The effect of foliar infection by Colletotrichum coccodes on yield of Russet Burbank potato was i... more The effect of foliar infection by Colletotrichum coccodes on yield of Russet Burbank potato was investigated in the greenhouse and field. Foliage of plants in both the greenhouse and field was wounded with sterile sand blown from a sandblaster before inoculation with a spore suspension of C. coccodes. In two experiments in the greenhouse, total yield was significantly reduced by 32 and 19% and mean tuber weight was significantly reduced by 29 and 43%, respectively. In the field, total tuber weight was significantly reduced by 7% in 1991, 12% in 1992, and 11% in 1993. Weights of potatoes graded U.S. No. 1 were significantly reduced by 12% in 1991, 18% in 1992, and 16% in 1993. The number of No. 1 tubers per plant was significantly reduced in the field
Dark brown to black lesions developed on leaves, petioles, and stems of Russet Burbank potato aft... more Dark brown to black lesions developed on leaves, petioles, and stems of Russet Burbank potato after wounding by sandblasting and inoculating with either conidia or sclerotia of Colletotrichum coccodes in the greenhouse and with conidia in the field. Conidia from 10 isolates and four collections of sclerotia of C. coccodes from various areas of Washington and Idaho were pathogenic on potato foliage. Significantly (P<0.01) more lesions developed on foliage that was wounded than on foliage that was not wounded just before inoculation (.)
Inferences about Verticillium dahliae are often deduced from experiments where hosts are inoculat... more Inferences about Verticillium dahliae are often deduced from experiments where hosts are inoculated with one isolate. The assumption that the outcomes from these experiments scale with V. dahliae diversity is untested. The objectives of this research were to test the hypotheses that (i) coinoculation with combinations of isolates affects plant biomass, disease expression, and fungal colonization; and (ii) hosts select for the specific isolates. Potato, mustard, and barley plants were coinoculated with seven combinations of three isolates. Genotypes recovered from infected plants were genotyped with microsatellite markers. Disease expression and fungal colonization but not plant biomass of potato was affected by coinoculation (F = 7.07, P < 0.0001; F = 2.36, P = 0.0427) and depended on the isolates with which plants were inoculated. One genotype was disproportionately selected for by all hosts. Putative heterokaryons were recovered from mustard plants coinoculated with isolates of different vegetative compatibility groups (VCG). These results support the assumption that mixed infections have marginal impacts on plant biomass but challenge the assumption that they do not affect disease expression and fungal colonization. Finally, this research provides evidence that plants select for specific V. dahliae genotypes and isolates from different VCGs can anastomose in planta.
Journal of visualized experiments : JoVE, Feb 23, 2018
On-site diagnosis of plant diseases can be a useful tool for growers for timely decisions enablin... more On-site diagnosis of plant diseases can be a useful tool for growers for timely decisions enabling the earlier implementation of disease management strategies that reduce the impact of the disease. Presently in many diagnostic laboratories, the polymerase chain reaction (PCR), particularly real-time PCR, is considered the most sensitive and accurate method for plant pathogen detection. However, laboratory-based PCRs typically require expensive laboratory equipment and skilled personnel. In this study, soil-borne pathogens of potato are used to demonstrate the potential for on-site molecular detection. This was achieved using a rapid and simple protocol comprising of magnetic bead-based nucleic acid extraction, portable real-time PCR (fluorogenic probe-based assay). The portable real-time PCR approach compared favorably with a laboratory-based system, detecting as few as 100 copies of DNA from Spongospora subterranea. The portable real-time PCR method developed here can serve as an a...
Genotyping-by-sequencing (GBS) was performed on 257 Phytophthora infestans isolates belonging to ... more Genotyping-by-sequencing (GBS) was performed on 257 Phytophthora infestans isolates belonging to four clonal lineages to study within-lineage diversity. The four lineages used in the study were US-8 (n = 28), US-11 (n = 27), US-23 (n = 166), and US-24 (n = 36), with isolates originating from 23 of the United States and Ontario, Canada. The majority of isolates were collected between 2010 and 2014 (94%), with the remaining isolates collected from 1994 to 2009, and 2015. Between 3,774 and 5,070 single-nucleotide polymorphisms (SNPs) were identified within each lineage and were used to investigate relationships among individuals. K-means hierarchical clustering revealed three clusters within lineage US-23, with US-23 isolates clustering more by collection year than by geographic origin. K-means hierarchical clustering did not reveal significant clustering within the smaller US-8, US-11, and US-24 data sets. Neighbor-joining (NJ) trees were also constructed for each lineage. All four NJ...
A water extract from the bark of guar roots inhibited germination of conidia and growth of myceli... more A water extract from the bark of guar roots inhibited germination of conidia and growth of mycelia of several plant pathogenic fungi. Germination of conidia and growth of mycelia of other test fungi were either stimulated or not affected by the extract. Fewer sclerotia were produced by Phymatotrichum omnivorum in soil with the extract than in soil without the extract.
Accuracy of prediction was analyzed for 17- and 30-day rain forecasts at two locations in the Col... more Accuracy of prediction was analyzed for 17- and 30-day rain forecasts at two locations in the Columbia Basin to determine whether forecasts were sufficiently accurate to be included as a model component to schedule fungicide applications for potato late blight. Accuracy was partitioned into specificity (percentage of forecasted nonrainfall events classified correctly) and sensitivity (percentage of forecasted daily rainfall events classified correctly). An adjusted sensitivity, which included the forecasted rain day plus the next 2 days, was also used to give a wider target than only 1 day for evaluating accuracy of forecasted rain events. For 17-day forecasts, specificity during the seasonal test period was ≥70% from mid-June through September and specificity over the days of the forecast was >70% for the first 8 days at both locations both years. Adjusted sensitivity over days of the forecast was initially >80% and then decreased as forecasts increased from 7 to 17 days for ...
The effect of foliar infection by Colletotrichum coccodes on yield of Russet Burbank potato was i... more The effect of foliar infection by Colletotrichum coccodes on yield of Russet Burbank potato was investigated in the greenhouse and field. Foliage of plants in both the greenhouse and field was wounded with sterile sand blown from a sandblaster before inoculation with a spore suspension of C. coccodes. In two experiments in the greenhouse, total yield was significantly reduced by 32 and 19% and mean tuber weight was significantly reduced by 29 and 43%, respectively. In the field, total tuber weight was significantly reduced by 7% in 1991, 12% in 1992, and 11% in 1993. Weights of potatoes graded U.S. No. 1 were significantly reduced by 12% in 1991, 18% in 1992, and 16% in 1993. The number of No. 1 tubers per plant was significantly reduced in the field
Dark brown to black lesions developed on leaves, petioles, and stems of Russet Burbank potato aft... more Dark brown to black lesions developed on leaves, petioles, and stems of Russet Burbank potato after wounding by sandblasting and inoculating with either conidia or sclerotia of Colletotrichum coccodes in the greenhouse and with conidia in the field. Conidia from 10 isolates and four collections of sclerotia of C. coccodes from various areas of Washington and Idaho were pathogenic on potato foliage. Significantly (P<0.01) more lesions developed on foliage that was wounded than on foliage that was not wounded just before inoculation (.)
Inferences about Verticillium dahliae are often deduced from experiments where hosts are inoculat... more Inferences about Verticillium dahliae are often deduced from experiments where hosts are inoculated with one isolate. The assumption that the outcomes from these experiments scale with V. dahliae diversity is untested. The objectives of this research were to test the hypotheses that (i) coinoculation with combinations of isolates affects plant biomass, disease expression, and fungal colonization; and (ii) hosts select for the specific isolates. Potato, mustard, and barley plants were coinoculated with seven combinations of three isolates. Genotypes recovered from infected plants were genotyped with microsatellite markers. Disease expression and fungal colonization but not plant biomass of potato was affected by coinoculation (F = 7.07, P < 0.0001; F = 2.36, P = 0.0427) and depended on the isolates with which plants were inoculated. One genotype was disproportionately selected for by all hosts. Putative heterokaryons were recovered from mustard plants coinoculated with isolates of different vegetative compatibility groups (VCG). These results support the assumption that mixed infections have marginal impacts on plant biomass but challenge the assumption that they do not affect disease expression and fungal colonization. Finally, this research provides evidence that plants select for specific V. dahliae genotypes and isolates from different VCGs can anastomose in planta.
Journal of visualized experiments : JoVE, Feb 23, 2018
On-site diagnosis of plant diseases can be a useful tool for growers for timely decisions enablin... more On-site diagnosis of plant diseases can be a useful tool for growers for timely decisions enabling the earlier implementation of disease management strategies that reduce the impact of the disease. Presently in many diagnostic laboratories, the polymerase chain reaction (PCR), particularly real-time PCR, is considered the most sensitive and accurate method for plant pathogen detection. However, laboratory-based PCRs typically require expensive laboratory equipment and skilled personnel. In this study, soil-borne pathogens of potato are used to demonstrate the potential for on-site molecular detection. This was achieved using a rapid and simple protocol comprising of magnetic bead-based nucleic acid extraction, portable real-time PCR (fluorogenic probe-based assay). The portable real-time PCR approach compared favorably with a laboratory-based system, detecting as few as 100 copies of DNA from Spongospora subterranea. The portable real-time PCR method developed here can serve as an a...
Genotyping-by-sequencing (GBS) was performed on 257 Phytophthora infestans isolates belonging to ... more Genotyping-by-sequencing (GBS) was performed on 257 Phytophthora infestans isolates belonging to four clonal lineages to study within-lineage diversity. The four lineages used in the study were US-8 (n = 28), US-11 (n = 27), US-23 (n = 166), and US-24 (n = 36), with isolates originating from 23 of the United States and Ontario, Canada. The majority of isolates were collected between 2010 and 2014 (94%), with the remaining isolates collected from 1994 to 2009, and 2015. Between 3,774 and 5,070 single-nucleotide polymorphisms (SNPs) were identified within each lineage and were used to investigate relationships among individuals. K-means hierarchical clustering revealed three clusters within lineage US-23, with US-23 isolates clustering more by collection year than by geographic origin. K-means hierarchical clustering did not reveal significant clustering within the smaller US-8, US-11, and US-24 data sets. Neighbor-joining (NJ) trees were also constructed for each lineage. All four NJ...
A water extract from the bark of guar roots inhibited germination of conidia and growth of myceli... more A water extract from the bark of guar roots inhibited germination of conidia and growth of mycelia of several plant pathogenic fungi. Germination of conidia and growth of mycelia of other test fungi were either stimulated or not affected by the extract. Fewer sclerotia were produced by Phymatotrichum omnivorum in soil with the extract than in soil without the extract.
Accuracy of prediction was analyzed for 17- and 30-day rain forecasts at two locations in the Col... more Accuracy of prediction was analyzed for 17- and 30-day rain forecasts at two locations in the Columbia Basin to determine whether forecasts were sufficiently accurate to be included as a model component to schedule fungicide applications for potato late blight. Accuracy was partitioned into specificity (percentage of forecasted nonrainfall events classified correctly) and sensitivity (percentage of forecasted daily rainfall events classified correctly). An adjusted sensitivity, which included the forecasted rain day plus the next 2 days, was also used to give a wider target than only 1 day for evaluating accuracy of forecasted rain events. For 17-day forecasts, specificity during the seasonal test period was ≥70% from mid-June through September and specificity over the days of the forecast was >70% for the first 8 days at both locations both years. Adjusted sensitivity over days of the forecast was initially >80% and then decreased as forecasts increased from 7 to 17 days for ...
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