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.
2009
Sammendrag
Crown rot caused by Phytophthora cactorum is an important disease in commercial strawberry production worldwide. The level of resistance varies greatly between cultivars, and many of the most commonly grown cultivars are quite susceptible to P. cactorum. Adequate soil drainage, clean planting material and use of highly resistant cultivars are the most important measures against crown rot. Previous work at our institute has involved evaluation of methods to screen for resistance, cultivar and progeny screening, and use of induced resistance against the disease. That work also included a genetic study of P. cactorum isolates from various host plants and different geographic origins. P. cactorum has many host plants, but it turned out that isolates causing crown rot of strawberry differs genetically from those with other host origin. A project was recently initiated, where one of the main goals has been to identify molecular markers for resistance against P. cactorum in strawberry. Genotypes of diploid Fragaria species have been screened for resistance, and the progeny from a cross between a susceptible and a resistant genotype will be evaluated by the end of this year. Commercially grown strawberry is very heterozygous and octoploid. Diploid Fragaria species are therefore useful as model organisms. The Fragaria genus has a conserved organisation, and hopefully information obtained from the study of diploid genotypes can be transferred to cultivated Fragaria x ananassa and possibly to other important crop plants in Rosaceae.
Sammendrag
Red stele in strawberry is caused by the oomycete Phytophthora fragariae. To prevent the introduction of the pathogen to Norway, it has been prohibited to import planting material of Fragaria spp. to the country since 1986. During 1995 to 1997 the Food Authority had a country-wide survey to reveal if P. fragariae was present. The pathogen was found in three separate regions: (i) Hedmark County, along the Mjøsa lake; (ii) Aust-Agder and Vest-Agder Counties, in coastal areas; (iii) Rogaland and Hordaland Counties, along the western border between the two counties. In the latter area there were clear indications of spread of infected plant material from a small certified nursery where P. fragariae was detected. All strawberry farms that had received plants from the nursery were thoroughly investigated and further sales of planting material was stopped. All other incidences in the 1995-97 survey were among strawberry fruit producers. In 2006 and 2007 there were two new detections of red stele in Vest-Agder, and one of the growers had produced and forwarded non-certified planting material to other strawberry growers. In 2008, a new country-wide survey was initiated, and the pathogen was found at a few new production sites for strawberry fruits in Hedmark and at one site in Vestfold County (in south eastern Norway). In 2009, red stele was also discovered at one site in Møre og Romsdal County (in western Norway). Totally, red stele has been found at 19 production sites in Norway. Since the mid 1990"s there have been no discoveries of red stele among certified plant producers. Sites where P. fragariae has been detected may continue to produce strawberry fruit for sale, but all production of strawberry plants or other planting material for further distribution is prohibited. For strawberry production on soil infested with P. fragariae, buffer zones to neighboring fields and creeks/rivers are required. No strawberry production can take place in the buffer zones, and normally the zones should be at least 100 m wide, but topographic and other conditions locally may increase or decrease the width of the zones. There are also restrictions on sharing machinery and equipment with other farms, and soil from infested farms may not be moved out of the farm. Testing of plant material is done by a root tip bait test and PCR.
Forfattere
Belachew Asalf Arne Stensvand David M. Gadoury Robert C. Seem Andrew Dobson Anne Marte TronsmoSammendrag
Development of ontogenic resistance to powdery mildew (Podosphaera aphanis) in strawberry fruit has not been quantified, and thus cannot be exploited in disease management programs. Four commercially-relevant strawberry cultivars were evaluated for ontogenic resistance to powdery mildew. Fruits were inoculated at one of the four growth stages: flowering, green, white and early pink fruit. There was a significant difference between and within cultivars at the bloom and green stage of inoculations (P ≤ 0.05) for both disease incidence and severity. On average 16.4, 39.5, 48.7, and 60.3 % of the fruits inoculated at bloom developed powdery mildew in cultivars Elan, Korona, Frida and Inga, respectively. None of the cultivars developed powdery mildew when inoculated at the pink stage. It may be concluded that flowers and green fruits of strawberry were much more susceptible to powdery mildew infection than white and pink fruits. The high susceptibility of cultivars at the flower and early green stages seemed coincident with the succulent nature of the fruits at these stages, making it easy for penetration and establishment of mildew. Control measures targeting at these critical windows of fruit susceptibility are likely to reduce yield loss.
Forfattere
Robert C. Seem Arne Stensvand David M. Gadoury Håvard Eikemo Andrew Dobson M. Catherine HeidenreichSammendrag
The objective of this work was to investigate how primary disease levels of powdery mildew (Podosphaera aphanis) in strawberry (Fragaria × ananassa) influence disease development in time and space. Experiments were repeated over two seasons in field trials in Norway (Ås, cv. Korona) and USA (Geneva, NewYork, cvs. Earliglow and Elan). Five-row plots of 50 to 100 mildew-free plants (planting distance 0.45 x 1.2 m) were established each year within large grain fields, with a minimum distance of 90 m between plots, and no fungicide treatments. At start of the experiments, plants at the center of each plot were inoculated with 0, 1, 10, or 100 mildew-infected leaflets. Uninoculated plots developed only trace levels of powdery mildew, despite nearby diseased plots. More rapid and severe disease development was observed in the inoculated plots; e.g., mildew was observed on 31, 36, 311, and 912 leaflets in the 0, 1, 10, and 100 plots, respectively, in Norway in year 1 of the trial. Within the plots, disease development was highest close to the inoculum source and downwind from the prevailing wind. It may be concluded that in the absence of nearby sources of contamination, disease severity in strawberry plantings is determined by the dose of initial inoculum resident within the planting. The practical impact of the trials was to demonstrate long-lasting benefits of clean, mildew-free planting stock in commercial strawberry production, even in areas where the pathogen is endemic and the environment is very conducive to disease.
Sammendrag
Results from the study "Effects of metabolic changes during cold hardening on freezing survival of Agrostis spp." were presented. The objectives of the trial were: (1) to compare freezing tolerance of velvet bentgrass and creeping bentgrass, (2) to quantify carbohydrate and protein changes during the two consecutive phases of cold acclimation in these species, and (3) to compare one direct and two indirect methods for determination of LT50 in turfgrasses. Four treatments representing different phases of cold acclimation were compared: (i) non-acclimated (NA) plants maintained at 18 / 12 °C (day/night); (ii) plants acclimated at 2 °C for 2 wk (A2); (iii) plants acclimated at 2 °C for 4 wk (A4); and (iv) plants acclimated at 2 °C for 4 wk with an additional sub-zero acclimation in the dark at -2 °C for 2 wk (A4+SZA2). Velvet bentgrass and creeping bentgrass showed no difference in lethal temperatures for 50% of the test population (LT50) as estimated by whole plant survival. Treatments A2 and A4 resulted in accumulation of sucrose and fructans, and significantly lowered LT50 as compared with NA. A4+SZA2 resulted in less fructans, no difference in sucrose and higher concentration of reducing sugars but LT50 was not lower than after A4 treatment. Crown viability determined by reduction of tetrazolium chloride showed close correlation with LT50 values based on whole plant survival. Electrolyte leakage produced less consistent results and cannot be recommend as a quick method for evaluation of relative hardiness of the rather small crowns of bentgrass species, especially not if acclimation at subfreezing temperatures is part of the testing procedure.
Forfattere
Tatsiana EspevigSammendrag
Preliminary results from the study "Effects of metabolic changes during cold hardening on freezing survival of Agrostis spp." were presented. The objectives of the trial were: (1) to compare freezing tolerance of velvet bentgrass and creeping bentgrass, (2) to quantify carbohydrate and protein changes during the two consecutive phases of cold acclimation in these species, and (3) to compare one direct and two indirect methods for determination of LT50 in turfgrasses. Three (of four) treatments representing different phases of cold acclimation were compared: (i) nonacclimated (NA) plants maintained at 18 °C/12 °C (day/night); (ii) plants acclimated at 2 °C for 2 wk and 250 μmol m-2 s-1 for 12 h photoperiod (A2); and (iii) as treatment (ii) but for 4 wk (A4). Plants exposed to additional sub-zero acclimation in the dark at -2 °C for 2 wk (A4+SZA2) were under acclimation treatment at that time. Results regarding 1st and 3rd objectives were discussed. Acclimation at 2 ºC significantly improved freezing tolerance of both species, but differences between species were not significant. The LT50 for plants subjected to A2 and A4 were 4 and 6 °C lower, respectively, compared to NA plants. Crown viability test had a good correlation with the LT50 based on whole plant survival. Electrolyte leakage underestimated freezing survival ability in Agrostis spp.
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Tatsiana EspevigSammendrag
One of the major concerns for the use of velvet bentgrass (Agrostis canina) in Scandinavia is whether current cultivars have sufficient winter hardiness. To meet this challenge, velvet bentgrass (VB) cultivars were tested for winter hardiness in controlled environments at UMB during 2006/2007. Hardened and unhardened VB cultivars Avalon, Villa, Greenwich and Legendary were compared with creeping bentgrass (CB, Agrostis stolonifera) cv. Penn A-4 (control) for freezing tolerance. There were no differences in freezing tolerance between velvet and creeping bentgrass, but none of the tested cultivars, whether hardened or not, tolerated freezing to - 9 ºC or lower.That became a background for the collaborative project between the Norwegian Institute of Agricultural and Environmental Research (Bioforsk), Norwegian University of Life Science, Rutgers University and the University of Massachusetts. The objectives of the project would be: (1) to compare freezing tolerance of VB and CB, (2) to quantify carbohydrate changes during the two consecutive phases of cold acclimation in these species, and (3) to compare one direct and two indirect methods for determination of LT50 in turfgrasses.
Forfattere
Nils VagstadSammendrag
Det er ikke registrert sammendrag
Sammendrag
Forsøk med oppfôring av kopplam etter to ulike strategier viser at produksjon av kopplam med bruk av melkeerstatning og kraftfôr generelt er lite lønnsomt. Det er beregnet et forventet "overskudd" per kopplam på bakgrunn av utgifter til melkeerstatning og kraftfôr de første syv ukene (tabell 1) og utgiftene til kraftfôr i beiteperioden fram til slakt. "Overskuddet" er beregnet til ca 173 kr og 53 kr hhv i 2007 og 2008. Det er i beregningene ikke tatt hensyn til alle utgifter som vaksiner, smokker, flasker, strø og arbeid. Det kan være aktuelt å se på andre former for framfôring som for eksempel en mer moderat tildeling av kraftfôr i beiteperioden (400-500 g per dyr per dag) og eventuelt bruk av annen type beite enn vanlig eng. Mer forskning må til før det er mulig å konkludere med lønnsomheten i norsk kopplamproduksjon.