Biologisk bekämpning av potatiscystnematoder : några biologiska bekämpningsorganismer och deras potential för svenskt bruk

Potatiscystnematoderna (PCN) Globodera pallida (vit potatiscystnematod) och G. rostochiensis (gul potatiscystnematod) är sedentära endoparasiter på potatis som kan orsaka stora skördeförluster i potatisodlingar. Båda arterna av PCN är även klassade som karantänskadegörare i Sverige. I dagsläget finns det inga godkända nematicider i Sverige och effekten av PCN-resistenta potatissorter har på vissa håll minskat, vilket medför att biologisk bekämpning kan utgöra en viktig framtida bekämpningsåtgärd mot PCN. I det här arbetet utfördes en litteraturstudie för att undersöka några kontrollorganismer för tillsättande biologisk bekämpning mot PCN och huruvida organismerna är godkända som verksamma ämnen i Sverige. Arbetet avgränsades till att undersöka bakterier och svampar som antingen har verkningssätt mot PCN genom parasitism eller genom att de utsöndrar sekundära metaboliter (antibios) som påverkar PCN negativt. Resultatet visade att bakterierna Pseudomonas spp., Bacillus spp. och Pasteuria spp. har en kontrolleffekt mot PCN. Verkningssättet från Pseudomonas spp och Bacillus spp sker bland annat genom antibios och från Pasteuria spp genom obligat parasitism. Bland svamparna uppvisade Hirsutella rhossiliensis, Pochonia chlamydosporia, Verticillium leptobactrum, Purpureocillium lilacinum och Trichoderma spp. en bekämpningseffekt mot PCN. Bland dessa var H. rhossiliensis endoparasitär på PCN, medan de övriga svamparna var ägg- och/eller cystparasiter. Samtliga organismer har uppvisat en bekämpningseffekt mot båda arterna av potatiscystnematoder, frånsett Pasteuria spp., H. rhossiliensis och V. leptobactrum som endast uppvisat en kontrolleffekt mot G. pallida. Av dessa biologiska kontrollorganismer fanns det enligt Kemikalieinspektionens (KEMI) bekämpnings-medelsregister arter godkända som verksamma ämnen inom släktena Pseudomonas, Bacillus och Trichoderma. Trichoderma harzianum och Bacillus thuringiensis var de två arter som både omfattades av litteraturstudien och som var godkända som verksamma ämnen enligt KEMI:s bekämpningsmedelsregister. Det är i nuläget svårt att utvärdera vilka kontrollorganismer som har störst bekämpningseffekt eftersom de försök som gjorts har utförts på olika premisser och då inga av försöken utförts i svenska fältförhållanden. Däremot har vissa av organismerna uppvisat egenskaper i litteraturen som kan påverka deras lämplighet som biologiska kontrollorgansimer i svensk potatisodling. Vissa av kontrollorganismerna uppvisade även positiva bieffekter på potatisplantorna som exempelvis att de inducerade systemisk resistens och var tillväxtfrämjande, vilket är positiva egenskaper ur produktionssynpunkt. Slutsatsen som drog är att T. harzianum och B. thuringiensis är två kontrollorganismer som både finns godkända som verksamma ämnen i Sverige och som uppvisat en bekämpningseffekt mot PCN. Dock krävs mer forskning för att säkerställa att isolaten av dessa organismer lämpar sig för svenskt bruk samt i vilka formuleringar de ska appliceras.The potato cyst nematodes (PCN) Globodera pallida (white potato cyst nematode) and G. rostochiensis (yellow potato cyst nematode) are sedentary endoparasites of potato that can cause major yield losses in potato cultivations. Both species of PCN are also classified as quarantine pests in Sweden. At present, there are no approved nematicides in Sweden and the effect of PCN-resistant potato varieties has decreased in some areas, which means that biological control may be an important future control measure against PCN. A literature study was conducted to investigate some control organisms for augmentative biological control against PCN and whether the organisms are approved as active substances in Sweden. The work was limited to investigate bacteria and fungi that either have a mode of action against PCN through parasitism or by producing secondary metabolites (antibiosis) that affects the PCN negatively. The result showed that bacteria within Pseudomonas spp., Bacillus spp. and Pasteuria spp. have a control effect against PCN. The mode of action of Pseudomonas spp. and Bacillus spp. is through antibiosis and of Pasteuria spp. through obligate parasitism. Among the fungi, Hirsutella rhossiliensis, Pochonia chlamydosporia, Verticillium leptobactrum, Purpureocillium lilacinum and Trichoderma spp. showed a control effect against PCN. Among these, H. rhossiliensis was endoparasitic on PCN, while the other fungi were egg and/or cyst parasites. All organisms showed a control effect against both species of potato cyst nematodes, except for Pasteuria spp., H. rhossiliensis and V. leptobactrum, which only showed a control effect against G. pallida. Out of the studied biological control organisms there were species approved as active substances according to the Swedish Pesticides Register of the Swedish Chemicals Agency (KEMI) in the genera Pseudomonas, Bacillus and Trichoderma. Trichoderma harzianum and Bacillus thuringiensis were the two species that were both included in the literature study and approved as active substances according to the Swedish Pesticides Register. Currently, it is difficult to evaluate which control organisms have the greatest control effect since the experiments have been carried out on different premises and since none of the experiments have been carried out in Swedish field conditions. However, some of the organisms have shown characteristics in the literature that may affect their suitability as biological control organisms in Swedish potato cultivation. Some of the control organisms also showed positive side effects on potato plants, such as inducing systemic resistance and promoting growth, which are positive characteristics from a production point of view. The conclusion that was drawn is that T. harzianum and B. thuringiensis are two control organisms that are both approved as active substances in Sweden and have shown a control effect against PCN. However, more research is needed to ensure that the isolates of these organisms are suitable for Swedish use and in which formulations they should be applied

Effect of different inoculation methods in modern and historic cultivars of soybean suitable for cultivation in Sweden

The inclusion of soybean in Swedish crop rotations would enable an increase in legume production in Sweden. Previous attempts to introduce soybean as a crop in Sweden have failed, but in recent years, new attempts have been made under experimental conditions. Soybean cultivars suitable for cultivation in Sweden belong to maturity group (MG) 000, as well as historically Swedish-bred soybean cultivars, such as Bråvalla. However, for these cultivars to fix N, compatible rhizobia such as Bradyrhizobium japonicum are needed. These are not native to Swedish soils and have to be introduced through inoculation. Inoculating seeds can have several beneficial effects on soybean traits, but this varies with the interaction between soybean cultivar, rhizobial strain- or species and environmental factors. Inoculants can have different formulations which have different properties and may affect rhizobial survival and inoculation effect. The aim of this thesis was to evaluate the effects the inoculation methods no-, liquid- or peat inoculation had on phenotypic traits and N-fixation in soybean cultivars suitable for cultivation in Swedish climate in both field- and greenhouse conditions. The peat- and liquid inoculants containing B. japonicum, as well as uninoculated control, were tested in a field trial on Gotland, Sweden, on the soybean cultivars Abaca, Gallec, Sussex, and Todeka (all MG 000), and in a greenhouse experiment in Uppsala, Sweden, on the cultivars Abaca, Gallec, Sussex and Bråvalla (historic). Inoculation of the seeds resulted in higher N content and %Ndfa in both the field trial (significant increase) and the greenhouse experiment compared to the uninoculated plants. The peat – and liquid formulations did not differ in performance in the greenhouse experiment, but the peat inoculant did overall perform better than the liquid inoculant in the field trial. This may be an effect of the protective properties of peat supporting rhizobial survival in field conditions. Inoculation of the seeds did not have a significant effect on the traits: plant height, height of the lowest node, leaf biomass, or N content in the leaves at flowering (field trial). However, inoculation significantly affected: TKW, yield, root biomass, stem biomass, root-/ stem biomass ratio, nodule weight, nodule number, and protein yield compared to uninoculated plants. The responses to the inoculants varied between the environments and between cultivars. In comparisons between the greenhouse experiment and the field trial, the traits affected by rhizobial survival (N content, nodule number and nodule weight) were enhanced in the greenhouse experiment, while traits probably limited by light intensity (TKW and yield) were superior in the field trial. The results showed that the interaction between cultivar x inoculation method had a significant effect on: root biomass, stem biomass, root-/stem biomass ratio, nodule number, nodule weight (GH), TKW, yield (GH), N content in biomass and seeds and %Ndfa in biomass and seeds. This thesis demonstrated that peat inoculation was superior over liquid inoculation in Swedish field conditions and that the MG 000 cultivar Sussex in comibination with LegumeFix had the greatest potential for generating high yield and protein yield out of the tested combinations, hence being suggested to Swedish farmers wanting to try soybean cultivation. However, further research is needed to confirm these results