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.

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 Limited Genetic Diversity in North American Isolates of Phytophthora erythroseptica Pathogenic to Potato Based on RAPD Analysis

Plant Disease ◽  
2005 ◽  
Vol 89 (4) ◽  
pp. 380-384 ◽  
Author(s):  
Rick D. Peters ◽  
Rod J. Clark ◽  
Albert D. Coffin ◽  
Antony V. Sturz ◽  
David H. Lambert ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
North America ◽  
New Brunswick ◽  
Prince Edward Island ◽  
Random Amplified Polymorphic Dna ◽  
Geographic Origin ◽  
The United States ◽  
Vitro Assay ◽  
Phytophthora Erythroseptica

Pink rot of potato (Solanum tuberosum), caused by Phytophthora erythroseptica, is found wherever potatoes are grown, and in the last decade, it has reemerged as an economically important disease in Canada and the United States. A selection of isolates of P. erythroseptica from major potato-growing regions in North America, namely Prince Edward Island and New Brunswick, Canada, and Maine and Idaho, U.S.A., was assessed for genetic diversity with randomly chosen decanucleotide primers which were used to amplify regions of DNA to reveal polymorphisms among templates (random amplified polymorphic DNA [RAPD]). The isolates varied in their geographic origin as well as in their sensitivity to mefenoxam, as determined by an in vitro assay. In three separate RAPD screens (I, II, and III) with 23 isolates of P. erythroseptica chosen from a larger collection, 1,410, 369, and 316 robust, scorable bands were amplified, respectively. However, among the bands amplified in screens I, II, and III, only 3, 1, and 3 bands, respectively, were polymorphic. When three primers yielding polymorphisms were used to screen 106 isolates from Prince Edward Island and New Brunswick, or a representative collection of 32 isolates from Prince Edward Island, New Brunswick, Maine, and Idaho, no major variation was discovered. RAPD markers were not correlated with geographic origin or mefenoxam sensitivity of the isolates. From an evolutionary standpoint, the absence of genetic diversity among the isolates of P. erythroseptica we examined may be attributable to the relatively recent introduction of a small founding population of the pathogen in North America.

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 Challenges of Guarantee-Time Bias

2013 ◽  
Vol 31 (23) ◽  
pp. 2963-2969 ◽  
Author(s):  
Anita Giobbie-Hurder ◽  
Richard D. Gelber ◽  
Meredith M. Regan
Keyword(s):  
Cox Model ◽  
Disease Free Survival ◽  
Bisphosphonate Therapy ◽  
Disease Response ◽  
Breast International Group ◽  
Immortal Time Bias ◽  
Response Onset ◽  
Using Data ◽  
Disease Free

The potential for guarantee-time bias (GTB), also known as immortal time bias, exists whenever an analysis that is timed from enrollment or random assignment, such as disease-free or overall survival, is compared across groups defined by a classifying event occurring sometime during follow-up. The types of events associated with GTB are varied and may include the occurrence of objective disease response, onset of toxicity, or seroconversion. However, comparative analyses using these types of events as predictors are different from analyses using baseline characteristics that are specified completely before the occurrence of any outcome event. Recognizing the potential for GTB is not always straightforward, and it can be challenging to know when GTB is influencing the results of an analysis. This article defines GTB, provides examples of GTB from several published articles, and discusses three analytic techniques that can be used to remove the bias: conditional landmark analysis, extended Cox model, and inverse probability weighting. The strengths and limitations of each technique are presented. As an example, we explore the effect of bisphosphonate use on disease-free survival (DFS) using data from the BIG (Breast International Group) 1-98 randomized clinical trial. An analysis using a naive approach showed substantial benefit for patients who received bisphosphonate therapy. In contrast, analyses using the three methods known to remove GTB showed no statistical evidence of a reduction in risk of a DFS event with bisphosphonate therapy.

Metalaxyl sensitivity of isolates of Phytophthora erythroseptica in Prince Edward Island

2001 ◽  
Vol 50 (3) ◽  
pp. 302-309 ◽  
Author(s):  
R. D. Peters ◽  
A. V. Sturz ◽  
B. G. Matheson ◽  
W. J. Arsenault ◽  
A. Malone
Keyword(s):  
Prince Edward Island ◽  
Phytophthora Erythroseptica ◽  
Metalaxyl Sensitivity

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.

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