scholarly journals The Effect of Wounding, Temperature, and Inoculum on the Development of Pink Rot of Potatoes Caused by Phytophthora erythroseptica

Plant Disease ◽  
2000 ◽  
Vol 84 (12) ◽  
pp. 1327-1333 ◽  
Author(s):  
B. Salas ◽  
R. W. Stack ◽  
G. A. Secor ◽  
N. C. Gudmestad
Keyword(s):  
Infection Risk ◽  
Infected Tuber ◽  
Tuber Tissue ◽  
Inoculum Level ◽  
Inoculum Sources ◽  
Pink Rot ◽  
High Inoculum ◽  
Phytophthora Erythroseptica ◽  
Laboratory Cultures ◽  
Potential Impact

The effect of wounding, temperature, and inoculum on the development of pink rot caused by Phytophthora erythroseptica, was studied for its potential impact on postharvest infection. Tissue plugs cut from pink rot infected tubers and plugs of similar size from laboratory cultures of the pathogen were highly effective inoculum sources on wounded tubers. Severe wounding, temperatures of 15 to 25°C, and high inoculum density affected the infection risk. Regardless of source or amount of inoculum, any degree of wounding greatly increased incidence of infection of tubers by P. erythroseptica. Infections in unwounded tubers started at 15°C, whereas in wounded tubers infection started at 10°C. Incidence of pink rot was high when two or three of the factors (severe wounding, high temperature, high inoculum level) were favorable. Incidence of pink rot was intermediate when only one factor was favorable. Incidence of pink rot was low or absent without a favorable factor (no wounding, low temperature, and low inoculum), Since infected tuber tissue may serve as potential inoculum source for postharvest infection of tubers by P. erythroseptica, the removal of pink rot infected tubers at harvest is desirable. Avoidance of wounding and rapid cooling of storage bins to 10°C may also help control pink rot.

scholarly journals In-Furrow Applications of Metalaxyl and Phosphite for Control of Pink Rot (Phytophthora erythroseptica) of Potato in New Brunswick, Canada

Plant Disease ◽  
2007 ◽  
Vol 91 (10) ◽  
pp. 1305-1309 ◽  
Author(s):  
Khalil I. Al-Mughrabi ◽  
Rick D. Peters ◽  
H. W. (Bud) Platt ◽  
Gilles Moreau ◽  
Appanna Vikram ◽  
...  
Keyword(s):  
New Brunswick ◽  
Disease Incidence ◽  
Field Trials ◽  
Russet Burbank ◽  
Viable Option ◽  
Potato Plants ◽  
Pink Rot ◽  
Phytophthora Erythroseptica ◽  
Sensitive Isolate ◽  
The Mean

The efficacy of metalaxyl-m (Ridomil Gold 480EC) and phosphite (Phostrol) applied at planting in-furrow against pink rot (Phytophthora erythroseptica) of potato (Solanum tuberosum) ‘Shepody’ and ‘Russet Burbank’ was evaluated in field trials conducted in 2005 and 2006 in Florenceville, New Brunswick, Canada. Inoculum made from a metalaxyl-m-sensitive isolate of P. erythroseptica from New Brunswick was applied either in-furrow as a vermiculite slurry at planting or as a zoospore drench in soils adjacent to potato plants in late August. After harvest, the number and weight of tubers showing pink rot symptoms were assessed and expressed as percentages of the total tuber number and total weight of tubers. Metalaxyl-m applied in-furrow was significantly more effective against pink rot than phosphite. The mean percentage of diseased tubers as a percentage of total tuber weight was 1.5% (2005) and 1.2% (2006) for metalaxyl-m-treated plots and 9.6% (2005) and 2.8% (2006) for phosphite-treated plots, a percentage similar to that obtained in inoculated control plots with no fungicide treatment. The mean percentage of diseased tubers expressed as a percentage of the total number of tubers was 1.7% (2005) and 1.3% (2006) for metalaxyl-m-treated plots and 10.1% (2005) and 3.1% (2006) for phosphite-treated plots. Disease incidence was significantly higher using the late-season inoculation technique (respective means in 2005 and 2006 were 9.9 and 3.8% diseased tubers, by weight, and 10.6 and 3.9%, by number) than with the in-furrow inoculation method (respective means in 2005 and 2006 were 3.3 and 0.7% by weight, and 3.7 and 1.3%, by number). The potato cv. Shepody was significantly more susceptible to pink rot (9.9 and 3.3% diseased tubers, by weight, in 2005 and 2006, respectively, and 10.6 and 3.9%, by number) than Russet Burbank (respective means in 2005 and 2006 were 3.4,% and 1.2%, by weight, and 3.7,% and 1.2%, by number). Our findings indicate that metalaxyl applied in-furrow at planting is a viable option for control of pink rot caused by metalaxyl-sensitive strains of P. erythroseptica, whereas phosphite was ineffective.

scholarly journals A Rapid Technique for the Evaluation of Potato Germ Plasm for Susceptibility to Pink Rot

Plant Disease ◽  
2001 ◽  
Vol 85 (8) ◽  
pp. 833-837 ◽  
Author(s):  
R. D. Peters ◽  
A. V. Sturz
Keyword(s):  
Prince Edward Island ◽  
Germ Plasm ◽  
Potato Cultivars ◽  
Reliable Technique ◽  
Disease Symptoms ◽  
Disease Response ◽  
Pink Rot ◽  
Phytophthora Erythroseptica ◽  
Screening Protocol ◽  
Disease Free

Disease-free plantlets of 20 potato cultivars commonly grown in Prince Edward Island were inoculated with zoospore suspensions of Phytophthora erythroseptica, the causal agent of pink rot, to determine disease response. All inoculated cultivars developed disease symptoms relative to noninoculated controls, but disease severity differed significantly (P = 0.05) among cultivars. Plantlets of the cultivars Goldrush and Yukon Gold were consistently the most susceptible to the disease, whereas plantlets of cultivars Butte and Russet Burbank were the least susceptible. Most of the cultivars assessed were moderately susceptible to disease. Plantlets of potato cultivars with late-season field maturity were more resistant to disease than those with early or mid-season maturity. Isolates of P. erythroseptica from diverse regions of Prince Edward Island and Maine did not differ significantly (P = 0.05) in pathogenicity. The screening protocol described was a reliable technique to determine the relative resistance of nontuber potato germ plasm to disease, resulting from infection with P. erythroseptica.

Expression of resistance in bean pods to an incompatible isolate of Pseudomonas syringae

1977 ◽  
Vol 55 (15) ◽  
pp. 2043-2052 ◽  
Author(s):  
D. M. Webster ◽  
L. Sequeira
Keyword(s):  
Pseudomonas Syringae ◽  
Bacterial Growth ◽  
Ethanolic Extract ◽  
Fresh Weight ◽  
Inoculum Level ◽  
Bacterial Populations ◽  
Progressive Decline ◽  
High Inoculum ◽  
Inhibitory Compounds ◽  
Extract Fraction

Isolates of Pseudomonas syringae from hairy vetch were either virulent (compatible) or avirulent (incompatible) to bean. When bean pods were injected at high inoculum levels (5 × 107 cells/ml), both compatible and incompatible isolates multiplied rapidly and caused water-soaking of injected tissues; populations of both isolates were similar at the end of log phase. Lesions caused by the incompatible isolate turned brown by 3 days after inoculation and did not expand; those caused by the compatible isolate remained water-soaked and expanded into the adjoining, noninoculated tissues. At low inoculum levels (5 × 104 cells/ml), the compatible isolate exhibited the same pattern of multiplication and lesion development as at the high inoculum level. The incompatible isolate, on the other hand, caused necrotic flecking within the injected area by 24 h, and these small lesions remained limited. Appearance of the necrotic flecks was correlated with a progressive decline in bacterial populations; after5 days, the population of incompatible bacteria was about a hundredfold lower than that of compatible ones. Populations of incompatible bacteria within and between the necrotic flecks declined rapidly, indicating the potential accumulation of inhibitors of bacterial growth as a result of an inducible resistance mechanism.The phytoalexin phaseollin reached 280 μg/g fresh weight by 3 days after inoculation of bean pods with incompatible bacteria. However, this compound was not involved in resistance. Neither compatible nor incompatible isolates of the bacterium were significantly inhibited when grown in a medium saturated with phaseollin. When other antibiotic substances in plant extracts were sought, substantial amounts of inhibitory compounds were detected only in the ethanolic extract (fraction soluble in ethyl acetate) of pods previously inoculated with an incompatible isolate of P. syringae. Only low levels of inhibition were obtained from identical extracts of uninfected pods or from pods inoculated with a compatible isolate of P. syringae. Bacterial growth was completely prevented in a bean infusion medium containing 1 g fresh weight equivalent of pod tissue challenged with the incompatible isolate. The active compound(s) was nonfluorescent, had a UV absorption maximum at 286 nm, and gave a positive reaction with reagents for phenolic compounds.

scholarly journals Effect of Application Method and Rate on Residual Efficacy of Mefenoxam and Phosphorous Acid Fungicides in the Control of Pink Rot of Potato

Plant Disease ◽  
2011 ◽  
Vol 95 (8) ◽  
pp. 997-1006 ◽  
Author(s):  
Raymond J. Taylor ◽  
Julie S. Pasche ◽  
Neil C. Gudmestad
Keyword(s):  
Irrigation System ◽  
Phosphorous Acid ◽  
Field Trials ◽  
Resistant Isolate ◽  
Challenge Inoculation ◽  
Pink Rot ◽  
Phytophthora Erythroseptica ◽  
Small Plot ◽  
Tuber Rot ◽  
Commercial Field

Experiments were conducted to examine the effectiveness of rate and method of phosphorous acid application for controlling pink rot of potato (Solanum tuberosum) caused by Phytophthora erythroseptica. Replicated small-plot and replicated split commercial field trials were established in commercial production fields in Minnesota from 2006 to 2009. Fungicides were applied in-furrow at planting, or as one, two, or three foliar applications via ground sprayer, irrigation system (chemigation), or fixed-wing aircraft. Phosphorous acid efficacy was compared to mefenoxam, the fungicide commonly utilized to manage pink rot, either by determining natural infections in the field or by inoculating eyes of harvested tubers using a mefenoxam-sensitive and -resistant isolate of P. erythroseptica via postharvest challenge inoculation. In replicated small plot trials, both in-furrow and two foliar applications of mefenoxam controlled tuber rot in the field, and significantly controlled tuber rot in storage. Phosphorous acid also reduced tuber rot in the field when applied two or three times to the foliage. Although phosphorous acid was ineffective when applied in-furrow, one, two, and three foliar applications and a postharvest application of phosphorous acid controlled mefenoxam-sensitive and -resistant isolates of P. erythroseptica during storage for 187 days, while mefenoxam failed to control the resistant isolate. In replicated split commercial field trials, two aerial applications of phosphorous acid were as effective as three applications in reducing pink rot incidence in tubers inoculated postharvest. Three aerial applications were as effective as three chemigation applications in replicated split commercial field trials in 2008, but provided significantly greater protection than chemigation in 2009.

scholarly journals Competitive Parasitic Fitness of Mefenoxam-Sensitive and -Resistant Isolates of Phytophthora erythroseptica under Fungicide Selection Pressure

Plant Disease ◽  
2011 ◽  
Vol 95 (6) ◽  
pp. 691-696 ◽  
Author(s):  
Venkataramana Chapara ◽  
Raymond J. Taylor ◽  
Julie S. Pasche ◽  
Neil C. Gudmestad
Keyword(s):  
Selection Pressure ◽  
Phosphorous Acid ◽  
In Vivo Studies ◽  
Tuber Initiation ◽  
Pink Rot ◽  
Phytophthora Erythroseptica ◽  
Parasitic Fitness ◽  
Field Plots

A 2-year field and laboratory experiment was initiated to study the competitive parasitic fitness of mefenoxam-resistant (50% effective concentration [EC50] > 100 μg ml–1) and mefenoxam-sensitive (EC50 = 0.07 μg ml–1) isolates of Phytophthora erythroseptica with equal aggressiveness. The competitive ability of the mefenoxam-resistant and -sensitive isolates was tested under no selection pressure (nonfungicide treated) as well as under the influence of mefenoxam and non-mefenoxam (phosphorous acid) fungicides. P. erythroseptica isolates were combined in four ratios of mefenoxam-resistant (R) to mefenoxam-susceptible (S) (0R:0S, 1R:1S, 3R:1S, and 1R:3S) and subsequently infested into the soil at the time of planting. In-furrow mefenoxam applications were applied to the soil immediately following infestation with P. erythroseptica. Phosphorous acid was applied at tuber initiation and 14 days after tuber initiation. Noninfested, nonfungicide-treated plots served as controls. P. erythroseptica isolates recovered from field-infected pink rot tubers at harvest and 3 to 4 weeks after harvest were tested for mefenoxam sensitivity in vitro. In vivo studies were performed by challenge inoculating a zoospore suspension in the four ratios described above onto potato tubers harvested from nontreated, phosphorous acid-treated, or mefenoxam-treated field plots. These field plots were not infested with P. erythroseptica at planting. Results from both field and in vivo studies demonstrate that mefenoxam-resistant isolates of P. erythroseptica are as fit as sensitive isolates in the absence of selection pressure or in the presence of a phosphorous acid fungicide treatment. Under mefenoxam selection pressure, mefenoxam-resistant P. erythroseptica isolates were more parasitically fit than -sensitive isolates. These studies suggest the lack of an apparent fitness penalty in mefenoxam-resistant P. erythroseptica populations under field conditions and that these isolates could be stable in most agroecological systems. Based on these results, mefenoxam-based fungicides are no longer recommended for the management of pink rot once mefenoxam-resistant P. erythroseptica populations are detected in a specific field.

scholarly journals Sensitivity of North American Isolates of Phytophthora erythroseptica and Pythium ultimum to Mefenoxam (Metalaxyl)

Plant Disease ◽  
2002 ◽  
Vol 86 (7) ◽  
pp. 797-802 ◽  
Author(s):  
R. J. Taylor ◽  
B. Salas ◽  
G. A. Secor ◽  
V. Rivera ◽  
N. C. Gudmestad
Keyword(s):  
Pythium Ultimum ◽  
Effective Management ◽  
Potato Tubers ◽  
Pink Rot ◽  
Phytophthora Erythroseptica ◽  
Disease Management Strategy ◽  
Potato Tuber Rot ◽  
Canadian Provinces ◽  
Production Areas ◽  
First Time

A 4-year study (1997 to 2000) was conducted to determine the sensitivities of the potato tuber rot pathogens, Phytophthora erythroseptica and Pythium ultimum, to mefenoxam (metalaxyl). A total of 2,277 tubers showing symptoms of “water rot” were collected from 16 states and 2 Canadian provinces. From these, 849 isolates of P. erythroseptica and 213 isolates of P. ultimum were obtained, and 805 and 190 isolates, respectively, were tested for their ability to grow on V8 medium amended at 0.01 to 100 μg/ml with fungicide. Isolates ranged widely in their responses to mefenoxam. The presence of resistant isolates (EC50 > 100 μg ml-1) of P. erythroseptica in the potato producing areas of Maine was confirmed. The presence of P. erythroseptica isolates in Idaho and Minnesota resistant to mefenoxam is reported for the first time. The proportion of P. erythroseptica isolates resistant to mefenoxam varied from 2.9 to 36.2% between 1997 and 2000. The proportion of resistant P. ultimum isolates represented only a small proportion of the isolates tested (3.7%). A single resistant P. ultimum isolate was recovered from Washington, whereas most of the resistant isolates obtained (5 of 7) were collected in Minnesota during the final year of the study. This is the first report of resistance in P. ultimum pathogenic to potato tubers. These observations suggest that pink rot and leak could become significant problems in the future, particularly in those areas where resistance has been detected. Our results have implications for the effective management of water rot. Monitoring the sensitivity of the pathogen population to mefenoxam in all production areas should be considered and integrated as a part of the overall disease management strategy.

Phytophthora erythroseptica. [Descriptions of Fungi and Bacteria].

1978 ◽  
Author(s):  
D. Jean Stamps
Keyword(s):  
Central America ◽  
Geographical Distribution ◽  
Root Rot ◽  
Pink Rot ◽  
Phytophthora Erythroseptica ◽  
Flowering Stem ◽  
Tulip Bulbs ◽  
And Storage ◽  
Rhizome Rot ◽  
Apparently Healthy

Abstract A description is provided for Phytophthora erythroseptica. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Potato, asparagus, cineraria, tomato, pea, raspberry, tulip, Zantedeschia, sugarcane, vetch. DISEASE: Pink rot of potato; shanking of tulip; rhizome rot and leaf blight of Zantedeschia; sugarcane seed-piece rot; raspberry root rot; tomato buckeye rot. GEOGRAPHICAL DISTRIBUTION: Europe (UK, Irish Republic, Belgium, Bulgaria, France, Greece, Italy, Netherlands, Poland, Switzerland, USSR, Yugoslavia); Asia (India, Indonesia, Iran); Africa (Egypt); N. America (Canada, USA); Central America (Cuba); S. America (Venezuela, Peru); Australia; New Zealand. (CMI Map 83, ed. 4, 1973). TRANSMISSION: Soil-borne, oospores disseminated from diseased potato stems and roots persisting for many years. In the field tubers are generally infected through the stolon, but direct infection through eyes may occur in field and storage under moist conditions (13, 180; 19, 40). Transmission during storage, and survival of inoculum in apparently healthy tubers, was shown to be possible (57, 758). Tulip bulbs were invaded from the soil through the roots to the basal plate and flowering stem (18, 183).

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