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United States Department of Agriculture

Agricultural Research Service

Research Project: COMPARATIVE GENOMIC SYSTEMS FOR MOLECULAR DETECTION AND CONTROL OF TOXIGENIC FUSARIUM

Location: Bacterial Foodborne Pathogens & Mycology Research Unit

Title: Composition of the Fusarium graminearum species complex populations in wheat cropping environments in Southern Brazil

Authors
item Del Ponte, Emerson -
item Ward, Todd
item Spolti, Pierri -
item Gomes, Larissa -
item Nicolli, Camila -
item Kuhnem, Paulo -
item Silva, Cleiltan -
item Tessman, Dauri -

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: October 25, 2013
Publication Date: N/A

Technical Abstract: The Fusarium graminearum species complex (FGSC) comprises several toxigenic species that cause Fusarium head blight (FHB) in wheat. In this study, high number (n=671 isolates) of pathogenic isolates (isolated from infected spikes) was obtained from a 3-year large-scale survey (2009-2011) conducted on wheat fields in PR (n=216) and RS (n=455) states. For the fields of the latter, FHB incidence, latitude and longitude, elevation (m), grain developmental stage at sampling and previous summer crop (corn or soybean), based on visible stubble, were recorded. In 2011, three wheat fields in northern RS, 174 to 275 km apart, were monitored and isolates were obtained from a) stubbles, b) air above canopy during flowering and c) mature spikes. All isolates were identified to species/trichothecene genotype through a multilocus genotyping (MLGT) assay or sequences of the TEF1-alpha gene combined with multiplex PCR. Five species were found in the regional survey: Fgra (557/671), Fmer (86/671), F. cortaderiae (Fcor, 17/671), F. austroamericanum (Faus, n=6/671), F. asiaticum (Fasi, 3/671). All Fgra were of 15-ADON and all Fmer (excepting one of the 15-ADON) and Fasi were of the NIV genotype. Both Fcor and Faus were of NIV or the 3-ADON genotype. For all isolates, frequencies of the 15-ADON, compared to grouping 3-ADON and NIV genotypes, differed significantly (based on a chi-square test) between states. For isolates from RS, the genotype frequencies were influenced by epidemic level (30% incidence threshold) and grain stage during sampling, and not by elevation (< or >600m), or previous crop (corn or soybean). Among the 189 isolates recovered from the three monitored fields, only Fasi was not found, of those found in the regional survey. Fmer was dominant (37/54) in the stubble population, followed by Fcor (16/54) and Fgra (1/54). Fgra was dominant (23/34) in the airborne population, followed by Fmer (6/34) and Fcor (5/34). Fgra was dominant (85/101) in the spike population, followed by Fcor (10/101), Fmer (5/101) and Faus (1/101). The trichothecene genotype-species correspondence was the same as that of the regional survey. Several toxigenic species co-occur and cause head blight of wheat with their relative frequencies varying across geographic regions, which lead to food and feed safety concerns regarding increased prevalence of NIV at some regions. The uncoupling of the dominant populations from stubbles and spikes suggests host/niche adaptation of these populations.

Last Modified: 4/23/2014
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