Progress 10/01/03 to 09/30/07
Outputs
This paragraph contains outputs specific to the final year according to each of the four objectives. i) disease forecasting. A program to link our computer simulator of potato late blight with national weather system forecasts was developed to operate on a PC. This system is designed to enable pest managers to predict the effect of various disease management tactics using future weather. The system is currently being transferred to an internet-basis. ii) aid the breeding of resistant plants. Resistance to Phytophthora infestans in the wild tomato species, Lycopersicon pennellii, was discovered, and located as a QTL on chromosome 6. This resistance was not conditioned by maturity, and contributed about 25% of the total variance for resistance. A gene profiling experiment conducted in the field identified more than 400 genes that were differentially regulated in near-isogenic lines of tomato that differed by the portion of the chromosome containing this QTL. Eleven genes
that were differentially expressed within the first 12 h after inoculation were selected for gene silencing via VIGS (Virus Induced Gene Silencing), and these experiments are currently in progress. iii) improve the use of biobased inducers of host resistance. We detected 13 candidate genes in tomatoes that are responsive to BTH, an inducer of resistance. Silencing of several of three candidates via VIGS has not revealed a phenotype. QTLs for resistance in a tetraploid breeding population from the Cornell potato breeding were discovered. iv) Viruses were discovered in P. infestans - the first report of viruses in this species. The impact of viruses on the biology of this pathogen is now being investigated. This paragraph summarizes outputs during the life of the project: i) Disease forecasting. The computer simulator of late blight was improved to the extent that it can be used in real-time as an aid for scheduling fungicides. The programming to support this application is currently in
progress. Description of this approach has been provided to potato growers in NY at a field meeting. ii) QTLs for resistance in potatoes and tomatoes were discovered, and several of these are of sufficient magnitude to be useful in a breeding program. The QTLs in potato have been identified in a very successful family in the Cornell breeding program. iii) Inducers of host resistance to late blight were very effective in petunia, and slightly effective in tomato. The magnitude of effect in petunia is easily useful in practical disease management. iv) Biocontrols in soils. Soils from central Mexico were assayed for potential biocontrols, but these soils did not prove any more suppressive than New York soils. Viruses of P. infestans were discovered. Their potential in biocontrol is being investigated. In addition to presentation of results at meetings, the project resulted in 12 papers in refereed journals, one book chapter, and more than a dozen presentations at various grower and
scientific meetings.
Impacts
i) Disease forecasting: The improvement of the computer simulator of the late blight disease (output of this project) has enabled a new approach to disease management. We are currently accomplishing the necessary programming to put the improved simulator on the web, so that it can be used in real time as a decision aid. The grower will input historical weather data for the crop in question, and then the program will automatically obtain the national weather forecast for the next 3-5 days and predict late blight development. The program will be interactive so that grower can evaluate the impact of different management scenarios, and make a final decision based on that input. ii) Late blight resistant tomatoes and potatoes. The resistances discovered in tomatoes and potatoes are all linked to molecular markers so that they are useful in marker assisted breeding. The QTL in tomatoes is large enough to of interest to a breeder. The QTLs in the tetraploid potato breeding
population will enable the inclusion of late blight resistance in that population - a population that has already produced some promising clones. iii) Bio-based inducers of resistance. The discovery that BTH (which induces Systemic Acquired Resistance) is very effective in petunias to suppress late blight introduces an entirely new bio-based approach to managing late blight in the greenhouse. Because tomatoes and petunias are often produced in the same greenhouse, application of BTH to petunias will help protect tomatoes (the more susceptible and more vulnerable crop) from late blight. Additionally, we determined that phosphonates can contribute to suppression of late blight induced in tubers before harvest. Additional experiments are required to optimize this group of green fungicides. iv) Biocontrols of P. infestans. While we were unable to provide evidence of biocontrol agents from Mexican soils, we did discover viruses in P. infestans. The report of these viruses constitutes the
first report of a virus in this oomycete. The impact of the viruses is not yet clear, but their discovery makes possible another possibility for biocontrol. We are currently investigating the effect of these viruses on the ecology and pathogenicity of P. infestans.
Publications
- Smart, C. D., Tanksley, S. D., Mayton, H. and Fry, W. E. 2007. Resistance to Phytophthora infestans in Lycopersicon pennellii. Plant Disease 91(8): 1045-1049.
- Cai, G., Myers, K., Hillman, B. and Fry, W. E. 2007. Viruses in Phytophthora infestans, the late blight pathogen. Phytopathology 97: S16. .
- Zody, M. C., Jiang, R. H. Y., Handsaker, R., Grabherr, M., Kodira, C. D., Govers, F., Birch, P., Whisson, S., Win, J., Judelson, H. S., Ristaino, J. B., Fry, W. E., Kamoun, S. and Nusbaum, C. 2007. Genome dynamics in the pathogen/host arms race: initial analysis of the Phytophthora infestans genome. Phytopathology 97: S146.
- Restrepo, S., Fry, W. E. and Smart, C. D. 2004. Understanding the potato Phytophthora infestans compatible interaction. Phytopathology 94: S87.
- Becktell, M. C., Daughtrey, M. L. and Fry, W. E. 2003. Temperature and moisture requirements for establishment, incubation period, latent period, and sporulation of Phytophthora infestans on petunia. Phytopathology 93: S7.
- Mizubuti, E. S. G. and Fry, W. E. 2006. Potato Late Blight. The epidemiology of Plant Diseases. B. M. Cooke, D. G. Jones and B. Kaye. the Netherlands, Springer: 445-471.
|
Progress 01/01/06 to 12/31/06
Outputs
Several different phosphonate biopesticides were evaluated in three different field trials over two years for efficacy in suppressing potato late blight caused by Phytophthora infestans. Foliar disease was assessed during the growing season, and tuber disease was assessed at harvest and (for two trials) after two months in storage. The phosphonates were Biophos (dipotassium phosphonate, and dipotassium phosphate), Fosphite (mono- and dipotassium phosphonate), Prophyt (potassium phosphite), Phostrol (mono- and dibasic sodium, potassium, and ammonium phosphites), and Aliette (aluminum tris (O-ethyl phosphonate). Each phosphonate was applied at weekly intervals. Additionally some phosphonates were applied in combination wth, or in alternation with the conventional fungicide Bravo WS. All phosphonates applied alone or in combination with Bravo WS suppressed foliar disease. Although tuber blight was highly variable in these small plots, tubers from plots treated with
phosphonates generally had less tuber blight relative to tubers from plots treated with Bravo WS. The effect on tuber blight was particularly visible after two months in storage. The central highlands of Mexico are considered to be the center of diversity for Phytophthora infestans. Both mating types are known to co-habit in these regions. Cultivated potatoes and wild Solanum species are commonly infected with P. infestans in these mountain regions. We sampled three mountain and two valley soils in the Mexican central highlands and evaluated them for their suppressive activity on P. infestans. A New York soil was used for comparative analysis. Even though both mating types co-habit in the region where the soils were sampled, no oospores were found in the soil samples. Through detached leaflet infectivity bioassays, we determined that sporangia could survive and remain infective for several weeks in these soils. No significant differences were observed among the three mountain and two
valley soils from Mexico and the New York soil in terms of their influence on the survival and infectivity of P. infestans. Terminal restriction fragment length polymorphism analysis (T-RFLP) of the bacterial communities present in these soils was conducted in conjunction with the detached leaflet bioassays with the goal of characterizing the composition of potentially-suppressive soil bacterial communities and identifying possible antagonists to P. infestans. Bacterial community compositions were similar in the two Mexican valley soils, but differed substantially from those in the mountain and New York soils. The New York soil shared some population characteristics in common with both groups of Mexican soils, but it clustered separately in most analyses.
Impacts
Our discovery this past year, that pre-harvest drench applications of certain phosphonates can suppress tuber blight when foliage of the potatoes is infected, is potentially a very important discovery. Large amounts of fungicide are applied to foliage under the assumption that if there is no late blight in foliage, there will also not be any in the tubers. Unfortunately, it is very difficult to assure that there is no blight in the foliage, and in some years it is impossible to achieve that situation. If drench applications of phosphonates can protect tubers from late blight, then the need to apply very large amounts of other fungicides to the foliage will be significantly lessened. Two important benefits will result: 1) less fungicide will be released to the environment; and 2) losses due to tuber blight will be lessened. In order to evaluate this potential benefit in production agriculture, additional experiments need to be done. The realization that petunias and
calibrachoas can be sources of inoculum for the tomato and potato late blight pathogen, adds an additional management option to the suppression of tomato and potato late blight in areas where all these crops are grown in proximity such as in parts of Florida during the winter production season. We plan to investigate petunias and calibrachoas as sources of the pathogen under production conditions. If these crops are sources, mitigation techniques applied to these crops will lessen the need for fungicide on potatoes and tomatoes.
Publications
- Becktell, M.C., C.D. Smart, C.H. Haney and W.E. Fry. 2006. Host-pathogen interactions between Phytophthora infestans and the solanaceous hosts Calibrachoa x hybridus, Petunia x hybrida and Nicotiana benthamiana. Plant Disease 90: 24-32
- Rauscher, G.M., C.D. Smart, I. Simko, M. Bonierbale, H. Mayton, A. Greenland , W.E. Fry. 2006. Characterization and mapping of RPi-ber, a novel potato late blight resistance gene from Solanum berthaultii. Theor Appl Genet 112: 674-687
- Grunwald, N.J., Sturbaum, A.K., Montes, G.R., Serrano, E.G., Lozoya-Saldana, H. and Fry, W.E. 2006. Selection for fungicide resistance within a growing season in field populations of Phytophthora infestans at the center of origin. Phytopathology 96 1397-1403.
|
Progress 01/01/05 to 12/31/05
Outputs
Significant accomplishment on several fronts was concluded in 2005. We identified that petunias and calibrachoas could be hosts of Phytophthora infestans, and that these hosts could be sources of inoculum in a potato or tomato growing areas. We identified the conditions in which P. infestans was likely to infect and sporulate from infected petunias. While petunias are much less susceptible than are tomatoes or potatoes, they can be infected and (as we demonstrated) they can be sources of inoculum for tomatoes or (by extrapolation) to potatoes. We further provided evidence that there are R-genes (race-specific resistance genes) in petunias. We further identified that Systemic Acquired Resistance had a major effect causing petunias to be resistant to P. infestans. A second project in which we made significant progress in 2005 was the successful revision of a computer simulation model of the late blight disease that accommodated the greater aggressiveness of exotic
strains of P. infestans that have been distributed around the world. These introduced strains are more aggressive than the previously predominant strains. The simulation model was revised by: 1) empirically determining the dynamics of infection caused by the new strains and including this information into the model; 2) evaluating the model in several locations; and 3) evaluating model performance in regions, which had not been used to generate data for model construction. The model performed very well under all circumstances and is now available for accurate use in forecasting. We evaluated a variety of phonsphonates for pre-harvest application to potatoes to help prevent tuber infections. Foliar applications had a suppressive effect on foliar infection, but only marginal effect on tuber infections. In contrast, drench applications had a very large protective effect. There is probably an important role for phosphonates in an integrated management program for potatoes. Of all the
available fungicides and biopesticides, the phosphonates seem to have the most promise. If realized, the use of phosphonates could relieve much pressure for other fungicide applications. (Protectant fungicides are used in a prophylactic manner under the assumption that if there is no late blight in the foliage, there will be none in the tubers. However, this practice stimulates a large amount of fungicide to be applied.) We also evaluated a mapping population of tetraploid potatoes in collaboration with Walter de Jong, the generator of the population. We located a QTL for resistance in tubers that had a large effect. This QTL is potentially important because of its large effect. If a potato cultivar has resistant tubers, less fungicide will be necessary to suppress disease in the tubers, and this reduced pressure reduce the amount of fungicide used.
Impacts
Our discovery this past year, that pre-harvest drench applications of certain phosphonates can suppress tuber blight when foliage of the potatoes is infected, is potentially a very important discovery. Large amounts of fungicide are applied to foliage under the assumption that if there is no late blight in foliage, there will also not be any in the tubers. Unfortunately, it is very difficult to assure that there is no blight in the foliage, and in some years it is impossible to achieve that situation. If drench applications of phosphonates can protect tubers from late blight, then the need to apply very large amounts of other fungicides to the foliage will be significantly lessened. Two important benefits will result: 1) less fungicide will be released to the environment; and 2) losses due to tuber blight will be lessened. In order to evaluate this potential benefit in production agriculture, additional experiments need to be done. The realization that petunias and
calibrachoas can be sources of inoculum for the tomato and potato late blight pathogen, adds an additional management option to the suppression of tomato and potato late blight in areas where all these crops are grown in proximity such as in parts of Florida during the winter production season. We plan to investigate petunias and calibrachoas as sources of the pathogen under production conditions. If these crops are sources, mitigation techniques applied to these crops will lessen the need for fungicide on potatoes and tomatoes.
Publications
- Andrade-Piedra, J., Hijmans, R. J., Forbes, G. A., Fry, W. E. and Nelson, R. J. 2005. Simulation of potato late blight in the Andes: I, Modification and parameterization of the LATEBLIGHT model. Phytopathology 95: 1191-1199.
- Andrade-Piedra, J., Hijmans, R. J., Juarez, H. S., Forbes, G. A., Shtienberg, D. and Fry, W. E. 2005. Simulation of potato late blight in the Andes: II. Validation of the LATEBLIGHT model. Phytopathology 95: 1200-1208.
- Andrade-Piedra, J. L., Forbes, G. A., Shtienberg, D., Grunwald, N. J., Chacon, M. G., Taipe, M. V., Hijmans, R. J. and Fry, W. E. 2005. Qualification of a plant disease simulation model: performance of the LATEBLIGHT model across a broad range of environments. Phytopathology 95: 1412-1422.
- Becktell, M. C., Daughtrey, M. L. and Fry, W. E. 2005. Epidemiology and management of petunia and tomato late blight in the greenhouse. Plant Disease 89: 1000-1008.
- Becktell, M. C., Daughtrey, M. L. and Fry, W. E. 2005. Temperature and leaf wetness requirements for pathogen establishment, incubation period and sporulation of Phytophthora infestans on Petunia x hybrida. Plant Disease 89: 975-979.
- Forbes, G. A., Chacon, M. G., Kirk, H. G., Huarte, M. A., Van Damme, M., Distel, S., Mackay, G., Stewart, H. E., Lowe, R., Duncan, J. M., Mayton, H., Fry, W. E., Andrivon, D., Ellisseche, D., Pelle, R., Platt, H. W., MacKenzie, G., Tarn, T. R., Colon, L. T., Budding, D. J., Lozoya-Saldana, H., Hernandez-Vilchis, A. and Capezio, S. 2005. Stability of resistance to Phytophthora infestans in potato: an international evaluation. Plant Pathology 54: 364-372.
- Restrepo, S., Myers, K. L., del Pozo, O., Martin, G. B., Hart , A. L., Buell, C. R., Fry, W. E. and Smart, C. D. 2005. Gene Profiling of a Compatible Interaction Between Phytophthora infestans and Solanum tuberosum Suggests a Role for Carbonic Anhydrase. Molecular Plant Microbe Interactions 18: 913-922.
- Zhang, D., Wells, M. T., Smart, C. D. and Fry, W. E. 2005. Bayesian normalization and identification for differential gene expression data. Journal of Computational Biology 12: 391-406.
|
Progress 01/01/04 to 12/31/04
Outputs
Forecasting when a fungicide should be applied versus when it should not be applied to suppress a plant disease is an important component of a strategy to reducing fungicide use. We use the late blight disease because this disease accounts for the most fungicide applied to potato or tomato. Our efforts require an accurate computer simulator of this disease. The first task was to improve the computer simulator, LATEBLIGHT, by providing realistic values and algorithms for functions that were previously only estimated. The modifications included improved equations for the effect of temperature on lesion growth rate and sporulation rate, the incorporation of a temperature dependent latent period, and the use of experimentally determined values for lesion growth rate, sporulation rate and latent period. The revised model was validated by comparing it to epidemics of late blight in diverse locations. We evaluated breeding lines and mapping populations of potatoes for
resistance to late blight in field tests. Materials from the USDA ARS program in Beltsville were uniformly highly resistant. A mapping population from the Cornell breeding population revealed a QTL for resistance on chromosome V that accounted for a high degree of the resistance segregating in the population. We evaluated the effects of diverse biopesticides and biocontrol products for efficacy in suppressing late blight of potato and tomato. Most products had little to no effect on potato or tomato late blight. Materials that were ineffective were Serenade, Root Shield, Plant Shield, However, one inducer (Actigard) of Systemic Acquired Resistance (SAR) had a suppressive effect on late blight on tomatoes. This inducer of SAR had previously had no detectable effect on late blight of potato. We will next investigate the reason for host specificity in efficacy. Biophos, a bio-rational pesticide was partially successful in suppressing late blight on potato foliage in field tests. However,
it did not suppress late blight in potato tubers.
Impacts
Suppression of late blight of potato and tomato is now heavily dependent on traditional fungicides. The disease is a very serious problem because under environmental conditions favorable to the pathogen, the disease can completely destroy a crop. Therefore, growers of both potatoes and tomatoes apply much fungicide. Because it is very difficult to protect plants once the pathogen is established, growers use large amounts of fungicide. Tactics that reduce the amount of traditional fungicide used to protect potatoes and tomatoes from late blight will be welcomed by growers. Alternative disease suppressing tactics will be adopted by growers because of economic and environmental pressures. We have identified that one plant resistance inducer has efficacy to suppress late blight when used on tomatoes. (It has no effect when used on potatoes.) We expect this compound to be adopted in integrated management of tomatoes. It will probably be used early in the season, before
disease pressure increases. In the longer term, plants resistant to late blight must have a role in an integrated strategy. We have identified some Quantitative Trait Loci for late blight resistance, that are sufficiently large to warrant inclusion in a breeding program. These genes are now available in breeding lines for use in breeding programs.
Publications
- Mayton, H.,Simko,I., Rauscher, G., Esposito, B., and Fry, W.E. 2004. A major R-gene from Solanum berthaultii confers qualitative and quantitative resistance to late blight in potato tubers. Phytopathology 94: S68.
|
|