<p>Frogeye leaf spot (FLS) is a foliar
disease in soybean (<i>Glycine max</i> (L.) Merr.) caused by the fungal
pathogen <i>Cercospora sojina</i> Hara. FLS is commonly found in hot and humid
regions of the southern United States but has become more common in the North
Central states. Foliar application of quinone outside inhibitor (QoI) fungicides
has been one of the major tools used in the management of this disease, but
QoI-resistant <i>C. sojina</i> isolates have been already confirmed in 21
states, including Indiana. We hypothesized that resistant populations of <i>C.
sojina</i> to QoIs fungicides are widespread in Indiana and that sexual
reproduction is occurring within <i>C. sojina</i> populations, likely contributing
to the dissemination of fungicide resistance. The main objectives of this
research were to determine
the distribution of QoI-resistant <i>C. sojina</i> isolates on soybean from
Indiana and to evaluate <i>C. sojina </i>populations for potential sexual reproduction. In the summer of 2019 and 2020,
406 isolates of <i>C. sojina </i>were collected from 32 counties across Indiana
and screened for QoI-fungicide resistance using a PCR-RFLP method. An i<i>n
vitro </i>fungicide sensitivity test was performed on a subset of isolates to
evaluate the sensitivity of <i>C. sojina</i> isolates to azoxystrobin,
pyraclostrobin, picoxystrobin, and prothioconazole. A discriminatory dose of
picoxystrobin (QoI) and prothioconazole (demethylation inhibitor- DMI) were
established at 1 μg/ml and 10 μg/ml, respectively, to distinguish between
QoI-resistant and sensitive isolates and to identify a reduction in sensitivity
to DMI fungicides, respectively. Discriminatory doses were estimated by testing
five concentrations (0.001, 0.01, 0.1, 1, and 10 µg/ml) of each fungicide.
QoI-resistant isolates were found in 29 out of the 32 counties. Two hundred and
fifty-one (251) out of the 406 isolates (61.8%) were confirmed as
QoI-resistant. Partial nucleotide sequences of the cyt <i>b</i> gene from four
resistant and four sensitive <i>C. sojina</i> isolates corroborated the
presence and absence of the G143A mutation, respectively. Results from the sensitivity
assays with azoxystrobin and pyraclostrobin discriminatory doses supported the findings
from the PCR-RFLP assay as all QoI-resistant mutants were inhibited less than
50% when exposed to these doses. Results from this study indicated that
QoI-resistant <i>C. sojina</i> isolates are spread throughout Indiana and that prothioconazole
(DMI) could be a potential supplemental or alternative fungicide to control FLS.
Additionally, mating type distribution was determined in 43 <i>C. sojina</i>
populations for assessment of potential sexual reproduction. Fifteen (15)
populations did not deviate significantly from the expected 1:1 ratio, suggesting
potential for cryptic sexual reproduction in these populations, but further
research on genetic diversity is required to verify these results. </p>
<p> </p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/15057861 |
| Date | 27 July 2021 |
| Creators | Natalia Pineros Guerrero (11186802) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/QUINONE_OUTSIDE_INHIBITOR_QOI_FUNGICIDE_RESISTANCE_AND_MATING-TYPE_DISTRIBUTION_OF_CERCOSPORA_SOJINA_POPULATIONS_ON_SOYBEAN_FROM_INDIANA/15057861 |
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