Title: Electron microscopic examination of plant disease samples from Mexico
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Title: Electron microscopic examination of plant disease samples from Mexico
Physical Description: Book
Creator: McCoy, Randolph E.
Publisher: Agricultural Research and Education Center, IFAS, University of Florida
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Bibliographic ID: UF00076397
Volume ID: VID00001
Source Institution: University of Florida
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Resource Identifier: oclc - 133164109

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b VFort Lauderdale, Florida --.










Electron Microscopic Examination of Plant

Disease Samples From Mexico








Randolph E. McCoy








University of Florida Agricultural Researc Report
FL 84 2 "

February 1984 f,


University of Florida I.F.A.S.
Agricultural Research and Education Center
3205 S.W. College Avenue
Fort Lauderdale, Florida 33314





- 1 -


Samples from three plant diseases from Mexico were examined by transmission

electron microscopy. Samples were collected from two plants for each disease;

three samples from each plant being prepared for embedment in Spurr's plastic.

At least five ultrathin sections of plant tissue were examined from each of

the three samples taken per plant.


Samples were cut into 0.5 cm pieces and placed in 2% paraformaldehyde 2%

gluteraldehyde fixative overnight, then placed in 0.1 m cacodylate buffer.

Samples were shipped in histocon buffer to preserve structural detail during

shipment. Upon arrival in Fort Lauderdale, samples were cut into 0.5mm

pieces in fixative, post fixed in 2% OsO4, and embedded. An en block

stain of lead aspartate was used.


Sample 1: Grapevine 'Ruby Cabernet'

Symptoms included stunted leaves and fruits, plants of low stature, leaves

with reddish areas, low yield.


Tissues sampled included petioles, stem, and bud from young tissues and a

petiole base from mature leaf with reddish discoloration.


Observations: No mycoplasmalike organisms were observed in phloem cells

(plates 1 & 2). No xylem-limited bacteria were observed (plate 3). Some

crystaline aggregates were observed in parenchyma cells, however, these are

considered normal in grapevine (plate 4).


Conclusions: No evidence of infection by mycoplasmalike organisms or by the

Pierces' disease xylem-limited bacterium was obtained.






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Sample 2. Walnut, Texas root rot disease.

Examination of the walnut samples revealed the presence of normal-appearing

xylem (plate 5) and phloem (plate 6) tissues. No evidence of mycoplamal

or bacterial infection was obtained. Unless misdiagnosed, Texas root rot

disease is a classic infection of the root system by the fungus Phymatotrichum

omnivorum. The disease is very important in the south central USA and northern

Mexico. It is highly destructive and affects a large number of crops. The

disease is favored by hot weather and is inhibited during the coolor part

of the year.


Sample 3: Cotton, white fly damage

Examination of cotton samples revealed crystaline aggregates of virus in

epidermal cells (plates 7 and 8). Xylem and phloem appeared normal.


Conclusion: No evidence of infection by mycoplasmalike organisms or xylem

bacteria was observed. It is most likely that this disease is of viral

origin. The leaf crumple disease of cotton has been reported in the

southwestern USA and Mexico. This virus is transmitted by white fly.




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Plate 1: Normal sieve tube cells of phloem of grapevine,
(Negative 5562).


10,000 X.


Plate 2: Normal sieve tube cells of phloem of grapevine, arrow shows
normal P-protein, 7,000 X. (Negative 5560).


I




-4-


Plate 3: Normal vessel elements of xylem of grapevine, 3,000 X.
(Negative 5561).


Plate 4: Crystaline aggregates in parenchyma cells of grapevine,
20,000 X. (Negatives 5552/5547).




-5-


Plate 5: Normal vessel elements of xylem of walnut, 3,000 X.
(Negative 5558).







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Plate 6: Normal phloem tissues of walnut, 7,000 X. (Negative 5557).




-6-


Plate 7: Virus crystals in epidermal cells of cotton, 15,000 X.
(Negative 5603).




























Plate 8: Virus crystals in epidermal cells of cotton, 10,000 X.
(Negative 5602).




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