Home About Browse Search
Svenska


Dahlberg, Caroline, 2009. Svampar associerade med raps : betydelse för uppkomst och grödetablering. SLU, Dept. of Forest Mycology and Plant Pathology, Uppsala. Uppsala: SLU, Dept. of Forest Mycology and Plant Pathology

[img]
Preview
PDF
459kB

Abstract

Oilseed rape is an important crop in Sweden and is grown on about 90000 ha today. The interest in oil seed pro-duction is increasing because of growing demand and high prices for oil seed both in Sweden and Europe. However, an increased intensity in the oil seed production can bring higher risk of yield losses due to fungal diseases. The purpose of this study was to investigate what different fungi are associated with oilseed rape under field conditions and if their incidence is correlated to crop establishment problems.
This study was carried out in three parts: 1) investigations on fungal community structure in roots and rhizosphere soils from young spring- and winter rape plants sampled in failed respectively good establishment patches in four fields, 2) investigations on the pathogenicity of fungi isolated from oilseed rape in controlled environment and 3) investigations on the effect of different fungicide seed treatments on germination and early plant development in a field soil naturally infested with damping off- and Verticillium wilt pathogens.

The studies on community structure using a combined approach of standard fungal isolation techniques and DNA based methods revealed a high fungal diversity in three out of four studied fields of spring rape and winter rape. For some unknown reason, very few fungal species were identified from the fourth field. Fungi belonging to establishment related pathogenic groups e.g. Rhizoctonia, Fusarium, Phoma and Alternaria were found in both spring- and winter rape. Also Verticillium, a pathogen attributed to wilting in late crop stages was found in both crops. In general, the plants from patches with good establish¬ment seemed to carry a higher number of fungal species than plants from patches with a poor establishment. Possibly, the potentially pathogenic fungi exist in equilibrium with non-pathogenic fungi in the good establish¬ment patches and whereas in poor patches fungal pathogens are favoured by being able to attack plants already weakened by other factors. This hypothesis, however, needs further investigations.

The greenhouse study on effect of potentially pathogenic fungi on emergence and early growth showed that all tested fungi affected the emergence/plant growth compared to the uninoculated control. Rhizoctonia solani proved to be the most severe pathogen. Damping off-like symptoms and/or hampered plant growth due to Fusarium and/or Alternaria were also observed but the damage caused by these fungi was not statistically different from the control in this short term study.

The greenhouse seed dressing study demonstrated that most of the tested compounds did not protect the seed-lings from damping off. In general, most treatments affected the rape seedlings negatively in some way. The only fungicide showing good effect was metalaxyl which is known to be effective only against oomycetes. This indicates that the field soil used in the experiment probably also carried oomycetous pathogens. Lack of detection of oomycetes in the community study is most likely due to the choice to use only fungal specific primers.

The results indicate that there is a risk of losses due to bad crop establishment of oils seed caused by pathogenic fungi. This risk might be accentuated by low seed rates in especially winter rape. The combination of low plant density in the oil seed fields and an increased population of pathogenic fungi can increase economic risks. In a situation with increasing intensity in the oil seed production it is important to have knowledge about the role of fungal pathogens on early oil seed crop establishment.

,

Idag odlas ca 90 000 ha oljeväxter i Sverige. Intresset för odling av oljeväxter växer i takt med en ökande efterfrågan
i både Sverige övriga EU. En ökad oljeväxtodling är emellertid inte helt oproblematisk, eftersom en intensivare
odling gynnar flera sjukdomar som kan orsaka allvarliga skördeförluster. Syftet med detta examensarbete
var att undersöka vilka svampar som förekommer i rapsfälten och få en bild över vilken betydelse dessa
kan ha på etablering av rapsgrödan.
Examensarbetet har utförts i tre olika delar; 1) en inventering av svampar i vår- och höstrapsfält,
2) ett patogenitetstest i steriliserad jord i växthus samt 3) ett betningsförsök för att undersöka effekten av olika
pesticidbehandlingar mot etableringsskadegörare i oljeväxter.
Kartläggningen av svampar i fält som gjorts i detta examensarbete visade på en hög artdiversitet. Patogena
svampar som återfanns i både vår- och höstraps var bland annat Rhizoctonia, Fusarium, Phoma, Alternaria samt
Verticillium. Ett större antal svamparter konstaterades i rutor med bättre etablering än i rutor med sämre etablering.

Patogenicitetstestet utfördes med svampar som isolerats vid fältinventeringen. Rhizoctonia solani påverkade
grödan starkast, och alla behandlingar med R.solani påverkade plantorna på något sätt jämfört med kontrollen,
Inokulering med Phoma, Fusarium samt Alternaria påverkade inte plantorna i lika stor omfattning som R.
solani. Symtom orsakade av dessa svampar är svåra att se i fält och därför kan betydelsen av angrepp underskattas.
En intensivare odling kan dessutom bidra till en ökad risk för skador orsakade av dessa patogener.
Betningen sänkte grobarheten i flera led och försämrade fröets motståndskraft och gav inga större effekter mot
groddbränna. Undantaget var ledet betat med preparat innehållande metalaxyl där inga symtom kunde observeras
på plantorna. En behandling (Rovral + Chinook) resulterade i signifikant fler sjuka plantor än vad som kunde
observeras i den obetade kontrollen. Vid isolering av svampar från de infekterade plantorna i betningsförsöket
kunde Rhizoctonia observeras i obehandlat led och i ledet med Magnate 50+Modesto. Förklaringen till att mera
sjuka plantor kunde observeras i detta kan bero på att betningen påverkade svampsamhällets sammansättning.
Detta kan ha givit utrymme åt Rhizoctonia att ge större angrepp. Den bästa effekten gav betning med Crusier.
Detta preparat innehåller metalaxyl, en systemisk fungicid som kan absorberas i plantan genom blad, stjälk eller
rot. Metalaxyl har emellertid bara effekt på oomyceter. Förekomsten av oomyceter undersöktes inte i detta examensarbete.
En strävan mot lägre utsädesmängder kan medföra stora risker då marginalerna blir mindre. Dessa gronings- och
etableringspåverkande patogener anses idag inte vara av någon större ekonomisk betydelse, men det är viktigt att
ha kunskap om dessa patogener när rapsarealerna ökar.

Main title:Svampar associerade med raps
Subtitle:betydelse för uppkomst och grödetablering
Authors:Dahlberg, Caroline
Supervisor:Alström, Sadhna
Examiner:UNSPECIFIED
Series:UNSPECIFIED
Volume/Sequential designation:UNSPECIFIED
Year of Publication:2009
Level and depth descriptor:Other
Student's programme affiliation:1010A Agriculture Programme (admitted before July 1, 2007) 270 HEC
Department:(NL, NJ) > Dept. of Forest Mycology and Plant Pathology
(S) > Dept. of Forest Mycology and Plant Pathology
Keywords:oljeväxter, grödetablering, patogena svampar
URN:NBN:urn:nbn:se:slu:epsilon-s-8925
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-s-8925
Subjects:SLU > (NL, NJ) > Dept. of Forest Mycology and Plant Pathology
SLU > (S) > Dept. of Forest Mycology and Plant Pathology

Plant ecology
Language:Swedish
Deposited On:17 Nov 2017 10:51
Metadata Last Modified:17 Nov 2017 10:51

Repository Staff Only: item control page

Downloads

Downloads per year (since September 2012)

View more statistics

Downloads
Hits