Aggressiveness of Fusarium Species and Impact of Root Infection on Growth and Yield of Soybean.

Iowa State University, Plant Pathology and Microbiology, Ames, Iowa, United States
Phytopathology (Impact Factor: 2.75). 03/2013; 103(8). DOI: 10.1094/PHYTO-08-12-0207-R
Source: PubMed

ABSTRACT Fusarium spp. are commonly isolated from soybean roots but the pathogenic activity of most species is poorly documented. Aggressiveness and yield impact of nine species of Fusarium were determined on soybean in greenhouse (50 isolates) and field microplot (19 isolates) experiments. Root rot severity and shoot and root dry weights were compared at growth stages V3 or R1. Root systems were scanned and digital image analysis was conducted; yield was measured in microplots. Disease severity and root morphology impacts varied among and within species. F. graminearum was highly aggressive (root rot severity >90%), followed by F. proliferatum and F. virguliforme. Significant variation in damping-off (20 to 75%) and root rot severity (<20 to >60%) was observed among F. oxysporum isolates. In artificially-infested microplots, root rot severity was low (<25%) and mean yield was not significantly reduced. However, there were significant linear relationships between yield and root symptoms for some isolates. Root morphological characteristics were more consistent indicators of yield loss than root rot severity. This study provides the first characterization of aggressiveness and yield impact of Fusarium root rot species on soybean at different plant stages and introduces root image analysis to assess the impact of root pathogens on soybean.

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Available from: Maria Mercedes Diaz Arias, Feb 06, 2015
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    • "These arguments were based on failed attempts to complete Koch's postulates, following direct inoculations of seedling hypocotyls or applications of spore suspensions of F. graminearum to flowers (Fernandez and Fernandes 1990). At present F. graminearum is recognized as a primary pathogen of soybean in several countries in the American continents (Broders et al. 2007; Diaz Arias et al. 2013; Ellis et al. 2011; Martinelli et al. 2004; Pioli et al. 2004; Xue et al. 2007). Soybean (Glycine max L. Merr.) is the most important field crop in Argentina, where the planted area has reached 11,000,000 ha with annual production approximately 35,000,000 metric tonnes (MAGPyA (http:// "
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    ABSTRACT: Soybean (Glycine max L.) is one of the main crops in Argentina. Most of the studies of pathogenicity in the Fusarium graminearum complex have focused on strains isolated from wheat and maize, and there is little information on strains isolated from soybean. Our objective in the present study was to compare the pathogenicity among soybean isolates of different phylogenetic species within the Fusarium graminearum complex on soybean seedlings under controlled conditions. Six strains representing three different phylogenetic species (F. graminearum, F. meridionale and F. cortaderiae) were identified by partial sequencing of the Translation Elongation Factor -1α gene (TEF-1) and evaluated for pathogenicity. All six strains reduced emergence, mainly by causing pre-emergence damping-off, seedling height and root dry weight and produced abnormal seedlings. The mean disease severity averaged across all isolates was approximately 3.0 in a 0–4 rating scale where 0 = healthy seedling and 4 = dead seedling. Significant differences in pathogenicity were observed among F. graminearum, F. meridionale and F. cortaderiae. These results are consistent with the hypothesis that different phylogenetic species within the Fusarium graminearum complex isolated from soybean are pathogenic under controlled conditions to soybean seedlings in Argentina. The present study demonstrates for the first time the pathogenic effect of F. meridionale on soybean in Argentina.
    European Journal of Plant Pathology 02/2014; 138(2). DOI:10.1007/s10658-013-0332-2 · 1.71 Impact Factor
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    ABSTRACT: Fusarium graminearum is a toxigenic fungal pathogen which causes Fusarium head blight (FHB) and crown rot (CR) on cereal crops worldwide. This fungus also causes damping off and crown and root rots at the early stage of crop development in soybean cultivated in North and South America. Several F. graminearum genes were investigated for their contribution to FHB in cereals but no inherent study is reported for the dicotyledonous soybean host. In this study we determined the disease severity on soybean seedlings of five single gene disrupted mutants of F. graminearum, previously characterized in wheat spike infection. Three of these mutants are impaired on a specific function as the production of deoxynivalenol (DON, ∆tri5), lipase (ΔFgl1) and xylanase (∆xyl03624), while the remaining two are MAP kinase mutants (ΔFgOS-2, ∆gpmk1) which are altered in signaling pathways. The mutants that were reduced in virulence (Δtri5, ΔFgl1 and ΔFgOS-2) or avirulent (Δgpmk1) on wheat, were correspondently less virulent or avirulent in soybean seedlings, as shown by the extension of lesions and seedling lengths. The ∆xyl03624 mutant was as virulent as the WT mirroring the behavior observed in wheat. However, a different ranking of symptom severity occurred in the two hosts: the ΔFgOS-2 mutant, that infects wheat spikelets similarly to Δtri5 and ΔFgl1 mutants, gave much reduced symptoms in soybean. Differently from the other mutants, we observed that the ΔFgOS-2 mutant was several fold more sensitive to the glyceollin phytoalexin suggesting that its reduced virulence may be due to its hypersensitivity to this phytoalexin. In conclusion, lipase and DON seem important for full disease symptoms development in soybean seedlings, OS-2 and Gpmk1 MAP kinases are essential for virulence, and OS-2 is involved in conferring resistance to the soybean phytoalexin.
    Phytopathology 04/2014; 104(11). DOI:10.1094/PHYTO-12-13-0355-R · 2.75 Impact Factor
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    ABSTRACT: Isolates in the Fusarium oxysporum species complex (FOSC) from soybean range from non-pathogenic to aggressive pathogens causing seedling damping-off, wilt, and root rot. The objective of this research was to characterize the genotype and phenotype of isolates within the FOSC recovered predominantly from soybean roots and seedlings. Sequence analyses of the translation elongation factor (tef1α) gene and the mitochondrial small subunit (mtSSU), PCR-RFLP analysis of the intergenic spacer (IGS) region, and identification of the mating type loci were conducted for 170 isolates. Vegetative compatibility (VC) tests were conducted for 114 isolates. Isolate aggressiveness was tested using a rolled towel assay for 159 isolates. Phylogenetic analysis of the tef1α and mtSSU and PCR-RFLP analysis of the IGS region separated the FOSC isolates into five clades, including F. commune. Both mating type loci, MAT1-1 or MAT1-2, were present in isolates from all clades. The VC tests were not informative, as most VC groups consisted of a single isolate. Isolate aggressiveness varied within and among clades; isolates in clade 2 were significantly less aggressive (P <0.0001) when compared to isolates from the other clades and F. commune. The results from this study demonstrate the high levels of genotypic and phenotypic diversity within the FOSC from soybean, but further work is needed to identify characteristics associated with pathogenic capabilities.
    Phytopathology 07/2014; 104(12). DOI:10.1094/PHYTO-02-14-0043-R · 2.75 Impact Factor
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