Progress 10/01/06 to 12/31/09
Outputs
OUTPUTS: Through this project, we have developed a geranium-Pseudomonas pathosystem for the study of pseudomonas diseases of ornamentals. Inoculation by pin-prick followed by covering of the plant in transparent plastic bag produces the best disease symptoms under experimental conditions. We have also isolated more than fifty microbial isolates from geranium leaf surfaces of potential beneficial uses as biocontrol agents. With the increase in popularity of organic agriculture, these organism hold potential for use as biological control agents against foliar diseases of ornamentals. The epiphytic microbial isolation regime was broadened to include perennial geranium in ornamental gardens. The inclusion of isolates from perennial plants is to allow for the isolation of more permanent leaf surface residents who are more adapted to life on in the leaf surface. About fifty additional microbial isolates were purified from the leaf surfaces of different Geranium species. These isolates make an important resource for screening for biocontrol candidates not only on geranium but other ornamentals as well. The findings of the project were presented as posters and oral presentations by both the PI and the students within the School of Agriculture and the university. In addition, part of the findings has been submitted for publications in the Proceedings of the Southern Nursery Association. Two graduate and one undergraduate students received training within the project. Thus, the project also contributed to the fulfillment of the future agricultural labor force needs of the nation. In addition to their contribution to the project, the students received training in molecular and microbiological techniques involved in plant-pathogen interaction studies. PARTICIPANTS: C. Korsi Dumenyo, Principal Investigator Paul Agyemang, Graduate Student Peter Prestwich; Graduate Student Marie Blacksmith, Undergraduate Student TARGET AUDIENCES: The immediate target audience is the agricultural research community. Practitioners as well as researchers of plant pathology will be able to request isolates of the culture collection for testing against ornamental diseases. Ultimately, the farmer will benefit when this knowledge is used in further research to develop disease management strategies. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Zonal geranium (Pelargonium spp.) cultivars Marveric Pink and Horizon Orange were inoculated in greenhouse with strains of Pseudomonas savastanoi, P. cichorii, P. viridiflava, P. corrugata and P. syriange pathovars syringae, morsprunorum, and tomato. The different inoculation conditions tested were Spraying of inoculum onto leaf surfaces, Spray followed by pin-prick of the leaf sufaces, and Pin prick of the inoculum followed by covering the plant in transparent plastic bags. Inoculation of the plants without covering them with plastic bags did not result in infection and wounding of the leaf surface with the pin-prick was also required for optimum infection as spayed plants that were covered up were not infected. The most severe symptoms were incited by strains of Pseudomonas cichorii but there were also differences among these strains with respect to disease severity. To understand better the nature of the interactions between geranium epiphytes and plant pathogenic Pseudomonas species, we isolated and characterized part of the diversity of bacterial population on the phyllosphere of zonal geranium (Pelargonium spp.) cv. Maverick Pink and Horizon orange and perennial geranium in municipal garden. Leaves were obtained from plants growing in a home garden and the surfaces were imprinted on agar media to isolate the leaf surface microbes. Overall, more than 50 isolates were obtained, purified and stored. Of these, twenty-seven bacterial isolates obtained from Maverick Pink and Horizon Orange were characterized further. The isolates were purified and characterized through Gram staining, potassium hydroxide and hydrogen peroxide tests. Sixteen of the isolates were Gram positive and 11 were Gram negative. For identification to species level, conditions are being optimized for the amplification of 16S rDNA from each of the isolates. Knowledge of the composition of the epiphyte population should allow us to study interactions with pathogens. The bacterial collection has also added to the available potential biocontrol agents that can be screened for activity against a variety of plant disease.
Publications
- Dumenyo, C.K. and Agyemang, P. 2010. Interaction between cultitvars of Periwinkle and plant pathogenic Pseudomonas. Proceedings of Southern Nursery Association. (In Press)
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: Zonal geranium (Pelargonium spp.) cultivars Marveric Pink and Horizon Orange were inoculated in greenhouse with strains of Pseudomonas savastanoi, P. cichorii, P. viridiflava, P. corrugata and P. syriange pathovars syringae, morsprunorum, and tomato. The different inoculation conditions tested were Spraying of inoculum onto leaf surfaces, Spray followed by pin-prick of the leaf sufaces, and Pin prick of the inoculum followed by covering the plant in transparent plastic bags. Inoculation of the plants without covering them with plastic bags did not result in infection and wounding of the leaf surface with the pin-prick was also required for optimum infection as spayed plants that were covered up were not infected. The most severe symptoms were incited by strains of Pseudomonas cichorii but there were also differences among these strains with respect to disease severity. To understand better the nature of the interactions between geranium epiphytes and plant pathogenic Pseudomonas species, a study was began to isolate and characterize the diversity of bacterial population on the phyllosphere of zonal geranium (Pelargonium spp.) cv. Maverick Pink and Horizon orange. Leaves were obtained from plants growing in a home garden and the surfaces were imprinted on agar media to isolate the leaf surface microbes. Sixteen and 11 bacterial isolates were respectively obtained from Maverick Pink and Horizon Orange. The isolates were purified and characterized through Gram staining, potassium hydroxide and hydrogen peroxide tests. Sixteen of the isolates were Gram positive and 11 were Gram negative. For identification to species level, conditions are being optimized for the amplification of 16S rDNA from each of the isolates. Knowledge of the composition of the epiphyte population should allow us to study interactions with pathogens. PARTICIPANTS: Dumenyo, C. Korsi, Principal Investigator Prestwich, Peter; Graduate Student Blacksmith, Marie; Undergraduate Student TARGET AUDIENCES: The immediate target audience is the agricultural research community. Ultimately, the farmer will benefit when this knowledge is used in further research to develop disease management strategies. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The findings from this project have led to the conclusion that strains Pseudomonas cichorii interaction with geranium make a good pathosystem for the study if Pseudomonas diseases of ornamentals. Inoculation of the plants with a pin-prick of leaf surface with bacterial suspension produced the best infection. Probably because of a requirement for high humidity, it is essential to cover the inoculated plants with transparent plastic bags for optimum infection. Subsequent studies will use these findings.
Publications
- Prestwich, P. and Dumenyo, C.K. 2009. Isolation and characterization of epiphytic bacteria population from geranium (Pelargonium spp) cvs. Maverick Pink and Horizon Orange. 31st Annual University-Wide Research Symposium. Tennessee State University, March 30- April 3, 2009
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: An experiment was performed to establish a pathosystem between plant pathogenic Pseudomonas species and an ornamental plant species. Periwinkle, Catharanthus roseus cultivars Titan Blush, Mediterranean Apricot Broad eye, Pacifica Red, and First Kiss Blueberry were inoculated with Pseudomonas syringae pathovar syringae B728a, P. s. tabaci strain 5, P. s. glycenia race 1, P.s. tomato DC3000 and buffer. Inoculation was done by spraying about 50 ml of bacterial suspended in phosphate buffer to (A600 = 0.1) unto five plants of each Periwinkle cultivar with phosphate buffer as control. The plants were observed regularly and scored for disease symptoms and severity after six weeks. Where symptoms developed, the first signs observed were slight yellowing of the leaves which slowly changed to necrosis of the entire leaf. A disease severity scale of zero to five was developed and used to score the symptoms by two independent people. The average score from the two scorers was used in
two-way analysis of variance. The data indicted significant differences among the strains, the cultivars and an interaction between the bacterial strains and periwinkle cultivar. The slightest symptoms were observed with P. s. tabaci on First Kiss Blueberry with an average score of 0.1. These plants were indistinguishable from the buffer-inoculated plants. The most severe symptoms on the other hand were observed on P. s. syringae 728A on First Kiss Blueberry again with an average score of 3.05.
PARTICIPANTS: Dumenyo, C. Korsi, Principal Investigator
TARGET AUDIENCES: The immediate target audience is the agricultural research community. Ultimately, the farmer will benefit when this knowledge is used in further research to develop disease management strategies.
Impacts
Establishment of a pathosystem is the first step in setting up a model system to study how a particular pathogen interacts with the host. The results of this experiment has established that we can use Periwinkle cultivar first Kiss Blueberry as a host of Pseudomonas syringae pv. syringae B728A to study how ornamentals plant species interact with leaf surface microbes. This change in knowledge is going to be applied in the study of Pseudomonas diseases of ornamental crops.
Publications
- No publications reported this period
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Progress 10/01/06 to 12/31/06
Outputs
This project began in October 2006 heading into winter. During the winter, arrangements were made for the required logistics. The experiments will begin with the warm weather in the spring.
Impacts
Since Pseudomonas syringae pathovars infect most crop species cultivated in the country, an understanding of the mechanisms of their pathogenesis will potentially affect the management of the diseases they cause in all these hosts.
Publications
- No publications reported this period
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