Browsing by Author "Testen, Anna L."
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- Atahualpa’s Revenge: The Spread of Quinoa Downy MildewTesten, Anna L.; Backman, Paul A. (Northeastern Division of the American Phytopathological Society, 2011)The Andean crop quinoa, Chenopodium quinoa, has gained popularity in recent years due to its nutritious seed and desirable agricultural traits, such as its tolerance to drought and high saline soils. Prized by the Inca, quinoa is now highly desirable to health conscious consumers in North America and Europe. Quinoa also has interesting applications to plant pathology, including being a “universal” virus host as well as its production of antimicrobial compounds. Quinoa is affected by quinoa downy mildew, caused by Peronospora variabilis (formerly P. farinosa f. sp. chenopodii) which attacks quinoa throughout its native range. Quinoa downy mildew is capable of severely reducing yield and is the most devastating disease of this crop. Quinoa downy mildew has been reported in Denmark, Canada and India, despite the diverse growing conditions found in these countries. Most recently, quinoa downy mildew was reported in the United States when it was discovered in two Pennsylvania quinoa trials in 2011. Disease was first limited to 5-10 plants in areas within the plantings, but the cool, rainy conditions present during the 2011 field season quickly led to an epidemic of quinoa downy mildew in Pennsylvania. Koch’s postulates were verified with the pathogen and its identity confirmed with molecular and morphological techniques. P. variabilis is seedborne, with oospores present under the pericarp, but it is also capable of infecting other Chenopodium species including Chenopodium album. However, downy mildew was not observed on any nearby Chenopodium species while conditions were conducive to the disease on quinoa.
- Detection and expression of enterotoxin genes in endophytic strains of Bacillus cereusMelnick, Rachel L.; Testen, Anna L.; Poleatewich, A. M.; Backman, Paul A.; Bailey, B. A. (Society for Applied Microbiology, 2012-03-06)The aim of this study was to determine whether endophytic Bacillus cereus isolates from agronomic crops possessed genes for the nonhaemolytic enterotoxin (Nhe) and haemolysin BL (HBL) and, therefore, have the potential to cause diarrheal illness in humans.
- First Report of Ascochyta Leaf Spot of Quinoa Caused by Ascochyta sp. in the United StatesTesten, Anna L.; McKemy, J. M.; Backman, Paul A. (2013)This report describes infection of Qunioa in Pennsylvania with the Ascochyta Leaf Spot.
- First report of quinoa downy mildew caused by Peronospora variabilis in the United StatesTesten, Anna L.; McKemy, J. M.; Backman, Paul A. (The American Phytopathological Society, 2012)First report of finding quinoa downy mildew in the United States. The disease affects quinoa grown in Andean Region.
- Microbial approaches to support Andean quinoa productionTesten, Anna L. (2012)As Quinoa production increases in response to growing global demand for the crop, it is necessary to develop improved production practices that will support sustainable production. To that end, this thesis examines the ability of the Bacillus species of bacteria to colonize quinoa and to promote quinoa growth, and seeks to identify source of inoculum for Peronospora variabilis, the cause of the quinoa downy mildow disease. Bacillus populations isolated from Pennsylvanian Chenopodium album, Ecuadorean C. quinoa, and Bolivian C. quinoa were screened for the ability to solubilize tricalcium phosphate and this phenotype was paired with 16S sequence data to determine if there were species based patterns of tricalcium phosphate solubilization. Seed-based detection methods using sequencing and PCR with specific primers were developed to detect seedborne oospores of P. variabilis. It was found that seedborne oospores likely play a significant role in the spread of quinoa downy mildew, making the development of management methods for these seedborne oospores critical. Combining these research themes, the potential for Bacillus to reduce the severity of quinoa downy mildew was tested.
- Molecular detection of Peronospora variabilis in quinoa seeds and phylogeny of the quinoa downy mildew pathogen in South America and the United StatesTesten, Anna L.; Jimenez-Gasco, M.; Ochoa, J. B.; Backman, Paul A. (2014)As Quinoa production increases in response to growing global demand for the crop, it is necessary to develop improved production practices that will support sustainable production. To that end, this paper examines the ability of the Bacillus species of bacteria to colonize quinoa and to promote quinoa growth, and seeks to identify source of inoculum for Peronospora variabilis, the cause of the quinoa downy mildow disease. Bacillus populations isolated from Pennsylvanian Chenopodium album, Ecuadorean C. quinoa, and Bolivian C. quinoa were screened for the ability to solubilize tricalcium phosphate and this phenotype was paired with 16S sequence data to determine if there were species based patterns of tricalcium phosphate solubilization. Seed-based detection methods using sequencing and PCR with specific primers were developed to detect seedborne oospores of P. variabilis. It was found that seedborne oospores likely play a significant role in the spread of quinoa downy mildew, making the development of management methods for these seedborne oospores critical. Combining these research themes, the potential for Bacillus to reduce the severity of quinoa downy mildew was tested.
- Plant growth promoting characteristics of Bacillus species associated with Chenopodium quinoaTesten, Anna L.; Backman, Paul A. (2013)As demand for organic quinoa increases and production expands, organic methods, such as the use of plant growth promoting bacteria, are needed to sustain quinoa production. To better understand the potential of Bacillus species to promote growth and reduce disease in quinoa (Chenopodium quinoa), a survey of three Bacillus populations from Bolivian, Ecuadorean and domestic Chenopodium spp. was performed. Four Bacillus species groups common to all populations were tested, including the B. subtilis, B. megaterium, B. simplex, and B. cereus species groups. Nearly 500 isolates were assayed for tricalcium phosphate solubilization, phytase production, IAA production, chitinase production and fungal antagonism. Patterns of specific plant growth promoting phenotypes were observed in different Bacillus species groups across all populations. For example, the tricalcium phosphate phenotype was universal in the B. subtilis and B. megaterium species groups, whereas IAA production was only observed in the B. simplex and B. megaterium species groups. Chitinase production was observed in the B. cereus species group and rarely in other species groups, whereas phytase production was common to all species groups. Isolates with potential for improving quinoa sustainability were identified in this study and isolates with multiple characteristics or consortia of single character Bacilli will be examined in greenhouse and field studies.