Sammendrag

Sclerotinia stem rot (SSR) is the most important disease of oilseed Brassica crops in Norway. Fungicide applications should be aligned with the actual need for control, but the SSR prediction models used lack accuracy. We have studied the importance of precipitation, and the role of petal and leaf infection for SSR incidence by using data from Norwegian field and trap plant trials over several years. In the trials, SSR incidence ranged from 0 to 65%. Given an infection threshold of 25% SSR, regression and Receiver Operating Characteristics (ROC) analysis were used to evaluate different precipitation thresholds. The sum of precipitation two weeks before and during flowering appeared to be a poor predictor for SSR infection in our field and trap plant trials (P = 0.24, P = 0.11, respectively). Leaves from three levels (leaf one, three, five), and petals were collected at three to four different times during flowering from nine field sites over two years and tested for SSR infection with real-time PCR. Percentage total leaf and petal infection explained 57 and 45% of variation in SSR incidence, respectively. Examining the different leaves and petals separately, infection of leaf three sampled at full flowering showed the highest explanation of variation in later SSR incidence (R2 = 65%, P < 0.001). ROC analysis showed that given an infection threshold of 45%, both petal and leaf infection recommended spraying when spraying was actually needed. Combining information on petal and leaf infection during flowering with relevant microclimate factors in the canopy, instead of the sum of precipitation might improve prediction accuracy for SSR.

Til dokument

Sammendrag

The estimated potential yield losses caused by plant pathogens is up to 16% globally (Oerke 2006) and most research in plant pathology aims to reduce yield loss in our crops directly or indirectly. Yield losses caused by a certain disease depend not only on disease severity, but also on the weather factors, the pathogen’s aggressiveness, and the ability of the crop to compensate for reduced photosynthetic area. The yield loss-disease relationship in a certain host-pathogen system might therefore change from year to year, making predictions for yield loss very difficult at the regional or even at the farmer’s level. However, estimating yield losses is essential to determine disease management thresholds at which acute control measures such as fungicide applications, or strategic measures such as crop rotation or use of resistant cultivars are economically and environmentally sensible. Legislation in many countries enforces implementation of integrated pest management (IPM), based on economic thresholds at which the costs due to a disease justify the costs for its management. Without a better understanding of the relationship between disease epidemiology and yield loss, we remain insufficiently equipped to design adequate IPM strategies that will be widely adapted in agriculture. Crop loss studies are resource demanding and difficult to interpret for one particular disease, as crops are usually not invaded by only one pest or pathogen at a time. Combining our knowledge on disease epidemiology, crop physiology, yield development, damage mechanisms involved, and the effect of management practices can help us to increase our understanding of the disease-crop loss relationship. The main aim of this paper is to review and analyze the literature on a representative host-pathogen relationship in an important staple food crop to identify knowledge gaps and research areas to better assess yield loss and design management strategies based on economic thresholds. Wheat is one of the most important staple foods worldwide and is susceptible to several important plant diseases. In our article, we focus on Septoria nodorum blotch (SNB) or Glume blotch of wheat as an example for a stubble-borne, seed-transmitted disease with a worldwide distribution causing considerable and regular yield losses. In their review on yield losses due to wheat pathogens in Australia, Murray and Brennan (2009) estimated the current annual economic loss due to SNB as high as $108 × 106, with potential costs as high as $230 × 106. The causal fungus, Parastagonospora nodorum, is currently serving as a model organism for molecular studies of the intimate relationship between necrotic effector-producing fungal strains and their corresponding susceptibility genes present in wheat cultivars (Oliver et al. 2012). In this paper, we analyze the literature on the biology of this common wheat pathogen, the yield loss it reportedly has caused, and the effect of control strategies to reduce this loss. Based on this analysis, we will evaluate the use of common management practices to reduce disease-related yield loss and identify related research needs.

Til dokument

Sammendrag

During August 2013, white-grayish lesions, typical of Sclerotinia stem rot, had developed around leaf axils on the stems of turnip rape ‘Pepita’ in a field at the NIBIO research station Apelsvoll in Oppland County, Norway. Sclerotia were collected from inside infected turnip rape stubble and from harvested seeds, surface sterilized, bisected, and placed onto potato dextrose agar (PDA). Following 1 to 2 days incubation at 20°C, fast-growing white mycelium characteristic of Sclerotinia was observed, and within 5 to 7 days, new sclerotia had started to develop. Sclerotia size and growing pattern although variable was characteristic of S. sclerotiorum. DNA extraction, PCR amplification, and sequencing of the ITS regions of the rDNA was then carried out for 20 isolates. BLASTn analysis of 475 bp amplicons showed that 15 isolates were S. sclerotiorum, while five were identified as S. subarctica (previously called Sclerotinia sp 1; Holst-Jensen et al. 1998; Winton et al. 2006, 2007), with 100% identity to a U.K. S. subarctica isolate (Clarkson et al. 2010). A representative ITS region sequence was deposited in GenBank (accession no. KX929095). The identity of the S. subarctica isolates was further confirmed by the lack of a 304-bp intron in the LSU rDNA compared with S. sclerotiorum (Holst-Jensen et al. 1998), which was visualized by PCR amplification and gel electrophoresis. Sclerotia of two S. subarctica isolates were placed on PDA and incubated for 7 days. Agar plugs of actively growing mycelium were used for the pathogenicity testing of spring oilseed rape plants (‘Mosaik’) in the greenhouse. Plants were inoculated at growth stage BBCH 57/59 (preflowering) and BBCH 64 (40% of flowers open) by attaching two PDA plugs of actively growing mycelium per main stems with small needles, using four plants per treatment. Noninoculated PDA agar plugs were attached to the control plants. The experiment was repeated three times. Symptoms typical of stem rot appeared after 1 to 2 weeks of incubation at 16 to 20°C, 100% relative humidity. Stems started to develop white lesions with fluffy mycelium around the inoculation sites. Control plants did not show the characteristic symptoms for Sclerotinia infection. After senescence of the plants, sclerotia were collected from inside the stems and cultured on PDA. White mycelium started to grow after 1 to 2 days and new sclerotia were formed within 7 days, similar to the ones used for producing the initial isolate. Brassica oil seed crops are cultivated as important break crops in the cereal-based production system in Norway and can be severely affected by Sclerotinia stem rot. The disease is observed in all regions where Brassica oil seed crops are grown, and in severe cases, a reduction in oilseed yield of 25% has been recorded in untreated control treatments of fungicide trials. Although S. subarctica has been previously reported on wild hosts (Holst-Jensen et al. 1998), this is the first report of the pathogen on a crop plant in Norway. In the United Kingdom, Clarkson et al. (2010) demonstrated pathogenicity of S. subarctica isolated from Ranunculus acris on oilseed rape. As symptoms for S. subarctica and S. sclerotiorum are indistinguishable, S. subarctica might be present undetected in many farmer fields.

Til dokument

Sammendrag

Net blotch, caused by the necrotrophic fungus Pyrenophora teres, is one of the major diseases in barley in Norway causing quantitative and qualitative yield losses. Resistance in Norwegian cultivars and germplasm is generally insufficient and resistance sources have not been extensively explored yet. In this study, we mapped quantitative trait loci (QTL) associated with resistance to net blotch in Nordic germplasm. We evaluated a collection of 209 mostly Nordic spring barley lines for reactions to net form net blotch (NFNB; Pyrenophora teres f. teres) in inoculations with three single conidia isolates at the seedling stage and in inoculated field trials at the adult stage in 4 years. Using 5669 SNP markers genotyped with the Illumina iSelect 9k Barley SNP Chip and a mixed linear model accounting for population structure and kinship, we found a total of 35 significant marker-trait associations for net blotch resistance, corresponding to 13 QTL, on all chromosomes. Out of these QTL, seven conferred resistance only in adult plants and four were only detectable in seedlings. Two QTL on chromosomes 3H and 6H were significant during both seedling inoculations and adult stage field trials. These are promising candidates for breeding programs using marker-assisted selection strategies. The results elucidate the genetic background of NFNB resistance in Nordic germplasm and suggest that NB resistance is conferred by a number of genes each with small-to-moderate effects, making it necessary to pyramid these genes to achieve sufficient levels of resistance.

Til dokument

Sammendrag

Barley net blotch caused by the necrotrophic fungus Pyrenophora teres is a major barley disease in Norway. It can cause grain shriveling and yield losses, and resistance in currently grown cultivars is insufficient. In this study, a set of 589 polymorphic SNP markers was used to map resistance loci in a population of 109 doubled haploid lines from a cross between the closely related Norwegian cultivars Arve (moderately susceptible) and Lavrans (moderately resistant). Resistance to three net form net blotch (P. teres f. teres) single spore isolates was evaluated at the seedling stage in the greenhouse and at the adult plant stage under field conditions during three years. Days to heading and plant height were scored to assess their influence on disease severity. At the seedling stage, three to four quantitative trait loci (QTL) associated with resistance were found per isolate used. A major, putatively novel QTL was identified on chromosome 5H, accounting for 23±48% of the genetic variation. Additional QTL explaining between 12 and 16.5% were found on chromosomes 4H, 5H, 6H and 7H, with the one on 6H being race-specific. The major QTL on 5H was also found in adult plants under field conditions in three years (explaining up to 55%) and the 7H QTL was found in field trials in one year. Additional adult plant resistance QTL on 3H, 6H and 7H were significant in single years. The resistance on chromosomes 3H, 5H, 6H and 7H originates from the more resistant parent Lavrans, while the resistance on 4H is conferred by Arve. The genetic markers associated with the QTL found in this study will benefit marker-assisted selection for resistance against net blotch.

Sammendrag

Det er per i dag påvist resistens eller nedsatt følsomhet mot kjemiske plantevernmidler hos flere skadedyr, plantepatogener og ugras i norske jord- og hagebrukskulturer. Hos skadedyr er resistens mot pyretroider og nedsatt følsomhet for tiakloprid vanlig hos rapsglansbille i oljevekster. Resistens mot pyretroider er påvist hos ferskenbladlus og potetsikade fra potet, gulrotsuger fra gulrot, ferskenbladlus fra persille, kålmøll og ferskenbladlus fra kålvekster, jordbærsnutebille fra jordbær, og ferskenbladlus, bomullsmellus, veksthusmellus og sør-amerikansk minerflue fra veksthus. Det er også funnet resistens mot pirimikarb hos ferskenbladlus og nedsatt følsomhet for imidakloprid hos ferskenbladlus og bomullsmellus. I jordbær og bringebær er det indikasjoner på begynnende resistensutvikling mot flere av middmidlene. Hos plantepatogener er resistens mot QoI-fungicider påvist hos gråskimmel fra jordbær, bringebær og gran i skogplanteskoler, hos mjøldoggsopper i jordbær og veksthusagurk, og hos bladflekksopper i hvete. Resistens mot triazoler er funnet i flere bladflekksopper i hvete. Resistens mot hydroksyanilid- og SDHI-er utbredt hos gråskimmel fra jordbær og bringebær, og i skogplanteskoler er det påvist resistens mot tiofanater.....

Sammendrag

Researchers in plant pathology and entomology often study the interaction between a host plant and its pathogen or an insect pest separately. Although studying single pathogen or insect interactions with a host plant is critical to understand the basic infection processes and to model each disease or pest attack separately, this is an extreme simplification of nature’s complexity, where multiple pests and pathogens often appear in parallel and interact with each other and their host plant. Effective management of pests and diseases require understanding of the complex interaction beteween diseases and pests on the host. Under natural conditions, wheat plants are subjected to attack by several insects and pathogens simultaneously or sequentially. The Bird cherry-oat aphid (Rhopalosiphum padi) and the necrotrophic pathogen Parastagonospora nodorum (syn. Stagonospora nodorum) the causal agent of Stagonospora nodorum blotch (SNB) are economically important pests of wheat in Norway. Since they colonize a common host, they may interact directly through competition for resources or indirectly by affecting the host response either positively (induced resistance) or negatively (induced susceptibility or biopredisposition). The effect of aphid infestation on P. nodorum infection and development of the disease could be an important factor in predicting SNB epidemics. However, studies on this multitrophic interactions are scarce. We conducted controlled greenhouse experiments to study the effect of aphid infestation on subsequent SNB development. The wheat cultivar ‘Bjarne’ was treated as follows:1) Aphid infested + insecticide sprayed + P. nodorum inoculated; 2) Insecticide sprayed + P. nodorum inoculated; 3) Water sprayed + P. nodorum inoculated; 4) Control plants (without aphid, insecticide or P. nodorum). When plants were at ca. BBCH 37, 18 adult female aphids (R. padi) were released per pot (treatment 1). Aphid inoculated plants were kept in an insect proof cage in a greenhouse compartment at 20°C, 70% RH, and 16 h photoperiod. Plants for the other treatments were kept in separate insect proof cages in the same greenhouse. Ten days after aphid release, plants infested with aphids (treatment 1) were sprayed with the insecticide BISCAYA (a.i. thiacloprid) at recommended concentration to remove aphids. Plants in treatment 2 and 3 were sprayed with the insecticide and water, respectively. Twenty-four hours after application of the insecticide or water, plants in treatment 1, 2, and 3 were inoculated with P. nodorum spore suspension (106 spores ml-1). The experiment included three replicates and was repeated two times. SNB incidence and severity were recorded. SNB incidence and severity were significantly higher on aphid infested plants than on non-infested plants (P < 0.05). Ten days after P. nodorum inoculation, disease severity were about 3-fold higher on aphid infested plants (treatment 1) than on non-infested plants (treatment 2 and 3). Plants in the blank control (treatment 4) were free of aphids and showed no symptoms of SNB . Infestation of wheat plants by the bird cherry-oat aphid prior to fungal inoculation enhanced the severity of SNB. P. nodorum is a necrotrophic pathogen that lives on nutrients from disintegrated plant cells. The increase in severity of SNB on aphid infested plants could be due to the increased number of dead or dying cells around the aphids feeding sites. However, whether aphids activity induced local or systemic susceptbility to plants is not yet known and needs to be studied further.

Sammendrag

The necrotrophic fungus Drechslera teres causes net blotch disease in barley by secreting necrotrophic effectors (NEs) which, in the presence of corresponding host susceptibility factors (SF), act as virulence factors in order to enable host colonization. At present the resistance within most Norwegian cultivars is insufficient. This study aims at detecting QTL associated with resistance and susceptibility in the Nordic barley breeding material and at discovering new NE _ SF interactions. This knowledge together with an understanding of the genetic background of the Norwegian net blotch population will be utilized to speed up resistance breeding. Resistance of a segregating mapping population of a cross between the closely related Norwegian varieties Arve and Lavrans to three Norwegian D. teres isolates was assessed at seedling stage in the greenhouse and in adult plants in the field. QTL mapping revealed four major QTL on chromosomes 4H, 5H, 6H and 7H. The 5H and 6H QTL accounted for up to 47% and 14.1% of the genetic variance, respectively, and were found both in seedlings and adult plants with the latter QTL being an isolate-specific association. The high correlation of seedling and adult resistance (R2=0.49) suggests that components of adult plant resistance can be predicted already at the seedling stage. Selected isolates and their culture filtrates will be screened on selected barley lines to characterize novel NE - SF interactions and to map the corresponding sensitivity loci. Effector protein candidates will be purified and further analysed to verify their effect on disease development. Additionally, 365 Norwegian D. teres isolates and a selection of globally collected isolates are currently being ddRAD genotyped in order to obtain SNP markers to study the genetic diversity and population structure of the current Norwegian fungal population. This data will also allow us to perform Genome Wide Association Studies (GWAS) to identify potential novel NE genes.

Sammendrag

Net blotch is a major barley disease in Norway caused by the necrotrophic fungus Drechslera teres leading to yield losses of up to 40%. At present, resistance of Norwegian cultivars is insufficient. The pathogen secretes necrotrophic effectors (NEs) which act as virulence factors in order to gain entry into and nutrients from the host (Liu et al., 2014). NEs cause a hypersensitive response in the presence of corresponding dominant host susceptibility factors. In this study we examine the potential role of NEs and host receptors in explaining susceptibility to net blotch in Norwegian barley. This knowledge together with an understanding of the genetic background of the Norwegian net blotch population will be utilized to speed up resistance breeding. 365 Norwegian D. teres isolates collected from various regions and years, together with a selection of globally collected isolates, will be RADtag genotyped in order to obtain GBS markers to study the genetic diversity, genomic evolution and population structure of the current Norwegian fungal population and to compare it to pathotypes from other countries. Additionally, this data will allow us to perform Genomewide Association Studies (GWAS) to identify potential novel NE genes. Selected isolates and their culture filtrates will be screened for specific reactions against an association mapping panel of ca. 200 mostly Norwegian barley lines and a biparental mapping population (both genotyped with the Illumina barley 9K chip) to characterize novel NE-host susceptibility interactions and to map the corresponding sensitivity loci. Effector protein candidates will be purified and further analysed to verify their effect on disease development.

Sammendrag

Net blotch is a major barley disease in Norway caused by the necrotrophic fungus Drechslera teres leading to yield losses of up to 40%. At present, resistance of Norwegian cultivars is insufficient. The pathogen secretes necrotrophic effectors (NEs) which act as virulence factors in order to gain entry into and nutrients from the host (Liu et al., 2014). NEs cause a hypersensitive response in the presence of corresponding dominant host susceptibility factors. In this study we examine the potential role of NEs and host receptors in explaining susceptibility to net blotch in Norwegian barley. This knowledge together with an understanding of the genetic background of the Norwegian net blotch population will be utilized to speed up resistance breeding. 365 Norwegian D. teres isolates collected from various regions and years, together with a selection of globally collected isolates, will be RADtag genotyped in order to obtain GBS markers to study the genetic diversity, genomic evolution and population structure of the current Norwegian fungal population and to compare it to pathotypes from other countries. Additionally, this data will allow us to perform Genomewide Association Studies (GWAS) to identify potential novel NE genes. Selected isolates and their culture filtrates will be screened for specific reactions against an association mapping panel of ca. 200 mostly Norwegian barley lines and a biparental mapping population (both genotyped with the Illumina barley 9K chip) to characterize novel NE-host susceptibility interactions and to map the corresponding sensitivity loci. Effector protein candidates will be purified and further analysed to verify their effect on disease development.

Sammendrag

In Europe there is an on-going process on implementing regulations aimed at reducing pollution from agricultural production systems, i.e. the Water Framework Directive and the Framework Directive for Sustainable Use of Pesticides. At the same time, there is an increasing focus on food security possibly leading to continued intensification of agricultural production with increased use of external inputs, such as pesticides and fertilizers. Application of sustainable production systems can only be achieved if they balance conflicting environmental and economic effects. In Norway, cereal production is of large importance for food security and reduction of soil and phosphorus losses, as well as pesticide use and leaching/runoff in the cereal production are of special concern. Therefore, we need to determine the most sustainable and effective strategies to reduce loss of top soil, phosphorus and pesticides while maintaining cereal yields. A three-year research project, STRAPP, is addressing these concerns. A catchment area dominated by cereal production is our common research arena within STRAPP. Since 1992 a database (JOVA) with data for soil erosion, nutrient and pesticide leaching/runoff (i.e. concentrations in stream water), yield, and agricultural management practices (fertilization, use of pesticides, soil tillage and rotations) has been established for this catchment allowing us to compare a unique diversity in cropping strategies in a defined location. An important part of STRAPP focuses on developing ‘best plant protection strategies’ for cereal fields in the study area, based on field inventories (manual and sensor based) of weeds and common diseases, available forecast systems, and pesticide leaching risk maps. The results of field studies during the growing seasons of 2013 and 2014 will be presented, with a focus on possible integrated pest management (IPM) strategies for weeds and fungal diseases in cereal production. We will also present the project concept and methods for coupling optimized plant protection strategies to (i) modelling of phosphorus and pesticide leaching/runoff, as well as soil loss, and (ii) farm-economic impacts and adaptations. Further, methods for balancing the conflicting environmental and economic effects of the above practices, and the evaluation of instruments for increased adoption of desirable management practices will be outlined.

Sammendrag

Leaf blotch diseases in wheat can cause yield losses above 30 %. The necrotrophic fungus Parastagonospora nodorum is the dominating leaf blotch pathogen in Norwegian spring wheat. It has been well documented at the seedling stage that the pathogen produces necrotrophic effectors (NEs) which induces cell death in plants carrying susceptibility genes (Snn), allowing the necrotroph to enter. However, the role of these interactions under field conditions is less researched. In this study, we conducted field experiments with bi-parental and association mapping populations of spring wheat, to investigate the role of NE/Snn in adult plant resistance. The populations have been genotyped with the Illumina 90 K SNP chip, P. nodorum has high genetic diversity and both sexual and asexual reproduction, but the actual adaptation of the pathogen population to cultivars with different levels of resistance is not well studied. We are screening a collection of Norwegian isolates from known host sources to look for differences in NE-frequencies and haplotype distribution. The mapping populations are also inoculated and infiltrated with culture filtrates from single isolates on the seedling stage. Isolates involved in novel interactions will be deepsequenced in order to look for candidate effector genes. Potential effector proteins will be purified by LPC and HPLC to confirm their role in disease development.

Sammendrag

Leaf blotch diseases in wheat can cause yield losses above 30 %. The necrotrophic fungus Parastagonospora nodorum is the dominating leaf blotch pathogen in Norwegian spring wheat. It has been well documented at the seedling stage that the pathogen produces necrotrophic effectors (NEs) which induces cell death in plants carrying susceptibility genes (Snn), allowing the necrotroph to enter. However, the role of these interactions under field conditions is less researched. In this study, we conducted field experiments with bi-parental and association mapping populations of spring wheat, to investigate the role of NE/Snn in adult plant resistance. The populations have been genotyped with the Illumina 90 K SNP chip, P. nodorum has high genetic diversity and both sexual and asexual reproduction, but the actual adaptation of the pathogen population to cultivars with different levels of resistance is not well studied. We are screening a collection of Norwegian isolates from known host sources to look for differences in NE-frequencies and haplotype distribution. The mapping populations are also inoculated and infiltrated with culture filtrates from single isolates on the seedling stage. Isolates involved in novel interactions will be deepsequenced in order to look for candidate effector genes. Potential effector proteins will be purified by LPC and HPLC to confirm their role in disease development.

Sammendrag

Forsøksresultatene som presenteres i denne rapporten er biologisk godkjenningsprøving av soppmidler utført på oppdrag fra Mattilsynet i 2014. Inkludert i rapporten er også forsøk eller egne forsøksledd som grupperes som biologisk utviklingsprøving. Forsøkene er utført etter GEP-kvalitet1 hvis ikke annet er nevnt. Dette innebærer at det er utarbeidet skriftlige prosedyrer for nesten alle arbeidsprosesser. Disse prosedyrene, kalt standardforskrifter (SF’er), er samlet i en kvalitetshåndbok. Denne er delt ut til alle personer som arbeider med utprøving av plantevernmidler. De samme personene har også vært med på et endagskurs i GEP-arbeid.

Sammendrag

Forsøksresultatene som presenteres i denne rapporten er biologisk godkjenningsprøving av soppmidler utført på oppdrag fra Mattilsynet i 2012. Inkludert i rapporten er også forsøk eller egne forsøksledd som grupperes som biologisk utviklingsprøving. Forsøkene er utført etter GEP-kvalitet1 hvis ikke annet er nevnt. Dette innebærer at det er utarbeidet skriftlige prosedyrer for nesten alle arbeidsprosesser. Disse prosedyrene, kalt standardforskrifter (SF’er), er samlet i en kvalitetshåndbok. Denne er delt ut til alle personer som arbeider med utprøving av plantevernmidler. De samme personene har også vært med på et endagskurs i GEP-arbeid.

Sammendrag

Plogen har tradisjonelt vært viktig for å få et godt såbed, for innblanding av halmrester og gjødsel i jorda, og for god bekjemping av ugras og sjukdommer. Redusert jordarbeiding uten bruk av plogen, gir imidlertid store miljøfordeler i form av mindre erosjon og utvasking av næringsstoffer. Denne rapporten fokuserer på konsekvenser av ulik jordarbeiding på plantevernsituasjonen i korn. Basert på dagens kunnskap fra norske og internasjonale studier konkluderes det med at redusert jordarbeiding gir økt risiko for utvikling av ugras og plantesjukdommer, samt mykotoksiner. I tillegg kan redusert jordarbeiding føre til økt bruk av kjemiske plantevernmidler som glyfosat, fenoksysyrer og soppmidler. Ugraset og de fleste plantesjukdommer kan som regel bekjempes med plantevernmidler, mens Fusarium spp. og mykotoksiner bare delvis kan bekjempes av kjemiske midler. Miljørisikoen av kjemiske plantevernmidler påvirkes av egenskaper til plantevernmidlene. Redusert jordarbeiding fører til økt risiko for transport til grunnvann av fenoksysyrer og lavdosemidler (sulfonylurea-preparater). Risiko for transport til overflatevann av ugrasmidler og soppmidler er minst når åkeren ligger i stubb. Været og klimaet har stor betydning for utvikling av skadegjørerne, risiko for utvikling av mykotoksiner og utvasking av plantevernmidler. Vårpløying kan være gunstig miljømessig sett fordi det kan redusere erosjon og næringsstofftap. Samtidig gir det mindre behov for, og derfor redusert miljørisiko av, plantevernmidler enn andre typer jordarbeiding. Vårpløying egner seg derimot dårlig på stiv leirjord, det fører til større tidspress på våren og risiko for forsinka våronn og derved lavere avling.

Sammendrag

Three primary causal agents are involved in the leaf blotch disease (LBD) complex of Norwegian winter and spring wheat: Phaesophaeria nodorum, Mycospaerella tritici, and Pyrenophora drechslera-tritici. The dynamics of symptom development, similarity of symptoms caused by each agent, and confounding of disease symptoms by leaf senescence interfere with accurate assessment of disease. Empirical and regression models for disease and yield loss forecasting are only as good as the data upon which they are based. Accurately describing the relationship between symptoms and yield loss is therefore critical to meaningful economic thresholds for management decisions and advisory systems. A general guideline for yield loss and disease severity has been described as 1% yield loss per 1% disease severity on the flag leaf at BBCH stage 70-75 (King et al., 1983).  However, several years of field trials in Norway indicate that disease severity can increase exponentially during these developmental stages, making disease severity highly dependent upon time of assessment.  LBD severity on flag leaves of the spring wheat variety ‘Bjarne’ at two different locations in 2010 varied during the above BBCH stages from 27% to 44% and from 4.45% to 23.2%. Different varieties may compensate differently for loss of photosynthetic area on the flag leaf due to leaf blotch pathogens, rendering the general guide line for yield loss inaccurate.  Preliminary studies in Norway indicated that the relation between yield reduction (TKW) and disease severity of the flag leaf differed substantially for five different spring varieties and ranged from 0.03 to 1.4 at BBCH 70 and from 0.8 to 4.1 at BBCH 75, at one field site at Aas, Norway in 2010. The causes of the observed variation in the relationship between flag leaf severity and yield reduction are poorly understood. Effects of other diseases are not accounted for by leaf blotch assessments, nor are fungicides applied to reference plots necessarily eliminating all disease effects on yield. Timing of assessments may be as critical as the accuracy of the assessments; making it necessary to time the assessments properly, and distinguish clearly between leaf senescence and leaf blotch symptoms.

Sammendrag

Potensiell avlingsreduksjon pga ugras, skadedyr og plantesykdommer ligger på hhv 34%, 18% og 16%. En så stor potensiell tapspost krever godt plantevern. Hvilke skadegjørere vi vil få et økt problem med og hvilke som vil bli redusert pga endret klima, er det viktig å få en oversikt over slik at tilpassede planteverntiltak kan utvikles. Klimatilpasningskompetansen til rådgiving og bønder må bygges opp gradvis. Forskningen må starte nå.

Sammendrag

The leaf blotch disease complex (LBD) frequently reduces yield of wheat in Norway. In visual assessments field symptoms can be difficult to attribute definitively to specific causal agents, and may be caused by any or all of the following three pathogens: Stagonospora nodorum (teleomorph: Phaeosphaeria nodorum) causing Stagonospora nodorum or glume blotch (SNB), Septoria tritici (teleomorph: Mycosphaerella graminicola) causing Septoria tritici or speckled leaf blotch (STB), and Drechslera tritici-repentis (teleomorph: Pyrenophora tritici-repentis) causing tan spot (DTR). There is no broad resistance to all three pathogens in commercially relevant wheat  varieties. We analyzed 9 years of historical data on severity of LBD in the field and 36 years of historical data on post-harvest SNB infection of wheat kernels. Overall, correlation between leaf severity and seed severity over years was low (r=0.5). However, during the last 4 years correlations between SNB seed infection and severity of LBD increased (r=0.825). LBD severity varied signficantly with geographic location and increased exponentially on the last 3 leaves betweeen BBCH stage 70 and the last assessment at BBCH stage 89. An improved understanding of environmental and host developmental factors as they affect each member fo the LBD complex in the field will be essential to screening for quantitative and durable resistance to LBD.

Sammendrag

Severity of leaf blotch epidemics varies annually and locally. Disease assessments between Z70 and Z85 are highly variable due to exponential increase of severity and do not consistently predict impact on yield quality and quantity

Sammendrag

The leaf blotch complex is one of the most important yield limiting disease on wheat in Norway. It is caused by three pathogens, Septoria tritici ( Mycosphaerella graminicola), Stagonospora nodorum ( Phaeosphaeria nodorum), and Drechslera tritici-repentis (Pyrenophora tritici-repentis). The symptoms of each of the pathogens are similar and easily confused with leaf senescence, making it difficult to assess the true disease severity and thus hampering breeding for leaf blotch resistance. To reduce unnecessary pesticide use and the risk of pesticide resistance developing in the fungal populations, timing of disease control measures are based on forecasting models. The degree of a leaf blotch epidemic is determined by initial inoculums, precipitation, temperature, time, availability of susceptible hosts and the degree of susceptibility. During the last 20 years, the start of the growing season as marked by a soil temperature of 5C, has advanced by 1-1.5 days per year (Rafoss, 2009), indicating an increase in the length of growing seasons. The trend for warmer and wetter growing seasons is predicted to continue in the future. It is of high relevance to the wheat industry to understand the impact of these changes on leaf blotch diseases in the field to optimize disease forecasting and management. We have collected data on leaf blotch severity in the field and weather conditions at different wheat growing areas in Norway over the last 10 years. Based on this data, we do not see a general increase in disease severity over the last decade. However, the data shows that there are local shifts in maximum disease severity; areas that support high disease severity and areas that support very little. Given the amount of initial inoculum and availability of susceptible hosts are comparable between the different wheat growing areas, the local climate per site becomes the determining factor for the epidemic.  We studied the effect of relatively small, local differences in precipitation, temperature, and start of growing season on leaf blotch development in the field. The analysis of local shifts in climatic conditions and their relation to disease development allows us to estimate the effect of the changing climate on leaf blotch disease in the future.

Project image
Bladsjukdommer i norsk hvete


Vi har sett en alarmerende skift i balansen av sopp patogene i de siste 3 årene. Bladsjukdommer kan redusere hveteavlinger betydelig. Soppsjukdommer på hveteblader inkluderer hveteaksprikk, hvetebladprikk, hvetebrunflekk, mjøldogg, og i de siste årene, gulrust. Vi har dokumentert at hveteaksprikk har vært den dominerende arten på hveteblader fra 2005 til 2014, men vi vet fra andre europeiske land at dominerende sopparter kan skifte raskt over tid. Hveteaksprikk har forsvunnet fra Sverige, Danmark, Tyskland og Stortbritania i løpet av de siste 20 år og ble erstattet av hvetebladprikk. Ulike sopper behøver ulike tiltak.  Med hensyn til optimal bruk av plantevernmidler og resistensforedling er det avgjørende å vite hvilke sopparter vi har og hvilke arter vi kan forvente i framtiden. Vi ønsker å gjennomføre en systematisk kartlegging av de ulike sopparter på høst- og vårhveteblader over to år. Samtidig skal vi sammenstille ulike dyrkningsfaktorer som jordtype, hvetesort, jordarbeiding og næringsstoffnivå av planter fra de samme åkrene for å bestemme mulige faktorer som kan påvirke hvilke bladsjukdommer vi kan forvente i framtidig hvetedyrking. Basert på resultatene skal vi utvikle anbefalinger for optimale dyrkningsstrategier for ulike områder.

Active Updated: 11.01.2017
End: des 2018
Start: jan 2017