Ultrastructure of wilt syndrome caused by Verticillium dahliae. III. Chronological symptom development in sunflower leaves

1977 ◽  
Vol 55 (2) ◽  
pp. 139-152 ◽  
Author(s):  
Jane Robb ◽  
Lloyd Busch ◽  
Jean D. Brisson ◽  
B. C. Lu
Keyword(s):  
Phenolic Compounds ◽  
Verticillium Dahliae ◽  
Temporal Order ◽  
Band 3 ◽  
Xylem Vessel ◽  
Ultrastructural Changes ◽  
Symptom Expression ◽  
Symptom Development ◽  
Mesophyll Tissue ◽  
Foliar Symptom

When sunflowers are infected by the vascular pathogen Verticillium dahliae, the first visible foliar symptom is the appearance of tiny chlorotic flecks. An attempt was made to determine the temporal order in which early ultrastructural changes leading to symptom expression occur. The evidence indicates that ultrastructural changes occur in the following order: (1) degradation of xylem vessel walls, (2) initiation of the necrotic band, (3) degeneration of the mesophyll tissue remote from the vein, and (4) degeneration of the phloem. The possible importance of xylem vessel plugs and of phenolic compounds to the initiation of symptom development is also discussed.

Ultrastructure of wilt syndrome caused by Verticillium dahliae. II. In sunflower leaves

1975 ◽  
Vol 53 (23) ◽  
pp. 2725-2739 ◽  
Author(s):  
Jane Robb ◽  
Lloyd Busch ◽  
Jean D. Brisson ◽  
B. C. Lu
Keyword(s):  
Verticillium Dahliae ◽  
Vascular Diseases ◽  
Degenerative Changes ◽  
Ultrastructural Changes ◽  
Foliar Symptoms ◽  
Leaf Mesophyll ◽  
Mesophyll Tissue ◽  
Vessel Elements ◽  
Verticillium Dahliae Kleb ◽  
Made In

Ultrastructural changes occurred in sunflower leaves that were infected by Verticillium dahliae Kleb. during the appearance of foliar symptoms. Early in symptom development major degenerative changes took place in the leaf mesophyll tissue particularly in the vicinity of the xylem of the major veins. During these early stages vessel wall breakdown occurred in the vicinity of the fungus, but this degradation was not accompanied by swelling. Occlusion of the vessel elements by fungus, fibrillar material, or electron-dense plugs was not significant until late in disease development. Comparison of these observations with those that were made in a previous parallel study of Verticillium-infected chrysanthemum suggested that the ultrastructural changes induced by the fungus in the two hosts are similar but that the timing is different. In chrysanthemum, degenerative changes in the mesophyll are not extensive until after chlorosis, but vessel blockage is advanced before wilting is noticeable. The significance of this difference in the development of foliar symptoms is discussed in relation to the plugging and toxin theories of wilt induction in fungus-caused vascular diseases.

scholarly journals Development, Detection, and Elimination of Verticillium dahliae in Mint Shoot Cultures

HortScience ◽  
2003 ◽  
Vol 38 (1) ◽  
pp. 67-70 ◽  
Author(s):  
Nan Wang ◽  
Barbara M. Reed
Keyword(s):  
Verticillium Dahliae ◽  
Shoot Tips ◽  
Potato Dextrose Agar ◽  
Shoot Length ◽  
Symptom Expression ◽  
Shoot Cultures ◽  
Symptom Development ◽  
Symptom Ratings ◽  
Wilt Symptom

Roots of greenhouse-grown mint plants and in-vitro-grown shoot cultures were inoculated with Verticillium dahliae Kleb. conidial suspensions to study wilt symptom development and detection and elimination of the fungus. There were significant differences in the symptom expression between control and infected shoot cultures at all conidia concentrations for the four mints tested. Disease-symptom ratings were proportional to the V. dahliae inoculum density. Infected shoot cultures were stunted when inoculated with ≥ 103 conidia/mL. Verticillium dahliae was re-isolated from infected shoot cultures at all levels of inoculum, but not from any control cultures. Verticillium infections were easily detected by plating mint stems on potato dextrose agar. Shoot tips (0.5 to 15 mm) from infected in-vitro- and greenhouse-grown plants were isolated and screened for fungus. The most effective shoot length for fungus elimination was 3-5 mm. Shoot tips isolated from in vitro spearmint cultivars infected at 102 and 103 conidia/mL were 100% Verticillium free, but only 42% of `Black Mitcham' and 54% of `Todd's Mitcham' peppermints were free of the disease. Shoot tips from infected greenhouse plants produced Verticillium-free cultures from 79% of `Black Mitcham' and 90% of `Todd's Mitcham' plants. These results indicate the utility of testing for Verticillium and the safety of micropropagated mint shoots for certified planting stock programs.

Monitoring foliar symptom expression in beech leaf disease through time

2022 ◽  
Author(s):  
Carrie J. Fearer ◽  
Daniel Volk ◽  
Constance E. Hausman ◽  
Pierluigi Bonello
Keyword(s):  
Symptom Expression ◽  
Leaf Disease ◽  
Foliar Symptom

Cyanogenic potential of Trifolium repens L. in relation to pepper spot caused by Stemphylium sarciniforme

1978 ◽  
Vol 56 (20) ◽  
pp. 2491-2496 ◽  
Author(s):  
H. T. Wilkinson ◽  
R. L. Millar
Keyword(s):  
White Clover ◽  
Trifolium Repens ◽  
Fungal Colonization ◽  
Symptom Expression ◽  
Symptom Development ◽  
Cyanogenic Glucosides ◽  
Fungal Development ◽  
Cyanogenic Potential ◽  
Trifolium Repens L ◽  
Whole Mounts

White clover (Trifolium repens L.) contains two cyanogenic β-glucosides (G), linamarin and lotaustralin. Upon injury to the tissues a β-glucosidase (E) effects the release of cyanide from the β-glucosides. Four selections of white clover differing in cyanogenic properties (G+E+, G+E−, G−E+, G−E−) were examined for differences in susceptibility to Stemphylium sarciniforme. Symptom development was determined at 24, 48, 72, 96, and 120 h after the leaves were inoculated. Symptoms for all four selections consisted initially of small brown flecks (1 mm in diameter), then dark spots (1–2 mm in diameter) with definite borders, and finally senescence and wilt of the interlesion tissue. Plants containing both β-glucosidase (EC 3.2.1.21)and cyanogenic glucosides (G+E+) and those with only glucosides (G+E−) developed symptoms 24 h earlier than did the G−E+ and G−E− selections. The earliest symptoms were observed at 48 h; by 96 h all four selections showed comparable degrees of senescence and wilt. Pathogen development in infected leaves prepared as whole mounts was examined microscopically. Through 72 h after inoculation, development of S. sarciniforme in the G+E+ and G+E− selections was slower than in the G−E+ selections. By 96 h, however, fungal development in all four selections was comparable; commencement of leaf senescence coincided with extensive fungal colonization of necrotic tissue. Accelerated rates of symptom expression and retarded pathogen development apparently were positively correlated with cyanogenic potential of each white clover selection. Necrosis of suscept tissue was not correlated with cyanogenic potential of each selection.

Presymptomatic detection of Fusarium wilt of tomato by electrical resistance measurement as related to pectic enzyme production

1976 ◽  
Vol 54 (8) ◽  
pp. 752-757 ◽  
Author(s):  
Frank L. Caruso ◽  
Terry A. Tattar ◽  
Mark S. Mount ◽  
Margaret E. Malia
Keyword(s):  
Fusarium Wilt ◽  
Electrical Resistance ◽  
Wilt Disease ◽  
Symptom Development ◽  
In Vitro Production ◽  
Tomato Plants ◽  
Foliar Symptom ◽  
Vitro Production ◽  
Soil Level

Decreases in electrical resistance (ER) of tomato taproots were correlated with the progression of Fusarium wilt disease. Production of polygalacturonase (PG) from four isolates of Fusarium oxysporum f. sp. lycopersici, as determined from ammonium sulfate fractions, was correlated with the degree of virulence of each isolate. A drop in ER in tomato plant taproots at 6 cm below the soil level was noticed within 2 h after separate inoculation with all strains. These drops in ER preceded foliar symptom development by 20 h. Measurement of ER in the stems of inoculated tomato plants, however, was found to be no different from that of uninoculated plants. The rate of ER decrease was correlated with the in vitro production of PG by these isolates; the higher the PG activity, the greater the decrease in ER.

scholarly journals Effects of morning vs. evening inoculation on the development of Neonectria ditissima lesions

2018 ◽  
Vol 71 ◽  
pp. 353
Author(s):  
Emma Patrick ◽  
Anthea Garmey ◽  
Lauren Turner ◽  
Rebecca E. Campbell ◽  
Monika Walter
Keyword(s):  
Relative Humidity ◽  
Environmental Conditions ◽  
Weather Conditions ◽  
Symptom Expression ◽  
Symptom Development ◽  
Apple Trees ◽  
Successful Development ◽  
Disease Symptoms ◽  
Average Daily Temperature ◽  
Daily Relative Humidity

The study of Neonectria ditissima causing European canker in apple trees is often dependent on controlled inoculation of tree wounds and development of canker lesions. This makes the success of the initial inoculation crucial for time-efficient research. The effect of morning vs. evening inoculation on the successful development of canker lesions was investigated. Ninety-six ‘Royal Gala’ trees were inoculated on six different days (February—March 2017), which covered several different weather conditions. On each inoculation day, 16 trees were inoculated on four rasp and four picking wounds, at 10:00 and 19:00 hours. These were then assessed over the following 8 months for presence of disease symptoms. Irrespective of rain (0—4.5 mm rainfall at the day of inoculation), temperature (average daily temperature of 14.8—21.3˚C), and humidity (average daily relative humidity of 59.8—94.2% rH), neither the day nor the hour of inoculation affected symptom development. However, more inoculated wounds developed symptoms in rasp wounds (91%) than in picking wounds (63%). Under the environmental conditions tested, inoculation timing (date and hour) had little effect on N. ditissima symptom expression.

Verticillium wilt of chrysanthemum: colonization of leaves in relation to symptom development

1971 ◽  
Vol 49 (2) ◽  
pp. 181-185 ◽  
Author(s):  
R. Hall ◽  
L. V. Busch
Keyword(s):  
Verticillium Wilt ◽  
Significant Contribution ◽  
Vascular System ◽  
Symptom Expression ◽  
Rapid Rise ◽  
Symptom Development ◽  
Flower Buds ◽  
Advanced Stages ◽  
Wilt Symptom ◽  
Leaf Exudate

The vascular system of leaves of chrysanthemum plants inoculated with Verticillium dahliae was invaded by mycelium before the appearance of visible wilt symptoms. After flower buds appeared a rapid rise in the number of propagules of fungus in the leaf was followed by a rise in severity of visible wilt symptom expression and conductivity of leaf exudate. Those portions of the leaf with the most advanced stages of wilt contained the greatest amounts of fungus. It is suggested that the mycelium within the leaf makes a significant contribution to the development of symptoms of wilt.

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