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Plant endophytes


Here fungi enter the scene
Fungal endophytes: 1) Inhabit every plant; 2) Produce many chemicals solely or in the interaction with host plant; 3) Have full spectrum from parasitism to commensalism (but most of them are not parasites -- Ganley, Brunsfeld & Newcombe, 2004).

Are endophytes involved in the creation of "weed of mass destruction"?


Isolation
Endophytes are usually isolated from the achenes of knapweed

endophytefree achenes


Endophyte-free plants
Plants from natural habitats are usually rich of endophytes (70%­90% of seeds). If vertical transmission accounted for the presence of endophytes in seeds of surveyed plants, then infected plants would produce seeds from which we would isolate endophytes at field incidence. This is not the case: seeds have been free of endophytes.


Competition experiment
E+ knapwe ed and fescue

Fescue alone: control

Endophyte-free (E­) knapweed and fescue


The differences in fescue biomass are statistically significant
Least Squares Means
6 1 0 04 0 0 R A V2

1 E­ plants 2 E+ plants C Control (Festuca idahoensis alone)

0

1

2 C VAR00002


How diverse are knapweed endophytes?

MP tree from phylogenetic analysis of ITS1, 5.8S and ITS2 gene sequences


M os t frequent ITS haplotypes

Botrytis spp., 6 ITS haplotypes

Alternaria spp., 5

Fusarium spp., 5 (all are new to GenBank)


Distribution among native and exotic ranges

Present in both ranges


Are endophyte communities different?
exotic range

native range


Patterns of co-occurrence
Haplotypes common to exotic range Haplotypes common to native range

To both


Host-jumping vs. co-introduction
· Endemic or nearly endemic ITS haplotypes; Explanation of effect from Callaway et al.; Communities form two "clouds" on ordination · 6 (25%) identical ITS haplotypes from both ranges; Eurasian origin of some sequences; Some communities are "intermediate" on ordination

· ·

· ·


Endophytes and seed germination


Some endophytes are capable to terminate seed growth
no termination intermediate "behavior"

heavy termination


Liquid cultures and volatile compounds


Gas chromatogram: highest pike corresponds with sesquiterpene

At least some endophytes can produce sesquiterpenes


Conclusions
· There are huge diversity of fungal endophytes in the knapweed (> 24 species), endophyte communities are also different

·

The endophytes of knapweed are capable (a) to inhibit the growth of fescue grass, (b) to terminate the germination of seeds, (c) to produce volatile compounds (sesquiterpenes)