Browsing by Autor "Anna L. Testen"

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    Molecular Detection of <i>Peronospora variabilis</i> in Quinoa Seed and Phylogeny of the Quinoa Downy Mildew Pathogen in South America and the United States
    (American Phytopathological Society, 2013) Anna L. Testen; María del Mar Jiménez-Gasco; J. Ochoa; P. A. Backman
    Quinoa (Chenopodium quinoa) is an important export of the Andean region, and its key disease is quinoa downy mildew, caused by Peronospora variabilis. P. variabilis oospores can be seedborne and rapid methods to detect seedborne P. variabilis have not been developed. In this research, a polymerase chain reaction (PCR)-based detection method was developed to detect seedborne P. variabilis and a sequencing-based method was used to validate the PCR-based method. P. variabilis was detected in 31 of 33 quinoa seed lots using the PCR-based method and in 32 of 33 quinoa seed lots using the sequencing-based method. Thirty-one of the quinoa seed lots tested in this study were sold for human consumption, with seed originating from six different countries. Internal transcribed spacer (ITS) and cytochrome c oxidase subunit 2 (COX2) phylogenies were examined to determine whether geographical differences occurred in P. variabilis populations originating from Ecuador, Bolivia, and the United States. No geographical differences were observed in the ITS-derived phylogeny but the COX2 phylogeny indicated that geographical differences existed between U.S. and South American samples. Both ITS and COX2 phylogenies supported the existence of a Peronospora sp., distinct from P. variabilis, that causes systemic-like downy mildew symptoms on quinoa in Ecuador. The results of these studies allow for a better understanding of P. variabilis populations in South America and identified a new causal agent for quinoa downy mildew. The PCR-based seed detection method allows for the development of P. variabilis-free quinoa seed, which may prove important for management of quinoa downy mildew.
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    Plant-Growth-Promoting Traits of <i>Bacillus</i> Species Associated with Quinoa (<i>Chenopodium quinoa</i>) and Lambsquarters (<i>Chenopodium album</i>)
    (2022) Anna L. Testen; Mayra Claros Magnus; P. A. Backman
    As quinoa (Chenopodium quinoa Willd.) production expands globally, methods to mitigate abiotic and biotic production constraints are needed. One potential method to improve quinoa productivity is through the use of plant-growth-promoting microbes. In this study, we examined Chenopodium-associated Bacillus populations from Bolivia, Ecuador, and the United States for their ability to solubilize phosphate, antagonize Fusarium oxysporum, and produce phytase, indole acetic acid (IAA), and chitinase. The majority (99%) of isolates screened (n = 496) exhibited one or more traits related to plant growth promotion. Phosphate solubilization was observed in 75%, phytase production in 89%, IAA production in 44%, chitinase production in 13%, and antagonism to F. oxysporum in 8% of screened isolates. Some species or species groups screened were more likely than others to exhibit certain traits, such as B. megaterium, B. pumilus group, and B. subtilis group for phosphate solubilization and B. cereus group for chitinase production. This study indicates that many Chenopodium-associated Bacillus isolates exhibit plant-growth-promoting traits and could be studied further to promote quinoa production.