Endophytes: biocontrol killers?

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Endophytes: biocontrol killers?. Sarah Dodd, Daniel Than, Stanley Bellgard and Chris Winks (LCR) Rebecca Ganley (Scion) Trevor James (AgR). Endophytes. All plants are infested with microbes Symptomless Epiphytes/ Endophytes Balanced status of symbiosis = Majority Disease Pathogens - PowerPoint PPT Presentation

Text of Endophytes: biocontrol killers?

  • Endophytes: biocontrol killers?Sarah Dodd, Daniel Than, Stanley Bellgard and Chris Winks (LCR)Rebecca Ganley (Scion)Trevor James (AgR)

  • Endophytes

    All plants are infested with microbes

    SymptomlessEpiphytes/EndophytesBalanced status of symbiosis= MajorityDiseasePathogensUnbalanced status of symbiosis

  • Endophyte/Plant relationshipEndophyte gains shelter and nutrientsPlant cost nutrients and resources(e.g. more susceptible to pests and diseases: BCAs)Plant gains Growth promotion (enhanced nutrient uptake)Increased tolerance to harsh environments (e.g. drought tolerance)Induced Resistance to pests and diseases (BCAs)

  • Endophytes weeds and weed biocontrolHarry Evans (2007) proposed:

    Weediness: Endophytes influence the fitness of a plant and therefore its invasivenessBiocontrol: Endophytes interact with plants and/or biocontrol agents either enhancing or reducing their activity

  • Microbial interactionsPathogensEndophytes/epiphytes

    AntibiosisParasitismCompetitionCell lysis

  • Microbe interactions under the microscope

  • Weed / Endophyte systems under investigation in NZSclerotinia on Californian thistle Phoma on Old Mans BeardWilding GingerPrivetPampas

  • Sclerotinia on Californian thistle- a mycoherbicide

    1. Kills entire plant2. Partially kills plantPlant recovers3. No effect on plant

  • AimTo identify microbes that influence the success/failure of a pathogen biocontrol agent

    To ultimately manipulate interactions to improve consistency of weed biocontrol activity

  • Progress: step 1determine population variationRoots, shoots, flowers & seeds

  • Methods - to identify endophytesCulturing isolate & identify key endophyte fungi

    DGGE - DNA profile comparisons- endophyte fungi and bacteria - DNA sequence to identify bands (microbes)

  • Culturing isolation and identification

  • Molecular -DGGESamples are all assessed and bands(microbes) identifiedVariability between tissues/plants/fields has been assessed

  • Endophytic microbes from thistle (closest GenBank match)CulturingDGGEKnown biologyFungi - AscomycotaAlternaria sp.Aureobasidium pullulansBionectria sp.Botryosphaeria laricinaCladosporium cladosporioidesCladosporium sp.Codinaeopsis sp.Colletotrichum acutatumCryptococcus rajasthanensisCurvularia sp.Cylindrocarpon sp.Davidiella tassianaEpicoccum nigrumEudarluca caricisExophiala sp.Fusarium cortaderiae Fusarium oxysporum Fusarium solani Fusarium sp. 1.Hypocrea/TrichodermaLeptodondium orchidicolaLewia infectoriaNeonectria radicola Nigrospora oryzaePhaeococcomyces chersonesosPhoma exiguaPhoma sp.Phomopsis theicolaPhomopsis sp.Pichia fermentansPlectosphaerella cucumerinaPlectosphaerella sp.Preussia isomeraPreussia sp.Pyrenochaeta terrestrisSclerotinia sp.Stachybotrys echinataStemphylium sp.Verticillium dahliaeXylariaceae sp.L,SSL--L,S-L,S,PSL--L--LRRL,RLL,RLRL--RLL---LL-L--S,RL,S,PLRPS-LSR-RL--RSL,S,R,PL,SR-R----L--RL,R---LRL-L,R,PR-LSL,P-saprobepossible plant pathogen or saprobepossible plant pathogenpossible secondary pathogensaprobesaprobesaprobepossible secondary pathogenyeast-like saprobegrass pathogenpossible plant pathogensaprobesaproberust mycoparasitesaprobepossible plant pathogenpossible plant pathogenpossible plant pathogenpossible plant pathogenPossible mycopathogensaprobesaprobepossible plant pathogensaprobesaprobeplant pathogenpossible secondary pathogen or saprobePossible secondary pathogen or saprobepossible secondary pathogen or saprobeyeastplant pathogenpossible plant pathogencoprophilous saprobecoprophilous saprobeonion path/soil saprobeplant pathogensaprobesaprobeplant pathogensaprobe

  • Endophytic microbes from thistle (closest GenBank match)CulturingDGGEKnown biologyFungi - BasidiomycotaBovista plumbea Ceratobasidium sp.Cyathus stercoreusExidiopsis sp.Flammulina velutipesGloeoporus dichrousKuehneromyces rostratusLangermannia giganteanLimonomyces roseipellisMelampsora laricis-populinaMycena sp. / Nolanea sp.Panaeolus sphinctrinusPeniophora pini / aurantiacaPleurotopsis longinquaPleurotus pulmonariusPuccinia chrysanthemi / carduorum Puccinia cnici-oleraceiRogersella griseliniae / Hyphodontia crustosa Schizophyllum communeTomentellopsis submollis / bresadoliana



    saprobepossible plant pathogensaprobesaprobesaprobesaprobesaprobesaprobesaprobeplant pathogen (rust)saprobesaprobesaprobesaprobepossible plant pathogenplant pathogen (rust)plant pathogen (rust)saprobesaprobesaprobeBacteriaPantoea sp.L,R-unknown

  • Testing influence of endophytesGlasshouse trials assess disease developmenta) BCA + key endophyteb) BCA - key endophyte

  • Preliminary glasshouse trialsCan endophytes influence Sclerotinia disease? No influenceEnhanced Sclerotinia diseaseReduced Sclerotinia disease (e.g. Colletotrichum sp.)

  • SummaryWe now have evidence to support the theory that endophytes DO influence the activity of pathogen biocontrol agents

  • The FutureSclerotinia on Cali thistleIdentify key bacterial endophytesContinue glasshouse testingIdentify key endophyte modes of actionImprove pathogen biocontrol agent activityOther plant systemsIdentify key endophytes and test in glasshouseEndophytes and insect BCAs

  • Californian thistle PhomaCalifornian thistle rust

    **AntibiosisParasitismCompetition for nutrients/nicheCell lysis

    *Speculated activity of endophytes:

    Harry Evans Hyopthesis:

    Enhanced plant growthProtect plant against pathogensDrought resistance

    In absence, more vulnerable to these.Drain on plant resources making more vulnerable to pathogensMutualist hypothesis: Recent work has indicated that mutualists may be critical for successful plant invasion. Richardson et al. (2000) extensively reviewed the literature on the importance of pollinators, nitrogen-fixing bacteria, soil mycorrhizae and vertebrate seed-dispersers in plant invasions and also noted that there has been growing interest in the role of leaf fungal endophytes in conferring an advantage to plants in the presence of herbivores (e.g. Clay 1996). As with arbuscular mycorrhizal fungi, these associations appear to be widespread in the plant kingdom. Yet the specificity and nature of the associations (mutualistic or pathogenic) are poorly known, as is their role in invasion. We hypothesise that non-invasive exotic species may lack key mutualist species. Indeed, the probability of an exotic species being imported without its natural enemies, while retaining or acquiring new key mutualist species is likely to be very low. Furthermore, while mutualist species may afford plants some protection from natural enemies, if their presence comes at a metabolic cost, they may actually be a disadvantage in the introduced range where natural enemies may be absent. Earlier this year, a new hypothesis was presented by Dr Harry Evans, the endophyte-enemy release hypothesis (E-ERH), which we believe warrants further investigation. Dr Evans proposes, with the support of circumstantial evidence, that it is the presence or absence of mutualistic endophytes that plays a key role in determining why some alien plants become invasive.Endophytes are micro-organisms that colonize the tissues of healthy plants. There is compelling evidence of plant/endophyte mutualism, with mutualistic endophytes offering a variety of potential benefits to their host plants: 1) growth enhancement (Varma et al. 1999); 2) tolerance to abiotic factors (such as drought, heat and heavy metals; Rodriguez & Redman 2005; Rodriguez et al. 2004; Marquez et al. 2007)); and 3) resistance to pests and disease (Latch 1993; Christensen 1996; Clay 1997; Schardl & Phillips 1997; Stone et al. 2000). See also Redman et al. (2001); Rudgers et al. (2004); and Schulz & Boyle (2005). In return, endophytes are thought to benefit from the comparatively nutrient rich, buffered environment found inside plant tissues. A. The endophyte-enemy release hypothesisHow mutualistic endophytes could enhance plant invasiveness: Plants arriving in a new location without co-evolved natural enemies, but with mutalistic coevolved endophytes, or forming mutualistic associations with indigenous endophytes, would have a greater resistance to natural enemies and abiotic factors, giving them an advantage over local competitors. How a lack of mutualistic endophytes could enhance plant invasiveness: There is a cost to the plant in harbouring endophytes, and consequently those alien plants arriving and remaining endophyte-free, without coevolved natural enemies, would have a distinct competitive advantage since they would have more resources to allocate to growth and reproduction.The endophyte-enemy release hypothesis therefore explains why classical biological control can be unpredictable as a management strategy. In the absence of endophytes, exotic plants with weedy traits would be vulnerable to co-evolved natural enemies. Hence, subsequent introductions of a single biological control agent can successfully, and often unexpectedly, bring about the complete control of a rampant invasive weed. In contrast, weedy exotic plants complete with their cohort of co-evolved endophytes would be protected from introduced natural enemies, making such enemies unsuitable for biological control.

    1. Californian thistle Sclerotinia BCA vs endophyte population2. Phoma on Old Mans Beard3. Endophytes of wilding ginger Invasivenessintroduced vs place of origin (India)4. Privet endophytes5. Pampas endophytes

    ****When looking for microbe populations associated with a particular activity, it is important to know the level of natural variation in such populations as this will impact on the number of samples required to expose them. As there is currently no data availabl