The Effects of Host Diversity and Other Management Components on Epidemics of Potato Late Blight in the Humid Highland Tropics

A field study at three highland sites near Quito, Ecuador, was conducted to determine whether host-diversity effects on potato late blight would be as important as recently found in studies conducted in temperate areas. We compared three potato mixtures and use of mixtures in combination with different planting densities and two fungicide regimes. Treatment comparisons were made by absolute and relative measures of host-diversity effects and incorporating a truncated area under the disease progress curve as a means of standardizing comparisons across sites. Potato-faba intercrops consisting of only 10% potato provided an estimate of the effects of dilution of susceptible host tissue. Host-diversity effects were very different across study sites, with a large host-diversity effect for reduced disease only at the site most distant from commercial potato production. Planting density had little influence on host-diversity effects or on late blight in single-genotype stands. Fungicide use in combination with potato mixtures enhanced a host-diversity effect for reduced late blight. Potato-faba intercrops produced only a small decrease in potato late blight. Effects of host diversity on yield were variable, with the greatest increase in yield for mixtures treated with fungicides at the site most distant from commercial potato production. The effects of host diversity on late blight severity may be less consistent in the tropical highlands than in the temperate zone, but can contribute to integrated disease management.

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Host Diversity Can Reduce Potato Late Blight Severity for Focal and General Patterns of Primary Inoculum

Phytopathology ◽

10.1094/phyto.2000.90.12.1307 ◽

2000 ◽

Vol 90 (12) ◽

pp. 1307-1312 ◽

Cited By ~ 42

Author(s):

K. A. Garrett ◽

C. C. Mundt

Keyword(s):

Late Blight ◽

Tuber Yield ◽

Statistical Significance ◽

Experimental System ◽

Potato Late Blight ◽

Management Tools ◽

Host Diversity ◽

Progress Curve ◽

Single Genotype ◽

Diversity Effects

The use of host diversity as a tool for management of potato late blight has not been viewed as promising in the past. But the increasing importance of late blight internationally has brought new consideration to all potential management tools. We studied the effect of host diversity on epidemics of potato late blight in Oregon, where there was little outside inoculum. The experimental system consisted of susceptible potato cv. Red LaSoda and a highly resistant breeding selection, inoculated with local isolates of US-8 Phytophthora infestans. Potatoes were grown in single-genotype plots and also in a mixture of 10 susceptible and 26 resistant potato plants. Half of the plots received inoculation evenly throughout the plot (general inoculation) and half received an equal quantity of inoculum in only one corner of the plot (focal inoculation). The area under the disease progress curve (AUDPC) was greater in single genotype stands of susceptible cv. Red LaSoda inoculated throughout the plot than with stands inoculated in one focus. The host-diversity effect on foliar late blight was significant in both years of the investigation; the AUDPC was reduced by an average of 37% in 1997 and 36% in 1998, compared with the mean disease level for the potato genotypes grown separately. Though the evidence for influence of inoculum pattern on host-diversity effects was weak (P = 0.15), in both years there was a trend toward greater host-diversity effects for general inoculation. Statistical significance of host-diversity effects on tuber yield and blight were found only in one of the two years. In that year, tuber yield from both the resistant and susceptible cultivar was increased in mixtures compared with single genotype stands and tuber blight was decreased in mixtures for susceptible cv. Red LaSoda.

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Ametoctradin: a new fungicide for potato late blight control

Arquivos do Instituto Biológico ◽

10.1590/1808-1657000352014 ◽

2016 ◽

Vol 83 (0) ◽

Cited By ~ 1

Author(s):

Jesus Guerino Töfoli ◽

Ricardo José Domingues ◽

Walter Jacobelis Jr. ◽

Marina Pacheco Lombardi Tortolo

Keyword(s):

Late Blight ◽

Block Design ◽

Potato Late Blight ◽

Significant Control ◽

Progress Curve ◽

Randomized Block Design ◽

Commercial Potato ◽

Crop Development ◽

Potato Crops ◽

Application Volume

ABSTRACT: Late blight (Phytophthora infestans ) is among the most important and destructive diseases in potato cultivation. Aiming to evaluate the efficacy of the new fungicide ametoctradin, mixed with dimethomorph and metiram, an experiment was carried out in commercial potato crops (Ágata cultivar) in Pilar do Sul, São Paulo state, Brazil, during the growing season in 2013. A randomized block design was used, with 4 replications, on plots of 15 m2. Applications were carried out using a backpack sprayer with a spray-bar under 3 bar of constant pressure. The application volume varied from 300 L to 600 L.ha-1 based on crop development. The variables evaluated were leaf severity (0 to 100%), area under the disease progress curve, and yield. Ametoctradin + dimethomorph (1.25 L.ha-1) provided significant control of late blight, exceeding benthiavalicarb + fluazinam, dimethomorph + metiram, dimethomorph + pyraclostrobin, cymoxanil + mancozeb, metalaxyl-M + mancozeb, ametoctradin + metiram, and pyraclostrobin + metiram, although similar to ametoctradin + dimethomorph (1.00 L.ha-1), fluopicolide + propamocarb, and fenamidone + propamocarb. Ametoctradin + metiram resulted in moderate control, which was always similar to the standard. Ametoctradin and its associations represent a new alternative for the management of potato late blight.

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Yield and resistance of potato cultivars with colour flesh to potato late blight

Plant Soil and Environment ◽

10.17221/371/2017-pse ◽

2017 ◽

Vol 63 (No. 7) ◽

pp. 328-333

Author(s):

Pazderů Kateřina ◽

Hamouz Karel

Keyword(s):

Late Blight ◽

Field Experiments ◽

Potato Late Blight ◽

Russet Burbank ◽

Weak Dependence ◽

Potato Cultivars ◽

Disease Progress Curve ◽

Disease Progress ◽

Progress Curve ◽

Better Than

The resistance to potato late blight (as AUDPC – the area under the disease progress curve) and yield were evaluated in precise field experiments with 13 colour-fleshed potato cultivars. Red Emmalie and Blaue Anneliese were the most profitable cultivars of potatoes with coloured flesh, the overall yield did not differ statistically from the control cv. Agria. Cv. Blaue Anneliese resistance to potato late blight was considerably better than both control cultivars, other 2 cultivars HB Red and Red Emmalie were similar to cv. Agria. Surprisingly, cv. Russet Burbank was found to be more resistant than most cultivars tested. A statistically significant weak dependence (r = 0.36) between the percentage of infestation of plants in the T6 evaluation date (6–8 August in individual years) and the yield was detected, the slightly stronger (r = 0.40) was the correlation between AUDPC values and total yields.

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Effects of Planting Density and the Composition of Wheat Cultivar Mixtures on Stripe Rust: An Analysis Taking into Account Limits to the Replication of Controls

Phytopathology ◽

10.1094/phyto.2000.90.12.1313 ◽

2000 ◽

Vol 90 (12) ◽

pp. 1313-1321 ◽

Cited By ~ 21

Author(s):

K. A. Garrett ◽

C. C. Mundt

Keyword(s):

Stripe Rust ◽

Plant Density ◽

Puccinia Striiformis ◽

Planting Density ◽

Host Diversity ◽

Diversity Effect ◽

Single Genotype ◽

Unique Pair ◽

Single Host ◽

Rust Severity

The effect of plant density on disease is not well understood in populations of a single host plant genotype and has been studied even less in mixtures of host genotypes. We performed an experiment to evaluate the effect of wheat planting density on infection by Puccinia striiformis in experimental plots with a single wheat genotype and in plots with two genotypes making up a range of frequencies. Stripe rust severity in single-genotype plots increased with planting density in 1997 but decreased with planting density in 1998. Disease in host mixtures was compared to the weighted mean of disease levels in the corresponding single-genotype plots. The design of the field experiment included limited replication of these reference treatments (that is, there was not a unique pair of single-genotype plots for each mixture plot); therefore, we devised an analysis based on collapsing the data into independent mean observations. Disease reduction due to host diversity was less when one genotype predominated than when both host genotypes were present at nearly equal frequencies. The greatest mean host-diversity effect for reduced disease was at the intermediate planting density of 250 seeds per m2.

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Can Weed Hosts Increase Aggressiveness of Phytophthora infestans on Potato?

Phytopathology ◽

10.1094/phyto-07-11-0192 ◽

2012 ◽

Vol 102 (4) ◽

pp. 429-433 ◽

Cited By ~ 19

Author(s):

L. Grönberg ◽

B. Andersson ◽

J. Yuen

Keyword(s):

Late Blight ◽

Phytophthora Infestans ◽

Genotypic Variation ◽

Latency Period ◽

Potato Production ◽

Potato Late Blight ◽

Hairy Nightshade ◽

Weed Hosts ◽

Lesion Growth ◽

Sporulation Capacity

Potato late blight, caused by Phytophthora infestans, is a major disease in potato production throughout the world. In southern Sweden, hairy nightshade (Solanum physalifolium), an alternative non-crop host to the pathogen, is an increasing weed problem. Single-lesion leaves infected by P. infestans were collected from potato and hairy nightshade to determine phenotypic and genotypic population differentiation of P. infestans between the two hosts. Genotypic variation was estimated using microsatellites as markers. The results showed no genotypic differentiation in the samples between the two hosts. Aggressiveness tests were performed using the sampled isolates to cross-inoculate potato and hairy nightshade. The proportion of infected leaves, latency period, lesion growth rate, and sporulation capacity were measured. For isolates from hairy nightshade, the odds of infection were higher on both hosts combined. When tested on potato leaves, isolates from hairy nightshade showed a significantly shorter latency period and higher sporulation capacity compared with isolates from potato. This indicates that an alternative host can filter populations of P. infestans toward a higher aggressiveness, which could lead to increasing problems in controlling potato late blight.

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Association of Solar Irradiance and Days of Precipitation with Incidence of Potato Late Blight in the Semiarid Environment of the Columbia Basin

Plant Disease ◽

10.1094/pdis-93-3-0272 ◽

2009 ◽

Vol 93 (3) ◽

pp. 272-280 ◽

Cited By ~ 8

Author(s):

Dennis A. Johnson ◽

Thomas F. Cummings ◽

Rita Abi Ghanem ◽

J. Richard Alldredge

Keyword(s):

Late Blight ◽

Solar Irradiance ◽

Meteorological Data ◽

Potato Late Blight ◽

Multiple Regression Model ◽

Columbia Basin ◽

South Central ◽

Commercial Potato ◽

First Occurrence ◽

Rainy Days

The effects of cumulative solar irradiance and rainfall on incidence of potato late blight (caused by Phytophthora infestans) in the Columbia Basin of south-central Washington and north-central Oregon were investigated using meteorological data collected near Othello, WA from 1990 through 2007 and Prosser, WA from 1990 through 2006. An association between solar irradiance and seasonal differences in late blight epidemics has not been quantitatively determined. Incidence of late blight in the Columbia Basin significantly increased as cumulative solar irradiance decreased during 1 April to 31 July and 1 June to 31 July at both Othello and Prosser. Incidence of late blight also increased as number of rainy days increased during 1 April to 31 July at Othello and Prosser and from 1 June to 31 July at Prosser. Coefficients of determination for significant models on late bight incidence ranged from 0.28 to 0.43 for cumulative solar irradiance and 0.27 to 0.38 for number of rainy days. Late blight incidence significantly increased as day of the year for first occurrence of late blight decreased in the Columbia Basin. A multiple regression model that included cumulative solar irradiance from 1 June to 31 July at Prosser and day of year for first occurrence of late blight as independent variables accounted for 58% of the variation for late blight incidence (adjusted R2 = 0.58), and a model that included number of cloudy days without rain combined with number of rainy days accounted for 62% of the variation for late blight incidence. This is the first report demonstrating a quantitative association of solar irradiance and incidence of late blight in commercial potato fields.

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Epidemiology in Mixed Host Populations

Phytopathology ◽

10.1094/phyto.1999.89.11.984 ◽

1999 ◽

Vol 89 (11) ◽

pp. 984-990 ◽

Cited By ~ 186

Author(s):

K. A. Garrett ◽

C. C. Mundt

Keyword(s):

Plant Competition ◽

Natural Populations ◽

Host Density ◽

Host Population ◽

Host Genotype ◽

Susceptible Host ◽

Disease Epidemiology ◽

Host Diversity ◽

Classic Model ◽

Diversity Effects

Although plant disease epidemiology has focused on populations in which all host plants have the same genotype, mixtures of host genotypes are more typical of natural populations and offer promising options for deployment of resistance genes in agriculture. In this review, we discuss Leonard's classic model of the effects of host genotype diversity on disease and its predictions of disease level based on the proportion of susceptible host tissue. As a refinement to Leonard's model, the spatial structure of host and pathogen population can be taken into account by considering factors such as autoinfection, interaction between host size and pathogen dispersal gradients, lesion expansion, and host carrying capacity for disease. The genetic composition of the host population also can be taken into account by considering differences in race-specific resistance among host genotypes, compensation, plant competition, and competitive interactions among pathogen genotypes. The magnitude of host-diversity effects for particular host-pathogen systems can be predicted by considering how the inherent characteristics of a system causes it to differ from the assumptions of the classic model. Because of the limited number of studies comparing host-diversity effects in different systems, it is difficult at this point to make more than qualitative predictions. Environmental conditions and management decisions also influence host-diversity effects on disease through their effect on factors such as host density and epidemic length and intensity.

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Pathogens which threaten food security: Phytophthora infestans, the potato late blight pathogen

Food Security ◽

10.1007/s12571-021-01141-3 ◽

2021 ◽

Author(s):

Jonathan Yuen

Keyword(s):

Late Blight ◽

Phytophthora Infestans ◽

Large Scale ◽

Plant Disease ◽

Plant Pathogens ◽

Potato Production ◽

Potato Late Blight ◽

Developed Countries ◽

History Of ◽

Late Blight Pathogen

AbstractPotato late blight, caused by Phytophthora infestans, is a critical disease of potato and other solanaceous crops, such as tomato. The history of late blight is, in some ways, the history of modern plant pathology. It received much attention in the mid 1800’s by causing the Irish potato famine, and the pathogen played a prominent role in the development of the concept of plant disease and plant pathogens. The pathosystem has also been important in the development of pesticides that are active against plant pathogens, and has also been a model system in understanding concepts ranging from cellular processes, such as how resistance to plant pathogens functions, to large scale processes, such as implementation of regional plant disease warning systems. P.infestans has a secured a place in modern potato production, both in developed and less-developed countries.

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Effect of Host Plant Resistance and Reduced Rates and Frequencies of Fungicide Application to Control Potato Late Blight

Plant Disease ◽

10.1094/pdis.2001.85.10.1113 ◽

2001 ◽

Vol 85 (10) ◽

pp. 1113-1118 ◽

Cited By ~ 33

Author(s):

W. W. Kirk ◽

K. J. Felcher ◽

D. S. Douches ◽

J. Coombs ◽

J. M. Stein ◽

...

Keyword(s):

Late Blight ◽

Field Experiments ◽

Potato Late Blight ◽

Application Rate ◽

Effective Control ◽

Michigan State University ◽

State University ◽

Breeding Lines ◽

Application Rates ◽

Commercial Potato

Field experiments were conducted during 1998 to 2000 to determine the response of commercial potato cultivars and advanced breeding lines (ABL) differing in susceptibility to foliar late blight (caused by Phytophthora infestans) to reduced rates and frequencies of residual, contact fungicide applications. When environmental conditions were most favorable for the development of late blight, the lowest application rate of the fungicides chlorothalonil or fluazinam (33% of the manufacturers' recommended application rate [MRAR]) gave unsatisfactory control of potato late blight. Under conditions moderately conducive for late blight development, effective control was achieved with 33 to 66% MRAR with either fungicide. The Michigan State University advanced selection, MSG274-3, was the least susceptible ABL tested and, during 1998 to 2000, late blight was effectively managed using reduced rates of fungicides. Application rates of chlorothalonil (33 to 100% MRAR) significantly reduced late blight in the cultivar Snowden (5-day application interval) compared with the nontreated control; whereas, late blight was not effectively controlled in Snowden even at 100% MRAR of chlorothalonil at either 10- or 15-day application intervals in 1999 or 2000. The ABL MSG274-3 was the least susceptible of all cultivars and ABL used in this study, and required minimal chemical protection against late blight. The study demonstrates that ABL with reduced susceptibility to late blight can be managed with reduced fungicide rates and longer application intervals, thus offering more economical control of this disease.

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