Progress 10/01/01 to 09/30/06
Outputs
The plant pathogen, Peronospora tabacina, is the causal agent of tobacco blue mold disease and is the focus of this research project. The natural host range and the production of oospores by this pathogen were investigated. Results to date support the conclusion that eggplants, peppers and tomatoes grown in the US are not hosts of this pathogen. Samples of blue mold diseased tobacco leaf tissues were examined for oospores of the pathogen. Samples from burley and flue-cured leaves from the 2001-2005 production years were examined. No oospores were found in any sample. These observations confirm previous observations that the blue mold pathogen currently does not form oospores during blue mold development in US produced tobacco.
Impacts
US grown eggplants, peppers, tomatoes and tobacco produced in the US are safe to export to countries which do not have blue mold caused by Peronospora tabacina on their solanaceous crops.
Publications
- No publications reported this period
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Progress 10/01/04 to 09/30/05
Outputs
The plant pathogen, Peronospora tabacina, is the causal agent of tobacco blue mold disease and is the focus of this research project. The natural host range and the production of oospores by this pathogen were investigated. Results to date support the conclusion that eggplants, peppers and tomatoes grown in the US are not hosts of this pathogen. Samples of blue mold diseased tobacco leaf tissues were examined for oospores of the pathogen. Samples from burley and flue-cuerd leaves from the 2001-2005 production years were examined. No oospores were found in any sample.These observations confirm previous observations that the blue mold pathogen currently does not form oospores during blue mold development in US produced tobacco.
Impacts
US grown eggplants, peppers, tomatoes and tobacco produced in the US are safe to exprt to countries which do not have blue mold caused by Peronospora tabacina on their solanaceous crops.
Publications
- No publications reported this period
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Progress 10/01/03 to 09/30/04
Outputs
Research focused on the plant pathogen, Peronospora tabacina, the causal agent of the tobaco blue mold disease. The natural host range and the production by this pathogen of oospores within host tissue were studied. No evidence was found to extend the host range to eggplant and pepper fruit. Samples of tobacco were examined from 2001-2004 from burley and flue-cured production areas in the US. No oospores were found in the blue mold diseased tissues in any of these samples. These observations confirm previous observations that blue mold oospores are not currently formed in conjunction with blue mold development in US produced tobacco.
Impacts
US grown tomatoes, eggplant and pepper fruit and US produced tobacco are safe to export to countries which do not have blue mold caused by Peronopora tabacina on their solanaceous crops.
Publications
- No publications reported this period
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Progress 10/01/02 to 09/30/03
Outputs
Research on the pathogen, Peronospora tabacina, which causes blue mold disease of tobacco, have focused on: 1) the natural host range outside of tobacco and 2) the survival and infectivity of pathogen produced sporangiospores and oospores. No evidence was found to extend the host range to eggplant and pepper fruit. Laboratory studies of sporangiospores confirmed previous observations that these spores die within a week of their formation if they do not move to a new tobacco leaf. Samples of tobacco leaves were examined for three years (2001-2003). These samples were from flue-cured and burley production areas. No oospores were observed in any of these samples.These observations confirm previous observations that blue mold oospores are not currently formed in conjunction with blue mold development in US produced tobacco.
Impacts
US grown tomatoes, eggplant and pepper fruit and US produced tobacco are safe to export to countries which do not have blue mold caused by Peronopora tabacina on their solanaceous crops.
Publications
- No publications reported this period
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Progress 10/01/01 to 09/30/02
Outputs
Recent research was on the pathogen, Peronospora tabacina, which causes the blue mold disease of tobacco. Investigations have centered on the natural host range outside of tobacco and on the survival and infectivity of pathogen structures, sporangiospores and oospores. Only commercially grown tobacco and certain Nicotiana spp. Were infected in the US. No evidence was found that would extend the host range to other solanaceous hosts such as tomato, pepper and eggplant. No evidence was found that P. tabacina sporangiospores survive on harvested and cured tobacco leaves that had symptoms of blue mold disease in the field.
Impacts
This research supports the fact that US grown tobacco, tomatoes, peppers and eggplants are safe to export to countries which do not have blue mold disease on their solanaceous crops.
Publications
- No publications reported this period
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Progress 10/01/00 to 09/30/01
Outputs
Research data on the pathogen, Peronospora tabacina, which causes blue mold disease on tobacco, was submitted to USDA-APHIS-PPQ. The data provided information which documented that tobacco produced in the USA and exported to China(PRC) would not contain live sporangiospores and would not contain oospores of P. tabacina. Specific tests demonstrated that commercial tobacco produced in the USA which had been infected with P. tabacina and was harvested, cured and processed for sale, including being redried, did not transmit blue mold. This information was the basis for a "Phytosanitary Protocol for Exporting Tobacco Leaves from the US to the PRC" and was passed into Chinese law on March 19, 2001.
Impacts
This research has made it possible to export US tobacco to China. This will help US tobacco producers and the US trade balance by more than 100 million dollars per year after trade becomes established.
Publications
- No publications reported this period
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Progress 10/01/99 to 09/30/00
Outputs
Since 1979, limited epidemics of tobacco blue mold, caused by Peronospora tabacina, have occurred every year in the USA. Although there is no evidence that the disease can be introduced into countries which do not have blue mold on tobacco purchased for manufacturing, the issue stopped the export of tobacco to certain countries. Our research has demonstrated that: blue mold sporangiospores formed on infected tobacco die in seven days, oospores did not form in recent years, and tobacco redried and prepared for shipping is not infectious. No evidence was found that blue mold could be transmitted with burley or flue-cured tobacco produced in the USA and prepared for export.
Impacts
These results support the position that tobacco produced in the USA is safe to export to foreign countries. This research provides scientific data to support this position and should open export markets to tobacco produced in the USA.
Publications
- No publications reported this period
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Progress 10/01/98 to 09/30/99
Outputs
Recent research was on the pathogen, Peronospora tabacina, which causes the blue mold disease on tobacco. Investigations have centered on the host range outside of tobacco and the survival and infectivity of pathogen structures in cured tobacco leaves harvested for commercial manufacturing processes. Only commercial tobacco and certain Nicotiana spp. were infected with this pathogen in the US. No evidence was found that would extend the host range to solanaceous hosts such as tomato, pepper or eggplant grown in the field in the US. No evidence was found that P. tabacina sporangiospores survive on harvested and cured commercial tobacco leaves that had symptoms of blue mold disease in the field.
Impacts
This research supports the fact that US grown tobacco, tomatoes, peppers and eggplants are safe to export to countries which do not currently have blue mold disease.
Publications
- No publications reported this period
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Progress 01/01/98 to 12/31/98
Outputs
Nonpathogenic binucleate Rhizoctonia fungi (BNR) controlled black shank caused by Phytophthora parasitica var. nicotianae on greenhouse-grown tobacco seedlings in styrofoam float trays. Three BNR isolates were incorporated into a soil-less mix on colonized, pulverized, sifted rice particles; colonized whole rice grains; or on pelleted tobacco seeds coated with 0.5% methyl cellulose. Five-wk-old seedlings were inoculated with zoospores of P. parasitica var. nicotianae and disease rated over 10d. The level of protection varied with method of BNR application, ranging from 40-70%. Overall, control was better when BNR isolates were applied on rice inocula rather than on BNR-colonized tobacco seeds. From 15% to 80% of individual roots from seedlings grown in soil-less mix amended with BNR-colonized rice grains were colonized while only 0-20% of roots from seedlings grown from BNR-colonized tobacco seeds were colonized. Likewise, 37-100% of soil-less mix amended with
BNR-colonized rice grains contained BNR's while less than 3% of soil-less mix was colonized when seedlings emerged from BNR-colonized tobacco seeds. This is the first demonstration of biocontrol of Phytophthora by BNR fungi.
Impacts
(N/A)
Publications
- CARTWRIGHT, D.K., SPURR, H.W. 1998. Biological control of Phytophthora parasitica var. nicotianae on tobacco seedlings with non-parasitic binuclate Rhizoctonia fungi. Soil Biol. Biochem. 30:1879-1884.
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Progress 01/01/97 to 12/31/97
Outputs
A practical and rapid technique for screening tobacco cultivars for resistance to black shank was developed using a greenhouse float system. In this system, tobacco seedlings grown in clay pots and transplanted to styrofoam trays were inoculated with 5,000 zoospores of Phytophthora parasitica var. nicotianae per seedling. Based on previous reports of field resistance, two cultivars each of highly resistant, moderately resistant, and susceptible cultivars were screened in this system. In three experiments, the highly resistant and highly susceptible cultivars were easily separated based on disease incidence, correlating closely with published disease indices determined in the field. The moderately resistant cultivars were more difficult to separate based on reaction. This system has potential to provide a quick and convenient method for evaluating tobacco cultivars for resistance to black shank. A modification of the system is being used for evaluating the efficacy of
microbial agents for control of black shank.
Impacts
(N/A)
Publications
- CARTWRIGHT, D.K., SPURR, H.W.JR, and SISSON, V.A. 1996. Greenhouse floatsystem evaluation of tobacco cultivars for resistance to black shank. Tobacco Science 39:117-120.
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Progress 01/01/96 to 12/30/96
Outputs
A practical and rapid technique for screening tobacco cultivars for resistance to black shank was developed using a greenhouse float system. In this system, tobacco seedlings grown in clay pots and transplanted to styrofoam trays were inoculated with 5,000 zoospores of Phytophthora parasitica var. nicotianae per seedling. Based on previous reports of field resistance, two cultivars each of highly resistant, moderately resistant, and susceptible cultivars were screened in this system. In three experiments, the highly resistant and highly susceptible cultivars were easily separated based on disease incidence, correlating closely with published disease indices determined in the field. The moderately resistant cultivars were more difficult to separate based on reaction. This system has potential to provide a quick and convenient method for evaluating tobacco cultivars for resistance to black shank. A modification of the system is being used for evaluating the efficacy of
microbial agents for control of black shank.
Impacts
(N/A)
Publications
- CARTWRIGHT, D.K., SPURR, H.W. JR, and SISSON, V.A. 1996. Greenhouse floatsystem evaluation of tobacco cultivars for resistance to black shank. Tobacco Science 39:117-120.
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Progress 01/01/95 to 12/30/95
Outputs
Studies of spore viability over time (longevity) have used Peronospora sporangiospores produced on laboratory tobacco plants. We tested longevity of sporangiospores produced on tobacco leaves during blue mold field epidemics. Viability of sporangiospores was determined as being percentage germination after making blots in the field on 1.5% water agar followed by incubation at 20 C for 24 hr. Sporangiospores survived about three days following production. When secondary lesions appeared 10-14 days later, sporangiospores in primary lesions were dead. Large numbers of dead sporangiospores remained on leaf lesions through harvest. Oospores observed in leaf lesions in 1995 were thin-walled and hyaline, similar to oospores found in the 1979 epidemic. The viability of these oospores in not known. Thick- walled, red-brown oospores were previously ascribed to P. tabacina. This confirms that two species of Peronospora infest tobacco and cause a downy mildew known as blue
mold.
Impacts
(N/A)
Publications
- CARTWRIGHT, D.K., SPURR, H.W., JR., and SHEW, H.D. 1995. Commercial potting medium as a source of Pythium causing a disease on tobacco transplants. Plant Disease 79:538.
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Progress 01/01/94 to 12/30/94
Outputs
Brown spot, blue mold, barn rot and Granville wilt disease of tobacco are the principal focus of this research project. The survival of the blue mold pathogen, Peronospora tabacina, in harvested and cured tobacco was investigated to gain access to Asian markets for U.S. leaf. Burley and flue-cured tobacco leaves with blue mold lesions were obtained from various locations. Infected tissues were examined for sporangiospores and oospores. When found, these spores were tested for viability. No viable spores were found in cured leaf. The host status of tomatoes to tobacco blue mold was investigated to gain access to Japanese markets for U.S. produced tomatoes. Ten selected tomato cultivars were inoculated with P. tabacina sporangiospores in a series of experiments designed to favor infection and disease development. No signs or symptoms of blue mold resulted on tomato foliage or fruit.
Impacts
(N/A)
Publications
- SPURR, H.W., JR. 1994. The microbial ecology of fruit vegetable surfaces. in: Biological Control of Postharvest Diseases. Wilson and Wisniewski eds. CRC Press.
- SPURR, H.W., JR., MAIN, C.E., and REDLIN, S.C. 1994. Survival of blue mold pathogen in harvested tobacco leaves. 38p. in: Information Bulletin, CORESTA Congress.
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Progress 01/01/93 to 12/30/93
Outputs
Brown spot, blue mold, barn rot and Granville wilt diseases of tobacco are the principal focus of this research project. The survival of the blue mold pathogen, Peronospora tabacina, in harvested and cured tobacco is being investigated to help gain access to Asian markets for U.S. leaf. Burley and flue-cured tobacco leaves with blue mold lesions were obtained from various locations. Infected tissues were examined for sporangiospores and oospores. When found, these spores were tested for viability. No viable spores were found to date in cured leaf. The host status of tomatoes to tobacco blue mold is being investigated to gain access to Japanese markets for U.S. produced tomatoes. Sustainable agriculture studies were made with no-till tobacco. In selected plant mulches a lower incidence of Granville wilt disease was observed.
Impacts
(N/A)
Publications
- ELLIOTT, V.J. and SPURR, H.W., JR. 1993. Temporal dynamics of chlorothalonil residues on peanut foliage and the influence of weather factors and plant growth. Plant Disease 77(5):455-460.
- SPURR, H.W., JR. 1993. Overcoming barriers to biological control. pp. 47-49 in: Biological Control: Developing Strategies for the 90's. Proc. NCDA/NCSU Nat'l. Conf. McDonald, R. C., Harper, J. D., and Dickerson, W. A., eds. 79p.
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Progress 01/01/92 to 12/30/92
Outputs
Brown spot, blue mold, barn rot and Granville wilt diseases of tobacco are the principal focus of this research project. Blue mold diseased tobacco leaves continue to be collected from sources around the world to study the morphology of the sexual structures (oospores) of the fungal pathogen Peronospora tabacina. Studies of tobacco leaf microflora are providing information on the dynamic populations associated with healthy tobacco leaves and are the primary source of microorganisms used for development of biological controls. Eleven spp. of endophytic fungi were frequently isolated from tobacco leaves. The two most frequently isolated fungi were Alternaria alternata in 86% of samples and Cladosporium cladosporoides in 37%. Frequency patterns were similar to observations made in 1970. Endophytic A. alternata isolates from healthy tissue were generally non pathogenic when compared to A. alternata isolates from brown spot lesions. C. cladosporoides isolates displayed a
range in variability in culture. A collection of these fungal isolates are being tested as potential biological control agents.
Impacts
(N/A)
Publications
- SPURR, JR., H.W. and MAIN, C.E. 1991. Morphology of Peronospora tabacina reproductive structures. 1991 Proceedings of the CORESTA Agro-Phyto Meeting, Louisville, KY:24. (abstract)
- SPURR, JR., H.W. 1991. Development and control of bacterial barn rot in flue- cured tobacco. 1991 CORESTA Proceedings, Louisville, KY:6. (abstract)
- SPURR, JR., H.W. 1992. Frequency, distribution and variability in isolates of endophytic fungi from tobacco leaves. Phytopathology 82:1078. (abstract)
- THAL, W.M., SAUTER, H.P., SPURR, JR., H.W. and ARROYO, T. 1992. Factors influencing airborne ascospore counts of mycosphaerella fijiensis. Phytopathology 82:1163. (abstract)
- THAL, W.M., SAUTER, H.P., SPURR, JR., H.W. and ARROYO, T. 1992. Patterns in airborne ascospore counts of mycosphaerella fijiensis, cause of black sigatoka on banana. Phytopathology 82:1105. (abstract).
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Progress 01/01/91 to 12/30/91
Outputs
Brown spot, blue mold, barn rot and Granville wilt diseases of tobacco are the principal focus of this research project. Studies of tobacco leaf microflora are providing information on the dynamic populations associated with healthy tobacco leaves and are the primary source of microorganisms used for development of biological controls. Blue mold diseased tobacco leaves continue to be collected from sources around the world to study the morphology of the sexual structures (oospores) of the fungal pathogen Peronospora tabacina. Adhesion assays were used to characterize tobacco leaf surface components that attach P. tabacina sporangia to its host. Attachment on glass and bean leaves was used as a comparison. Tobacco brown spot conidia, Alternaria alternata, were also used. Attachment to the three surfaces by both types of spores began at time of contact. Spore viability was not essential for attachment. Pretreatment with pronase E or trypsin significantly decreased
attachment of P. tabacina sporangia to tobacco leaf surfaces but not of A. alternata conidia. Pronase E treatment of P. tabacina sporangia after attachment to tobacco caused detachment. It was concluded that a protein is a component in the attachment of P. tabacina sporangia to tobacco.
Impacts
(N/A)
Publications
- SPURR, H.W., Jr., ELLIOTT, V.J., and THAL, W.M. 1991. Managing epiphytic microflora for biocontrol. Pp. 3-13. In: Biological Control of Postharvest Diseases of Fruits and Vegetables, Workshop Proceedings. C. L. Wilson and E.
- MENETREZ, M.L. and SPURR, JR., H.W. 1990. Attachment of Peronospora tabacina spores to surfaces. Tobacco Science 34:88- 92.
- ELLIOTT, V.J. and SPURR, JR., H.W. 1990. Characterization of bacterial flora of peanut foliage by computer-aided fatty acid methyl ester analysis. 5th Int. Symp. on the Microbiology of the Phyllosphere. p 35. (Abstract).
- ELLIOTT, V.J. and SPURR, H.W., JR. 1990. Temporal Dynamics of Chlorothalonil Residues on Peanut Foliage. Phytopathology 80:1041. (Abstract).
- SPURR, H.W., JR. 1990. Brown Spot. Pp 10-12. In: Shew, H.D. and Lucas, G.B., eds. Tobacco Compendium. APS Press, St. Paul, MN.
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