Composition and toxigenic potential of the Fusarium graminearum species complex from maize ears, stalks and stubble in Brazil

Abstract

A large collection (n = 539) of Fusarium graminearum species complex (FGSC) isolates was obtained from Brazilian maize, and collections formed according to geography and maize part: (i) kernel (n = 110) from south and south-central Brazil; (ii) stalk (n = 134) from Paran a state (south); and (iii) stubble (n = 295) from Rio Grande do Sul state (south). Species composition, identified using a multilocus genotype approach, was assessed separately in each collection due to differences in geographic sampling. Overall, three species were found: F. meridionale (Fmer; 67% prevalence) with the nivalenol (NIV) genotype, F. graminearum (Fgra; 19%) with the 15-acetyl (A) deoxynivalenol (DON) genotype, and F. cortaderiae (Fcor; 14%) with the NIV (49/74) or the 3-ADON (25/74) genotype. In kernels, Fmer was spread across all locations and Fgra and Fcor were found mostly at high elevation (>800 m a.s.l.). The majority (97Á8%) of stalk isolates was assigned to Fmer; three were assigned to Fgra. In the stubble, Fmer was less dominant (53%), with a shift towards Fcor as the most frequent species at high elevation sites (>600 m a.s.l.). No differences in the mycelial growth rate were observed among isolates from each species grown at 15°C. Fgra grew faster at 25°C and Fmer showed the widest range of variation across the isolates at both temperatures. The survey data suggest that Fmer may outcompete other species on ears and stalks in comparison to stubble. Additional sampling that controls for other factors, as well as direct testing of aggressiveness on ears and stalk tissue, will be needed to fully evaluate this hypothesis.

Fitness traits of deoxynivalenol and nivalenol-producing Fusarium graminearum species complex strains from wheat

“…Previously, we found that perithecium-borne F. meridionale was highly prevalent in maize stubbles over the surface of two out of three wheat fields, and F. graminearum absent or at very low frequency in stubbles of all three fields (Del Ponte et al, 2015). We then hypothesized that the former was more fit towards maize, which was further confirmed more recently, as F. meridionale was largely dominant on stubbles, stalks and kernels of maize from Brazil (Kühnem et al 2016). In the wheat study, although F. meridionale was dominant in perithecia from maize stubbles on the surface of wheat fields, it was the least frequent in wheat kernels from the same field, which were largely infected by F. graminearum (Del Ponte et al 2015).…”

Common resistance to Fusarium head blight in Brazilian wheat cultivars

“…Based on our results, the selection of superior wheat genotypes could thus be performed using a single aggressive isolate from either species, preferably the most aggressive one, or F. graminearum of the 15-ADON genotype, which has been shown to be highly adaptable as a wheat pathogen Nicolli et al, 2015). In contrast, F. meridionale has been suggested as being more adapted to infecting maize, given the higher frequency in this crop than F. graminearum (Kuhnem et al, 2016).…”

Diversity and pathogenicity of Fusarium graminearum species complex from maize stalk and ear rot strains in northeast China

“…For example, F. graminearum is an important pathogen that can cause stalk rot and ear rot of maize seedlings (Broders et al, 2007), and is the causal agent of stalk, ear and root rots on maize (McMullen et al, 2012). In Brazil, F. meridionale is the dominant species from maize ear and stalks (Kuhnem et al, 2016).…”