører

Værdien af sygdomsresistens i økologisk dyrket vårbyg

Bladsygdomme kan være et væsentligt problem både i konventionel og økologisk dyrkning af vårbyg. Der er gode muligheder for at forebygge bladsygdomme ved korrekt sortsvalg, såfremt man lægger vægt på sortens (eller sortsblandingens) resistensegenskaber. Det er således afgørende at kende sortens resistens mod specielt de sygdomme, som har størst sandsynlighed for, baseret på den enkeltes erfaringer, at kunne blive et problem. Udover sortsegenskaber vil sygdomsniveauet for den enkelte sygdom i den enkelte mark afhænge af det lokale smittetryk i begyndelsen af vækstsæsonen, jordens næringsstofbalance- og frigivelse, mikrobiel aktivitet samt vind og vejr

Udvikling af kundeattraktivitet over for strategisk vigtige leverandører

God leverandørperformance er ikke en selvfølge. Leverandørperformance afhænger imidlertid af andet end leverandørens evne til at styre egne interne processer. Hvordan leverandører performer, afhænger i høj grad også af kundens attraktivitet. Langt de fleste leverandører foretager således en bevidst prioritering af kunders attraktivitet med udgangspunkt i kunders økonomiske, ressourcemæssige og sociale attraktivitet. Artiklen illustrerer med udgangspunkt i et netværksperspektiv, hvordan JAMO via en bevidst håndtering af sine leverandørrelationer kan prioritere og øge sin kundeattraktivitet, og illustrerer samtidig, hvordan JAMO i praksis kan arbejde med attraktivitetsbegrebet over for seks strategisk vigtige kinesiske leverandører. Attraktivitetsbegrebet har tidligere ikke været forsøgt anvendt i praksis og har overvejende været beskrevet teoretisk

Disease severity and grain yield of spring barley variety mixtures grown under organic and conventional conditions

Despite quite intensive testing of varieties, predictions of future performance of varieties, when grown on specific locations, are known to be nearly impossible; this especially within organic growing systems, where no pesticides and fertilizers can help stabilize yield. Therefore, using mixtures of appropriate varieties might be a way to obtain more stable and acceptable yields. Variety mixtures have so far been studied mostly under conventional farming conditions and focus has often been to characterize disease progress of one pathogen. Here we consider simultaneously four important foliar diseases on spring barley grown in organic as well as conventional growing systems. Further, we study the changes in disease severity of variety mixtures when adapting to local growing conditions (‘farm saved seeds’ or ‘farm varieties’)