Original Article. Geographic distribution of Fusarium culmorum chemotypes associated with wheat crown rot in Iraq

Abstract

Fusarium crown rot (FCR) is an important disease of wheat and other grains that has had a signifi cant impact on cereal crop production worldwide. Fusarium species associated with FCR can also produce powerful trichothecenes mycotoxins that pose a considerable health risk to humans and animals that consume infected grains. In this study we examined Fusarium species of wheat from diff erent regions of Iraq that showed FCR symptoms. Twenty-nine isolates were collected overall, and the marker gene translation elongation factor 1 alpha (TEF-1α) was sequenced in order to determine their taxonomic identities. All isolates were determined to be F. culmorum, and primers targeting tri-cluster genes were used in order to further characterize isolates into specifi c trichothecene chemotype strains. Five of the 29 isolates were determined to be the nivalenol (NIV) chemotype, while the rest of the isolates recovered were the deoxynivalenol (DON) chemotype. All DON--type isolates produced 3Ac-DON, while the 15Ac-DON-type was not detected. Th e majority of the NIV-type isolates originated from wheat growing regions in the mid-latitudes of Iraq, while the DON-type isolates were recovered from areas distributed broadly across the country. To the best of our knowledge, this study is the fi rst to report on the distribution of specifi c F. culmorum chemotypes from FCR diseased wheat in Iraq.

Mating Type Characterization of Fusarium Culmorum Strains Causing Wheat Crown Rot in Iraq

“…Here we further characterize Iraqi strains of F. culmorum, using specific primers to determine mating types of isolates from CR diseased wheat collected across the country. We hypothesized that both MAT-1 and MAT-2 alleles would be detectable within F. culmorum isolates from Iraq and that they would also exhibit distinct biogeographic patterns, similar to those observed previously for F. culmorum CR associated chemotypes (Matny et al, 2016).…”

“…The teleomorphic stage of F. culmorum has never been discovered; however, population studies suggest sexual recombination does occur in the species (Gargouri et al, 2003). In a previous study, we demonstrated the existence of distinct wheat CR associated chemotypes in Iraq, with the DON-type being widespread and the NIV-type restricted to mid-latitudes of the country (Matny et al, 2016). Recent studies have shown a close to 1:1 distribution of F. culmorum idiomorphs across the globe, including various parts of the Middle East (Obanor et al, 2010) and further suggesting sexual recombination.…”

“…Wheat plants exhibiting crown rot symptoms were collected from various locations in north and central Iraq (Figure 1). Fusarium isolates were prepared using methods outlined previously (Matny et al, 2016). Briefly, a 1 cm 2 of diseased tissue was harvested from each plant using a scalpel sterilized with 10% sodium hypochlorite (bleach).…”

“…Extracted DNAs were tested for quality and quantified using a NanoDrop 2000 (Thermo-Fisher Scientific, USA). Amplification of translation elongation factor 1 alpha (TEF-1α) was carried out using the primers EF1 and EF2 (O'Donnell et al, 2000) following the protocol outlined previously (Matny et al, 2016). Primer pairs used in the mating type study (Table 1) included fusALPHAfor and fusALPHArev (amplifying the mating-type alpha-box protein MAT1-1) and fusHMGfor and fusHMGrev (amplifying the high mobility group HMG-box protein MAT1-2).…”

“…Studies suggest F. culmorum is replacing other species, such as F. graminearum, as the primary CR and HB strains in some parts of Europe, and this is likely due to climatic factors (Waalwijk et al, 2003;Jennings et al, 2004;Miedaner et al, 2008). Fusarium culmorum is a common cause of CR in the Middle East (Motallebi et al, 2015), including Iraq where it is widespread and potentially among the more aggressive CR causing strains found there (Matny et al, 2012(Matny et al, , 2016 Fusarium is an asexual fungus (anamorph) in the Ascomycota, with the ascospore producing sexual stage (teleomorph) known in the genera Calonectria, Gibberella, and Nectria (Booth 1981). Ascomycota species can be homothallic (self-fertile) or heterothallic (self-sterile), and mating compatibility in this phylum is controlled by a single mating compatibility locus (MAT) with two dissimilar (idiomorphic) alleles, MAT-1 and MAT-2 (Niessen 2007).…”