Foliar diseases incited by ascomycota/deuteromycota

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Int 256/FSC 300 - Laboratory #3: Page

Laboratory #3


(Edmonds p. 228-231, 237-253, 309-320)


To observe and study foliage diseases of trees.


Dissecting microscope or hand lens, compound microscope, razor blade, forceps, water, slide, cover slip.

.IIIPart 1: Introduction to the Study of Fungi (Mycology)

(Volk, T. 2000. The Kingdom Fungi. )

.ACharacteristics of Fungi.

.1Primary attributes.

)aHeterotrophic (achlorophyllous).
)cCell walls.
)dMycelial growth form.
)eReproduction by spores.

()aGrowth cessation (dormancy).

()bGrowth resumption (germination).


()iiiAsexual (imperfect).
()ivSexual (perfect).

()aPlasmogamy (N+N) and karyogamy (2N).


()cHaploid (1N), dikarion (N+N), and diploid (2N).


()iHypha (hyphae)

()aWith nucleus

()bWith or without septa.
()iiMycelium (mycelia). collection of hyphae

.BClassification - Based on How Spores Are Produced.

.1Zygomycota (Phycomycetes) (lower fungi).

)aNonseptate hyphae.
()iiSporangiospores (motile).

.2Deuteromycota (Fungi Imperfecti or Deuteromycetes).

)aAbsence of a sexual state.
)bConidia and fruiting structure.

.3Ascomycota (Ascomycetes).

()iAscus and ascospores.




.4Basidiomycota (Basidiomycetes).

()iBasidia and basidiospores.


()b"Shelf" fungi.

)cRust fungi.
()i5 spore stages
()ii2 hosts

.IVPart 2: Hardwoods

.APowdery mildews (class web site)

.1Identify the genus.

)aUsing the dissecting microscope, examine leaves of red oak (Quercus rubra) infected by the powdery mildew fungus. Notice the signs of disease, the white mycelium on the leaf surface and the presence of black cleistothecia.
)bIdentify the fungus to genus using the diagrams on the pathogen cycle and the key (see below).
()iPick off cleistothecia with a needle and razor blade and place them in a drop of water on a slide.

()aVerify the presence of cleistothecia in the drop of water by using the dissecting microscope or hand lens.

()bPlace a cover slip over the water drop, but do not press.

()iiObserve the appendages on the cleistothecia.
()iiiSplit open the cleistothecia and count the number of asci.
()iOne ascus per cleistothecia.

()aAppendages mycelioid: Sphaerotheca.

()bAppendages dichotomously branched: Podosphaera.

()iiSeveral asci per cleistothecium.

()aAppendages mycelioid: Erysiphe.

()bAppendages dichotomously branched: Microsphaera.

()cAppendages with a bulbous base: Phyllactinia.

()dAppendages with coiled tips: Uncinula.

.2Complete a disease description

)aDisease tree/symptoms; inciting stress/signs, environment.
)bBe sure to diagram and label the following:
()iOverall appearance of fungus on leaf.
()iiCleistothecia with appendages.
()iiiAsci and ascospores.

.3Repeat all steps for red maple (Acer rubrum) leaves.

.BOak leaf blister. (class web site)

.1Examine oak leaf blister incited by the fungus Taphrina. Your sketch should indicate:

)aAreas of discoloration.
)bAny abnormal growth of the leaf tissue ("blisters") known as hypertrophy.

.2Examine a prepared slide of Taphrina and identify the ascus and ascospores.

.CAnthracnose. (
( (class web site)

On maple (Acer) incited by Kabetiella sp.

.1Examine leaves of maple for symptoms of the disease anthracnose.

.2Note location of necrotic tissue in relation to the leaf margin and veins. This will help distinguish this disease from other problems (e.g. drought, nutrient deficiencies) commonly found on trees.

.3There are no apparent signs on these samples.

.DTar spot of maple (Acer) (class web site)

.1Observe the signs and symptoms of tar spot caused by Rhytisma. Identify the stroma formed by the pathogen.

.2Find an apothecium of Rhytisma on a prepared slide. Label stroma, apothecium, asci, leaf tissue.

.EElm leaf spot (class web site)

.1Examine elm (Ulmus) leaves affected by leaf spot and note the differences in symptoms with those of anthracnose.

.2Examine prepared slides of elm leaf spot and locate perithecia of the pathogen (Gnomonia is the Latin name for the sexual stage, Gloeosporium is the Latin name for the asexual stage (not seen)).

.VDiseases Part 3: Conifers

.ANeedle cast (Necrophytes).

.1Obtain pine (Pinus spp.) needles infected with Lophodermium.

)aUsing a dissecting microscope, learn to recognize the distinctive fruiting structure of this fungus (elongated apothecia or hysterothecia).

.2Obtain balsam fir (Abies balsamea) needles infected with Isthmiella (= Bifusella) and learn to recognize the pycnidia (asexual) and hysterothecia (sexual) of this species. ( (class web site)

.3Examine Douglas-fir (Pseudotsuga menziesii) needles infected by Rhabdocline.
( (class web site)

)aCompare apothecia of this fungus with the hysterothecia of the previous two Ascomycetes and note the differences in shape, size, and location on the needle.
)bNote the pattern and color of necrotic tissue associated with this fungus.
)cExamine a prepared slide of infected needles with a compound microscope. Identify asci and ascospores.

.4Examine Douglas-fir needles affected by Swiss needle cast, incited by Phaeocryptopus (= Adelopus). (

)aIdentify the minute perithecia emerging from stomata.
)bNote how the necrotic tissue forms no distinctive pattern on the needles.
)cExamine a prepared slide. Label needle tissue, stomata, and perithecia.


Disease Complexes.

Powdery mildews


elm leaf spot

Isthmiella needle cast

Lophodermium needle cast

oak leaf blister

Rhabdocline needle cast

Swiss needle cast

tar spot

Latin Names






Isthmiella (=Bifusella)




Phaeocryptopus (= Adelopus)

















leaf spot

needle cast




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