| 1. |
- Andersson, Annhild, et al.
(författare)
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Occurrence of aphid vector and genetic tolerance to infection by potyvirus in hot pepper
- 2010
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Ingår i: Euphytica. - : Springer Science and Business Media LLC. - 0014-2336 .- 1573-5060. ; 172, s. 77-91
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Tidskriftsartikel (refereegranskat)abstract
- The productivity and marketable quality of hot pepper (Capsicum annuum var. annuum L.) are low in tropical regions mainly due to virus infections and lack of effective virus management strategies. The absence of effective virus management strategies could be attributed to lack of information on virus vectors and host resistance. Parental (P(1) and P(2)) and progeny (F(1), B(1), B(2) and F(2)) generations of five hot pepper crosses were grown in Ethiopia at three sites (Bako, Hawasa and Melkasa) to monitor number and species of potential aphid vectors, disease incidence levels with regards to natural infections by Potato virus Y (PVY) and Ethiopian pepper mottle virus (EPMV) complex, and to determine genetic tolerance of the crop to the viruses. Disease incidence was assessed before the flowering stage of the crop plants using visible disease symptoms due to infections by PVY and EPMV. The serological tests revealed presence of symptomless genotypes of the crop to the virus infections. Aphid species potentially transmitting the viruses, such as Acyrthosiphon pisum (Harris), Aphis fabae (Scopoli), and Myzus persicae (Sulzer), were identified from specimens caught by yellow water traps. The highest number of aphids from yellow water traps was recorded at a dense foliage growth stage of the crop at Melkasa. Highly significant variation was observed among generations of the five crosses in response to infections by PVY and EPMV complex. The most susceptible parents had the levels of disease incidences ranging from 80 to 90%, whereas their progenies had only below 30% incidence levels. The most tolerant parent remained symptomless to the natural infections of PVY- and EPMV-complex. Incidence levels in progenies of a cross from the most susceptible and tolerant parents remained below 20%. Based on serological test, the proportion of PVY-positive plants ranged from 0 to 75% and of EPMV-positive plants from 0 to 25%, with 0 to 17% co-infection by the two viruses. Availability of virus sources in the vicinity, efficiency of aphids in vectoring, weather conditions during the growth period, genetic tolerance and the growth stage of the crop affected natural infection by PVY- and EPMV-complex. Exploitation of the genetic potential of introduced elite genotypes and their progenies along with breeding elite local cultivars for resistance and excluding aphid vectors at young (seedling) stage of the crop plants could be helpful for minimizing losses in yield and quality of hot pepper due to infections by PVY- and EPMV-complex.
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| 2. |
- Bommarco, Riccardo, et al.
(författare)
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Cereal aphid populations in non-crop habitats show strong density dependence
- 2007
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Ingår i: Journal of Applied Ecology. - : John Wiley & Sons. - 0021-8901 .- 1365-2664. ; 44:5, s. 1013-1022
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Tidskriftsartikel (refereegranskat)abstract
- 1.Few studies have addressed how density-dependent and density-independent regulation of population growth and abundance varies among habitats for a species that requires multiple habitat types to complete its life cycle. Understanding such relationships, however, are of direct relevance to the control of crop pest insects that regularly move between crop and non-crop habitats.2.We used autoregressive models to analyse a series of seasonal catches of the cereal aphid Rhopalosiphum padi. The data were collected from regional suction traps and egg counts on the overwintering host, over a period of 14–31 years, at four locations in Sweden. R. padi is an obligate host-alternating species in Sweden and seasonal catches reflect habitat use in a year: the primary woody host in winter and spring, the cereal crops in summer, and the perennial grasslands in the autumn.3.Strong direct density dependence acting within the year was found, but the strength varied between seasons depending on habitat use by the aphids during the year. Only a weak indication or no indication at all of density dependence was found during the period of residency on the primary host in the winter and spring periods.4.Density dependence occurred when R. padi utilized summer cereals (42% of the variation was explained), and even stronger density dependence occurred in the perennial grasslands in the autumn (70% variation explained). Stochastic fluctuations in the winter and spring were balanced by a strong density dependence in the cereal and grassland habitats in the summer and autumn periods, which reduced variability in population fluctuations.5.Weather, measured as seasonal average temperature and accumulated precipitation, did not affect aphid abundance fluctuations much, explaining only 1–9% of the variability.6.Synthesis and applications. Our results suggest that density-dependent regulation of R. padi occurs in late summer grasslands and early summer cereals. The mechanisms causing these patterns are not understood, making it difficult to provide specific pest management recommendations at this stage. The results do indicate, however, that pest management needs to involve a landscape-level approach, taking into account mechanistic information about the plant, herbivore and predator interactions in multiple habitats visited by the herbivorous pest.
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| 3. |
- Bötzl, Fabian, et al.
(författare)
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Predicting crop injury caused by flea beetles in spring oilseed rape through pest monitoring in the autumn
- 2024
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Ingår i: Agricultural and Forest Entomology. - 1461-9555 .- 1461-9563. ; 26, s. 62-69
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Tidskriftsartikel (refereegranskat)abstract
- 1. Reliably predicting pest damage would allow farmers to reduce insecticide use without incurring economic losses and thus contribute to agricultural sustainability. However, means to predict pest severity are lacking.2. We assessed whether crop feeding injury caused by flea beetles in spring oilseed rape can be predicted from flea beetle pest densities in the previous season using 22 years of suction trap catches of flea beetles in combination with crop feeding injury data from 293 fields.3. We found a strong positive relationship between the densities of flea beetles of the genus Phyllotreta in the summer and autumn activity period of the previous year and crop feeding injury caused by flea beetles in spring oilseed rape the following year. Autumn weather or the total cover of spring oilseed rape in the study region did not improve the prediction further.4. Pest monitoring using suction traps is thus a promising tool to predict crop feeding injury and can reduce insecticide use in years with low pest pressures.
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| 4. |
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| 5. |
- Emery, Sara, et al.
(författare)
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Cold winters drive consistent and spatially synchronous 8-year population cycles of cabbage stem flea beetle
- 2022
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Ingår i: Journal of Animal Ecology. - : Wiley. - 0021-8790 .- 1365-2656. ; 92, s. 594-605
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Tidskriftsartikel (refereegranskat)abstract
- 1. Population cycles have been observed in mammals as well as insects, but consistent population cycling has rarely been documented in agroecosystems and never for a beetle.2. We analysed the long term population patterns of the cabbage stem flea beetle Psylliodes chrysocephala in winter oilseed rape over 50 years.3. Psylliodes chrysocephala larval density from 3045 winter oilseed rape fields in southern Sweden showed strong 8 year population cycles in regional mean density. Fluctuations in larval density were synchronous over time across five subregional populations. Subregional mean environmental variables explained 90.6% of the synchrony in P. chrysocephala populations at the 7-11 year time-scale. The number of days below -10 degrees C showed strong anti phase coherence with larval densities in the 7-11 year time-scale, such that more cold days resulted in low larval densities. High levels of the North Atlantic Oscillation weather system are coherent and anti phase with cold weather in Scania, Sweden.4. At the field-scale, later crop planting date and more cold winter days were associated with decreased overwintering larval density. Warmer autumn temperatures, resulting in greater larval accumulated degree days early in the season, increased overwintering larval density.5. Despite variation in environmental conditions and crop management, 8 year cycles persisted for cabbage stem flea beetle throughout the 50 years of data collection. Moran effects, influenced by the North Atlantic Oscillation weather patterns, are the primary drivers of this cycle and synchronicity. Insect pest data collected in commercial agriculture fields is an abundant source of long term data. We show that an agricultural pest can have the same periodic population cycles observed in perennial and unmanaged ecosystems. This unexpected find- ing has implications for sustainable pest management in agriculture and shows the value of long term pest monitoring projects as an additional source of time series data to untangle the drivers of population cycles.
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| 6. |
- Jonsson, Mattias, et al.
(författare)
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Suction-trap catches partially predict infestations of the grain aphid Sitobion avenae in winter wheat fields
- 2016
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Ingår i: Journal of Applied Entomology. - : Wiley. - 0931-2048 .- 1439-0418. ; 140, s. 553-557
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Tidskriftsartikel (refereegranskat)abstract
- Effective pest monitoring programmes are needed for providing reliable advice on when pest populations require active management. We studied whether suction-trap catches of the grain aphid Sitobion avenae during the period 1989-2009 can be used to predict field infestations of this aphid in Swedish winter wheat fields. We found that suction-trap catches of S.avenae until the time of crop heading (GS51) were significantly related to both number of aphids per tiller (R-2=0.69 at GS 59 and R-2=0.27 at GS 69) and proportion of fields with infestations above economic threshold (R-2=0.49 at GS 59 and R-2=0.40 at GS 69). This effect was consistent across Swedish regions and years. This information could be used by advisory services and farmers to decide whether field inspection to estimate the profitability of insecticide treatment at heading is needed. To improve the predictive ability further, suction-trap catches could be combined with weather data and information about biological control potential in different landscapes.
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| 7. |
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| 8. |
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| 9. |
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| 10. |
- Sigvald, Roland
(författare)
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A diagnostic real-time PCR assay for the rapid identification of the tomato-potato psyllid, Bactericera cockerelli (Sulc, 1909) and development of a psyllid barcoding database
- 2020
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- The accurate and rapid identification of insect pests is an important step in the prevention and control of outbreaks in areas that are otherwise pest free. The potato-tomato psyllid Bactericera cockerelli (Sulc, 1909) is the main vector of 'Candidatus Liberibacter solanacearum' on potato and tomato crops in North America and New Zealand; and is considered a threat for introduction in Europe and other pest-free regions. This study describes the design and validation of the first species-specific TaqMan probe-based real-time PCR assay, targeting the ITS2 gene region of B. cockerelli. The assay detected B. cockerelli genomic DNA from adults, immatures, and eggs, with 100% accuracy. This assay also detected DNA from cloned plasmids containing the ITS2 region of B. cockerelli with 100% accuracy. The assay showed 0% false positives when tested on genomic and cloned DNA from 73 other psyllid species collected from across Europe, New Zealand, Mexico and the USA. This included 8 other species in the Bactericera genus and the main vectors of 'Candidatus Liberibacter solanacearum' worldwide. The limit of detection for this assay at optimum conditions was 0.000001ng DNA (similar to 200 copies) of ITS2 DNA which equates to around a 1:10000 dilution of DNA from one single adult specimen. This assay is the first real-time PCR based method for accurate, robust, sensitive and specific identification of B. cockerelli from all life stages. It can be used as a surveillance and monitoring tool to further study this important crop pest and to aid the prevention of outbreaks, or to prevent their spread after establishment in new areas.
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| 11. |
- Sigvald, Roland
(författare)
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Aerial psyllid (Hemiptera: Psylloidea) detection and monitoring using suction traps in Britain: population observations, new species found and a revised British checklist
- 2020
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Ingår i: Entomologists Gazette. - 0013-8894. ; 71, s. 151-163
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Tidskriftsartikel (refereegranskat)abstract
- The Psylloidea contains species that can transmit pathogens to plants, including important agricultural crops e.g. the proteobacterium 'Candidatus Liberibacter solanacearum' (CaLsol) to potatoes. To obtain a better understanding of British psyllid populations, a study was conducted over two years to determine their aerial incidence and diversity using an existing network of 12.2 m suction traps. In total, 42 species were detected in the traps. In 2015 in England, the most common species was the grouping of Cacopsylla melanoneura and C. affinis followed by Trioza remota (the latter being most prevalent in autumn). In contrast, in Scotland Cacopsylla species (melanoneura, affinis, pulchra and brunneipennis) accounted for 81% of the population in spring and summer. The yearly sampling in England in 2015 revealed that the aerial movement of the most common species differed in their phenology. The grouping of Cacopsylla melanoneura and C. affinis, as well as T. urticae were most common in summer whereas T. remota was most prevalent in late autumn. Three species new to Britain: Cacopsylla alaterni, Trioza anthrisci and Ctenarytaina spatulata were caught during sampling, in addition to Trioza apicalis which transmits CaLsol. Following our study, the British psyllid checklist was revised and is presented here. The potential of suction traps for monitoring and detecting psyllid species was demonstrated in Britain and confirmed by a limited assessment of catches from a Swedish trap in which two species not present in Britain were found. These were Trioza tatrensis and Trioza dispar.
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| 12. |
- Sigvald, Roland
(författare)
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Aktuellt om bladlöss i stråsäd
- 2011
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Ingår i: Växtskyddsprognoser från SLU. - 1402-7623.
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Annan publikation (populärvet., debatt m.m.)
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| 13. |
- Sigvald, Roland
(författare)
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Assessment of the impact of climate change on the latency period of leaf rust on triticale in Poland
- 2020
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Ingår i: Acta Agriculturae Scandinavica, Section B - Soil and Plant Science. - : Informa UK Limited. - 0906-4710 .- 1651-1913. ; 70, s. 195-207
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Tidskriftsartikel (refereegranskat)abstract
- Disease development in plants is strongly dependent on weather conditions, with temperature playing a particularly significant role by influencing latency period duration. Using two models describing the relationship between latency period and temperature, we performed simulations aimed at predicting changes in the latency period of leaf rust (Puccina recondita f. sp. tritici) on triticale in response to expected climate change. The simulations were based on meteorological data recorded in the period 1986-2005 at locations representing 16 provinces in Poland and based on values obtained after transformation of the observed data to reflect temperature changes under four scenarios (RCP2.6, RCP4.5, RCP6.0 and RCP8.5) according to the giss_e2_r climate model. In all scenarios, the results for the two triticale cultivars studied, Witon (vulnerable to P. recondita) and Gniewko (less susceptible), showed a threat of faster development (shorter leaf rust latency period) on triticale triggered by climate change in south-east and south-central Poland than in other regions. The results also showed an increased probability of future regional diversification of leaf rust latency period duration on vulnerable triticale cultivars, opportunities for earlier start of leaf rust epidemics on triticale in Poland and an increase in ?nal disease severity in comparison with 1986-2005.
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| 14. |
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| 15. |
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| 16. |
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| 17. |
- Sigvald, Roland
(författare)
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Forecasting the influence of temperature increase on the development of the Colorado potato beetle [Leptinotarsa decemlineata (Say)] in the Wielkopolska region of Poland
- 2013
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Ingår i: Acta Agriculturae Scandinavica, Section B - Soil and Plant Science. - : Informa UK Limited. - 0906-4710 .- 1651-1913. ; 63, s. 136-146
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Tidskriftsartikel (refereegranskat)abstract
- The Colorado potato beetle (Leptinotarsa decemlineata) is probably the most dangerous pest species of potatoes. This study assessed the influence of expected climate warming on the number of Colorado potato beetle generations in the Wielkopolska region of Poland using two simulation models, SimLep 1 and NumoGen 1. Two types of data sets were utilised in the simulations: real meteorological data recorded in Winna Gora (52.2N; 17.4E) in the period 20022011 and virtual data obtained after transformation of the real data to include an increase in the recorded temperature values between 1 and 6 degrees C. The threat to potato crops from Colorado potato beetle was found to increase in response to expected climate change. A temperature increase of 2 degrees C above that recorded during the last few years would allow the development of two full generations of the beetle, and further temperature increases may even permit the occurrence of three generations.
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| 18. |
- Sigvald, Roland
(författare)
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Genetic analysis for some plant and fruit traits, and its implication for a breeding program of hot pepper (Capsicum annuum var. annuum L.)
- 2009
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Ingår i: Hereditas. - : Springer Science and Business Media LLC. - 0018-0661 .- 1601-5223. ; 146, s. 131-140
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Tidskriftsartikel (refereegranskat)abstract
- Two separate field experiments were conducted on hot pepper in which the genetic, heritability and environmental components of variation for seven plant and fruit traits in 78 genotypes and gene effects for four fruit traits in six generations of five crosses were estimated. The objectives were to determine the variation and effects of genes controlling inheritance of plant and fruit traits, and to propose efficient breeding procedures for improving the crop. Analysis of variance in half-diallel crosses revealed the presence of total genetic variability for seven traits among the 78 experimental entries with an excess of over-dominance genes. The presence of unequal distributions of dominant genes with positive and negative effects was observed among the parents and indicated the need to be cautious while selecting hot pepper parents for breeding purposes. Significant variability was also revealed in environmental sensitivity among the 78 experimental entries for some traits along with high heritability, which could be an advantage for a plant breeder but provides less clear opportunities for an agronomist to achieve better plant and fruit traits. Progeny generations (F(1), F(2), B(1) and B(2)) were found to perform better for fruit traits than their parents (P(1) and P(2)). The presence of significant gene interactions indicated a polygenic inheritance of the fruit traits studied and the possibility of pyramiding favorable alleles in the required directions at different levels of progeny generations. Heterosis, backcrossing, multiple crossing and pedigree breeding methods with recurrent selection may facilitate simultaneous exploitation of the genetic components and gene effects obtained. Nevertheless, it is doubtful whether selection efforts within the current set of hot pepper parents would be beneficial to achieve superior fruit traits for developing new varieties.
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| 19. |
- Sigvald, Roland
(författare)
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Heterosis and heritability in crosses among Asian and Ethiopian parents of hot pepper genotypes
- 2009
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Ingår i: Euphytica. - : Springer Science and Business Media LLC. - 0014-2336 .- 1573-5060. ; 168, s. 235-247
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Tidskriftsartikel (refereegranskat)abstract
- Hot pepper is the most important worldwide grown and consumed spice and vegetable crop. Though hybrid breeding has been proposed for genetic improvement in the crop, but there is lack of information on heterosis in crosses among crop genotypes in Ethiopia. Twelve genotypes (nine Asian and three Ethiopian parents) of hot pepper were crossed in 2003 cropping season in a half-diallel fashion to fit Griffing's fixed effect model analysis. An open field experiment was conducted in 2004/2005 to investigate heterosis for fourteen traits in 66 F(1) hybrids grown together with their 12 selfed parents. Highly significant genotypic differences were observed for all the traits except for leaf area. Variance component due to specific combining ability (dominance) were larger than that due to general combining ability (additive) for each of the studied traits with few exceptions. Broad sense heritability (H (b) (2) ) for fruit traits were more than 60% and with wide gap from narrow sense heritability (h (n) (2) ) for most of the important traits like number of fruit per plant (H (b) (2) = 88.3% and h (n) (2) = 46.0%), days to maturity (H (b) (2) = 87.2% and h (n) (2) = 23.1%) and dry fruit yield per plant (H (b) (2) = 72.6% and h (n) (2) = 14.6%). Maximum heterosis over mid-parent and better-parent, and economic superiority of hybrid over standard check were recorded, respectively for dry fruit yield per plant (163.8, 161.8 and 92.1%), number of fruits per plant (104.4, 79.6 and 136.4%) and days to maturity (-29.8, -31.5 and -23.6%). These observations suggested a possibility of utilizing dominance genetic potentiality available in diverse genotypes of the crop by heterosis breeding for improving hot pepper to the extent of better economic return compared to the current commercial cultivar under production in the country. Low narrow sense versus very high broad sense heritability for days to maturity and dry fruit yield per plant could be a sign for achievability of earliness and high fruit yield using heterosis in hot pepper. The maximum heterobeltiosis were recorded either from F(1)s obtained from Ethiopian and Asian crosses or from within Asian crosses, suggesting the possibility of maximizing heterosis by considering genetically diverse parental genotypes. The manifestation of highest heterosis in hybrids from among Asian lines indicated existence of genetic diversity among Asian genotypes and the potentiality for improvement of hot pepper using genotypes from different regions of the world along with elite inbred lines from local cultivars.
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| 20. |
- Sigvald, Roland, et al.
(författare)
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Molecular identification of bloodmeals and species composition in Culicoides biting midges
- 2013
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Ingår i: Medical and Veterinary Entomology. - : Wiley. - 0269-283X .- 1365-2915. ; 27, s. 104-112
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Tidskriftsartikel (refereegranskat)abstract
- Investigations of host preferences in haematophagous insects, including Culicoides biting midges (Diptera: Ceratopogonidae), are critical in order to assess transmission routes of vector-borne diseases. In this study, we collected and morphologically identified 164 blood-engorged Culicoides females caught in both light traps and permanent 12-m high suction traps during 20082010 in Sweden. Molecular analysis of the mitochondrial cytochrome c oxidase subunit I (COI) gene in the biting midges was performed to verify species classification, discern phylogenetic relationships and uncover possible cryptic species. Bloodmeal analysis using universal vertebrate cytochrome b primers revealed a clear distinction in host selection between mammalophilic and ornithophilic Culicoides species. Host sequences found matches in horse (n = 59), sheep (n = 39), cattle (n = 26), Eurasian elk (n = 1) and 10 different bird species (n = 18). We identified 15 Culicoides species previously recorded in Scandinavia and four additional species haplotypes that were distinctly different from the described species. All ornithophilic individuals (n = 23) were caught exclusively in the suction traps, as were, interestingly, almost all mammalophilic species (n = 41), indicating that many biting midge species may be able to cover long distances after completing a bloodmeal. These results add new information on the composition of Culicoides species and their host preferences and their potential long-distance dispersal while blood-engorged.
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| 21. |
- Sigvald, Roland
(författare)
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Predicting the effects of climate change on the latency period of wheat leaf rust in western Poland
- 2017
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Ingår i: Acta Agriculturae Scandinavica, Section B - Soil and Plant Science. - : Informa UK Limited. - 0906-4710 .- 1651-1913. ; 67, s. 223-234
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Tidskriftsartikel (refereegranskat)abstract
- Leaf rust caused by Puccinia recondita f. sp. tritici belongs to the most important diseases of wheat worldwide. The progress of the disease is highly dependent on meteorological conditions. One of the parameters affecting the disease progress is latency period driven mostly by temperature. Examination of the influence of predicted temperature changes on the monthly sum of the daily latency period expressed as rate (MSLPR) in western Poland was the aim of our study. Experiments in quasi-natural conditions were performed with the aim of validating models describing the influence of temperature on leaf rust latency period in two wheat varieties, Turnia and Ostroga. Both models used for assessment of latency period duration on cv. Turnia and cv. Ostroga performed well. The influence of climate changes on leaf rust latency period was then simulated using meteorological data from three weather stations located in western Poland and virtual data obtained after transformation of the recorded data to reflect a temperature changes under RCP2.6 and RCP8.5 scenarios according to giss_e2_r climate model. The study shows that without mitigation of greenhouse gas emission latency period of wheat leaf rust is going to decrease which may result in increase of wheat leaf rust incidence.
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| 22. |
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