Chlamydospores of Fusarium roseum 'Graminearum' as Survival Structures

Nyvall, Robert F.

doi:10.1094/phyto-60-1175

Cited by 25 publications

(15 citation statements)

References 2 publications

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“…Conidia are produced from the sporodochia on infected crops and are responsible for secondary infection [6]. Moreover, modified conidia (chlamydospores or chlamydospore-like structures) are proposed to be other survival structures [1], [7], [8].…”

Section: Introductionmentioning

confidence: 99%

AbaA Regulates Conidiogenesis in the Ascomycete Fungus Fusarium graminearum

et al. 2013

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Fusarium graminearum (teleomorph Gibberella zeae) is a prominent pathogen that infects major cereal crops such as wheat, barley, and maize. Both sexual (ascospores) and asexual (conidia) spores are produced in F. graminearum. Since conidia are responsible for secondary infection in disease development, our objective of the present study was to reveal the molecular mechanisms underlying conidiogenesis in F. graminearum based on the framework previously described in Aspergillus nidulans. In this study, we firstly identified and functionally characterized the ortholog of AbaA, which is involved in differentiation from vegetative hyphae to conidia and known to be absent in F. graminearum. Deletion of abaA did not affect vegetative growth, sexual development, or virulence, but conidium production was completely abolished and thin hyphae grew from abnormally shaped phialides in abaA deletion mutants. Overexpression of abaA resulted in pleiotropic defects such as impaired sexual and asexual development, retarded conidium germination, and reduced trichothecene production. AbaA localized to the nuclei of phialides and terminal cells of mature conidia. Successful interspecies complementation using A. nidulans AbaA and the conserved AbaA-WetA pathway demonstrated that the molecular mechanisms responsible for AbaA activity are conserved in F. graminearum as they are in A. nidulans. Results from RNA-sequencing analysis suggest that AbaA plays a pivotal role in conidiation by regulating cell cycle pathways and other conidiation-related genes. Thus, the conserved roles of the AbaA ortholog in both A. nidulans and F. graminearum give new insight into the genetics of conidiation in filamentous fungi.

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Section: Introductionmentioning

confidence: 99%

AbaA Regulates Conidiogenesis in the Ascomycete Fungus Fusarium graminearum

et al. 2013

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“…Many abiotic factors have been considered very important in controlling chlamydospore formation in Fusaria (Snyder & Hansen, 1941;Leach, 1962;Nyvall, 1970;Schippers & Old, 1974;Oritsejafor, 1986;Hebbar et al ., 1997;Ciotola et al ., 2000). A factor of high importance appears to be the nutritional status of the medium.…”

Section: Discussionmentioning

confidence: 99%

Influence of Agricultural By-products in Liquid Culture on Chlamydospore Production by the Potential MycoherbicideFusarium oxysporumFoxy 2

Elzein

Kroschel

2004

Biocontrol Science and Technology

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Economically feasible inoculum mass production methods are required for successful application of Fusarium oxysporum Foxy 2 as a potential mycoherbicide. Therefore, different substrates (agricultural by-products) and the factors that influence the production of spores, especially chlamydospores, of Foxy 2 were investigated in liquid cultures. The substrates tested were cotton seed cake, maize stover, wheat and triticale stillage. The presence of plant fibers in the medium of unfiltered cotton seed cake (2.5%, w/v) significantly enhanced chlamydospore, micro-and macroconidia production by 150, 185, and 300%, respectively, compared to the filtered (fiberfree) medium. Regardless of the type of substrate tested, Foxy 2 was able to produce abundant chlamydospores (0.14 Á/2.7 )/10 7 mL (1 ) in all growth media. Generally, increasing the concentrations of cotton seed cake and maize stover in the medium significantly increased chlamydospore formation; however, this was not the case for wheat-based stillage. To optimize conditions required for chlamydospore production of Foxy 2, the effect of near ultra-violet (NUV) light, substrate combinations (synergism), level of agitation, incubation time and their interaction were studied. A liquid culture of 2.5% (w/v) filtered cotton seed cake, exposed to continuous NUV for 15 days, doubled the yield of chlamydospores (4.7)/10 6 mL (1 ) and macroconidia (5 )/10 5 mL (1 ), and increased microconidial production by one-third (1)/10 8 mL (1 ) compared to natural light. An apparent synergistic effect of substrate combination was observed, since the addition of 20% (v/v) of either wheat or triticale-based stillage to maize stover medium (1%, w/v) increased the number of chlamydospores produced by 16 or 12 times, respectively, compared to maize stover alone (1.4 )/10 6 mL (1 ), and 2 times more than either of the stillages. A significantly positive effect between a high level of agitation tested during incubation and chlamydospore production of Foxy 2 was recorded. All in all, substantial chlamydospore production of Foxy 2 (4.3)/10 7 mL (1 ) was successfully achieved within 12 days of incubation in a single-step liquid fermentation through the combination of 0.5% (w/v) maize stover plus 20% (v/v) wheat-based stillage and a high level of agitation (200 rpm).

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“…The pathogen in most instances survived in residues longer than it was able to sporulate on them. Gibberella zeae is known to survive in residues as mycelium or chlamydospores (Nyvall 1970). The inability of surviving mycelium to produce perithecia or macroconidia may arise from depletion of available nutrients in the substrate, a decline in biomass of the pathogen, or from the effects of other organisms in the substrate.…”

Section: Discussionmentioning

confidence: 99%