Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
2011
Forfattere
Ricardo Holgado Christer MagnussonSammendrag
Cyst nematodes, Heterodera spp. are known world-wide as parasites of cereals and grasses. Norwegian surveys have revealed that nematodes belonging to the H. avenae complex occur throughout the country; our studies have combined morphology, protein variability (IEF), bio-tests and internal transcribed spacers (ITS3 and ITS5) for the identification of Heterodera populations. Our results showed some divergences between techniques in species identity of some of the studied populations H. avenae is the most common species followed by H. filipjevi (Holgado et al., 2009).. Several populations of H. filipjevi west did not reproduce in oat differentials. In this case both the morphology and protein patterns rather indicated these populations to belong to H. pratensis. In this study a population from Brekstad differed from all other populations in its morphology, and the protein pattern was close to H. mani. This population was collected from barley, and in the pathotype test it was virulent on several barley cultivars. Mathews, 1971reported that H. mani did not reproduce on cereals while (Cook, 1982) indicates that some barley cultivars can serve as hosts. Surprisingly the ITS studies indicated the Brekstad population to be close to H. avenae. This population is in many ways strikingly different from H. avenae, and this result may indicate a need to revise the present gene library of H. avenae. It also demonstrates the need for using several techniques in species identification. In our study the least degree of divergent results on nematode identity is between morphology and IEF.
Forfattere
Ricardo HolgadoSammendrag
Cyst nematodes, Heterodera spp. are known world-wide as parasites of cereals and grasses. Norwegian surveys have revealed that nematodes belonging to the H. avenae complex occur throughout the country; our studies have combined morphology, protein variability (IEF), bio-tests and internal transcribed spacers (ITS3 and ITS5) for the identification of Heterodera populations. Our results showed some divergences between techniques in species identity of some of the studied populations H. avenae is the most common species followed by H. filipjevi (Holgado et al., 2009).. Several populations of H. filipjevi west did not reproduce in oat differentials. In this case both the morphology and protein patterns rather indicated these populations to belong to H. pratensis. In this study a population from Brekstad differed from all other populations in its morphology, and the protein pattern was close to H. mani. This population was collected from barley, and in the pathotype test it was virulent on several barley cultivars. Mathews, 1971reported that H. mani did not reproduce on cereals while (Cook, 1982) indicates that some barley cultivars can serve as hosts. Surprisingly the ITS studies indicated the Brekstad population to be close to H. avenae. This population is in many ways strikingly different from H. avenae, and this result may indicate a need to revise the present gene library of H. avenae. It also demonstrates the need for using several techniques in species identification. In our study the least degree of divergent results on nematode identity is between morphology and IEF.
Forfattere
Christer MagnussonSammendrag
Det er ikke registrert sammendrag
Forfattere
Christer MagnussonSammendrag
Nematodes, commonly known as round worms, are the most common multicellular animals on planet Earth. After 1000 million years of evolution members of the phylum Nematoda have a high bionomic diversity. As habitants of the soil and rhizosphere nematodes are involved en energy fluxes, and affect carbon and nutrient cycles. As plant parasites, either alone or in synergism with other pathogens, nematodes are responsible for plant disease complexes and major crop losses. A growth depression in a field of potato (Solanum tuberosum) cv. Saturna [resistant to pathotype Ro1 of potato cyst nematode (PCN) Globodera rostochiensis], suggestive of potato cyst nematode damage, was detected in Grue, eastern Norway. Analyses of soil samples did not detect PCN, but demonstrated the occurrence of a large number of lesion nematodes Pratylenchus penetrans .Tubers from the depressed part of the field had severe symptoms similar to those caused by the common scab bacterium Streptomyces scabies. Potato yield was reduced by 50% in the affected area of the field. Transect-sampling showed plant growth to be negatively correlated with densities of P. penetrans and suggested a damage threshold of potato to the nematode of 100 specimens per250 g of soil. Common scab (Streptomyces scabies) occurred frequently in the affected area. P. penetrans was present in roots, underground stems, stolons and tubers. Tubers from the depressed part of the field had severe symptoms similar to those caused by the common scab bacterium. In tubers, nematodes were detected inside cross-lesions typical symptoms of common scab, and occurred also in the outermost 0.5 mm tissue associated with such lesions. In pots with sterile sand, micro-tubers of potato cv. Saturna, produced from meristems, were grown in a green-house infected with, P. penetrans, S. scabies, and a combination of P. penetrans and, S. scabies. P. penetrans alone induced tuber lesions similar to those of common scab. Also, the combined inoculation of the bacterium and the nematode seemed to enhance symptom expression. Similar scab symptoms, in connection with lesion nematode infections, have been observed on potato tubers cv. Oleva, which also is relatively tolerant to common scab. Symptomatic tubers cv. Saturna first stored at 4o C for 20 weeks were transferred to pots with sterile sand and grown for 3 months in the green-house. In these cultures P. penetrans was first detected in soil 8 weeks after planting. Examination at harvest of soil, roots, stolons, tubers demonstrated symptoms typical of P. penetrans. Interestingly, P. penetrans survives storage of potatoes, from which new infections may develop. Hence, potato tubers do appear to be an important means for the spread of P. penetrans to new areas. The fact that the symptoms induced by this nematode may be mistaken for symptoms of common scab suggests that the frequency of S. scabies might have been overestimated in regular surveys. Infections by P. penetrans have important implications for scab control. This pertains in particular to recommended maintenance of high soil moisture at and during 4-9 weeks after tuber set. If symptoms are related to nematode infection rather than to the scab bacterium, this recommendation would allow for a rapid build-up of lesion nematodes resulting in a decrease in both yield and marketability of the tubers. Further studies are needed to investigate the extent of this problem.
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Christer Magnusson Ricardo HolgadoSammendrag
Some species of plant parasitic nematodes restrict severely the productivity of crops. In Nordic countries nematodes are often overlooked as factors explaining crop failure. This neglect may relate to a 2/3 reduction of personnel in Nordic nematology which has happened since 1994. The resulting decrease in the lecturing and training of students threatens recruitment, scientific development and awareness of plant nematodes as parasites. This is serious since damage from nematodes can only be reduced by correct management of populations. This will contribute to soil health and a sustainable production. Potato cyst nematode (PCN), Globodera spp., is economically the most important pest attacking potato. It is difficult to detect in the fields, and 20 years may elapse before damage is noticed. The cost for managing PCN is high since management relies on intensive monitoring and regulation. PCN is mainly managed by crop rotations with non-hosts crops grown between alternating susceptible and resistant potato. Among cereal cyst nematodes (CCN) the most common species are Heterodera.avenae and H. filipjevi. Both species have pathotypes differing in their host preferences. Under Nordic conditions serious damage seems to appear with about 40-years intervals. For CCN, correct knowledge of species, pathotype and population density is essential in designing crop rotations. Optimal rotations may allow for yield increases of up to 1 t/ha. In Norway and Sweden damage from root knot nematodes (RKN), Meloidogyne hapla on vegetables and M. naasi on cereals, has been detected more frequently in recent years. RKN have their largest importance in continental and southern Europe, and the increase in field damage seen in the Nordic area may be a first sign of climate change. It is likely that also damage from other nematodes will increase with rising temperatures. Research cooperation between Nordic countries seems urgent to meet the future challenges in plant nematology.
Forfattere
Christer MagnussonSammendrag
The capacity for research and services in Plant Nematology has decreased much in the last 20 years. This is happening world wide and in the Nordic region the staff in Nematology has been reduced by 2/3 since 1994. We have already entered a situation where the capacity in most countries is insufficient to meet actual needs for research and development, as well as the needs for diagnostic services. Today the critical mass of the Nordic region is dangerously low. The scientific support required in decision making demonstrates a need to ensure the engagement of a sufficient number of nematologists. The present decrease in lecturing and training activities threatens recruitment and development. This situation can only be solved by an increase in research collaboration between Nordic countries.
Forfattere
Christer MagnussonSammendrag
Det er ikke registrert sammendrag
Forfattere
Ricardo HolgadoSammendrag
Studier av Potetcystenematoder (PCN) i nordlige områder Prosjektet skal forbedre bekjempelsen av potetcystenematoder (PCN). Dette skal oppnås ved å skaffe mer kunnskap om de ulike patotypene, populasjonsutvikling, nedgang av smitte når det ikke dyrkes poteter på arealet, eventuelle parasitter og utbredelsen av resistens i ulike potetsorter. Potetcystenematoder (PCN) har stor økonomisk betydning. Både den gule arten (yPCN), G. rostochiensis, og den hvite arten (wPCN), G. pallida, er karanteneskadegjørere og reguleres i Matloven. I Norge legges arealer infisert med wPCN eller virulente raser av yPCN i karantene på 40 år bl.a. med forbud mot dyrking av potet, produksjon av planter til videre dyrking og bortføring av jord. Prosjektets hovedmål er å forbedre den fremtidlige bekjempelsen av PCN ved å: (a) klarlegge patotypespekter i utvalgte populasjoner, (b) klarlegge smittenedgang og infeksjonspotensial i fravær av vertsplanter, (c) Initiere studier av forekomst og patogenitet til parasittære mikroorganismer på PCN, (d) studere populasjonsnedgang i felt med tidlig potet og Solanum sisymbriifolium og (e) undersøke resistens- og toleranse for PCN i potetsorter, (f) Initiere studier av pathosystemet (PCN-potet). Målet er å forbedre bekjempelsen av PCN og vurdere å åpne for kortere karanteneperiode. Ny kunnskap vil øke effektiviteten i norsk potetproduksjon. Identiteten til valgte populasjoner av PCN dokumenteres med mikroskopi, iso-elektrisk fokusering og DNAbaserte teknikker som PCR og RFLP. Patotypetest gjennomføres ved JKI Tyskland og ved Bioforsk Plantehelse (a). Smittenedgang i bestemt felt studeres på arealer som er karantenelagt siden 1955. Egg i PCN-cyster gjennomgår her klekketest og klekte juvenilers infeksjonsdyktighet og nematodenes reproduksjon undersøkes på mottakelig potet (b). Preliminære studier av forekomst og patogenitet hos parasittære mikroorganismer på PCN, samt identifikasjon og kvantifisering av mikroorganismer basert på molekylære metoder som qrt-PCR, DGGE i samarbeid med JKI Tyskland (c). I feltforsøk i Nord Trøndelag, Rogaland, østfold og Vestfold, undersøkes betydningen av tidligpotet og Solanum sisymbriifolium for saneringen av PCN (d). Kartlegging av resistens –og toleranse hos norske noen markedssorter av potet undersøkes med PCN populasjoner av kjent art og patotype (e). Initialstudier av pathosystem- nematode/plante-interaksjon (proteomics) ved hjelp av molekylære metoder, gjennomføres ved Universidad Autonoma de Madrid Spania i samarbeid med Bioforsk Plantehelse (f).
Forfattere
Ricardo HolgadoSammendrag
mest avanserte og fremgangsrike planteparasitter. PCN ble påvist i Europa av Kühn i 1881, og i 1923 erklærer Wollenweber den som egen art. Stone i 1973 skiller PCN i to arter. Gul PCN (Globodera rostochiensis) og hvit PCN (G. pallida). I Norge ble PCN først påvist 1955 i Agderfylkene. PCN har spredt seg raskt og i1993 ble de første funn gjort i Nord-Trøndelag. På verdensbasis er PCN funnet utbredt i 23 land og har en begrenset forekomst i 42 land, og i tillegg er det 130 land det ikke er blitt påvist enda. Både gul og hvit PCN er klassifisert som karanteneskadegjørere i 106 respektive 55 land. I de siste årene har PCN blitt påvist i Australia, Canada og USA, som på nytt satt fokus på hvor lett PCN kan spres og hvilke nasjonale konsekvenser PCN har. De plantesanitære og økonomiske konsekvensene av PCN er betydende. I EU vil PCN bli regulert i det nye EU direktivet 2007/33/EC som implementeres nå. Formålet med direktivet er å bergrense og kontrollere spredningen til PCN. I direktivet gjøres det ingen forskjell mellom gul og hvit PCN, det nevnes at arealer for settepotet og planter til videre dyrking må ha en offisiell dokumentasjon om PCN status, det skal årlig gjennomføres offisiell prøvetaking av 0,5 % av arealet av felt for produksjon av annen potet enn settepotet. Smittede felt får ikke brukes til produksjon av settepotet eller planter til videre dyrking. Bekjempelsestiltak iverksettes på smittede felt som skal brukes til produksjon av annen potet enn settepotet. Ved resistensbryting skal PCN populasjonen rasetestes. Det skal sendes en årsrapport til EU om tiltak som iverksettes i hvert land. I dag benyttes nematicider for å kontrollere PCN, og samtidig disponeres mye resurser for å foredle sorter med resistens.