Inoculation strategies to assess biological interactions betweenFusariumandAlternariaspecies infecting sorghum

Abstract

New cultivars of sorghum are being developed for increased food use, as livestock feed, and for the bioenergy industry by manipulation of secondary metabolic pathways through breeding. Previous work has suggested that such modifications may have an impact on cultivar response to fungal pathogens. We investigated four inoculation strategies that may be used in studies involving pathogens of sorghum. Plants of elite sorghum genotypes 'Wheatland' and RTx430, commonly used in breeding programs, were inoculated with isolates of Alternaria alternata, Fusarium equiseti, Fusarium proliferatum, Fusarium solani, Fusarium thapsinum, and Fusarium verticillioides recovered from field-grown sorghum. Wound inoculation of the peduncles of heads at anthesis demonstrated that isolates of F. verticillioides and F. thapsinum produced mean lesion lengths that were significantly greater than control inoculations. The length of this assay was decreased by inoculating fungi onto plants of a very early maturing sorghum line (N247). Spraying heads at anthesis with conidial suspensions over three consecutive days in the greenhouse was conducted to attempt to mimic conditions in the field. Results indicated that plants treated with conidia of F. thapsinum may develop mature grain with reduced germination. Seed and seedling inoculations produced responses over a relatively short time period. Seed inoculations were conducted in a manner similar to a corn bioassay. Seedling inoculations, conducted in Magenta vessels, allowed for measurement of effects of inoculum on roots, stalks, and leaves. Following inoculation of RTx430 and 'Wheatland' plants grown in Magenta vessels with F. thapsinum, nearly all measurements were significantly different from those of the water controls except for percent root infection of RTx430. Résumé : De nouveaux cultivars de sorgho plus productifs sont à l'heure actuelle développés par manipulation des voies métaboliques secondaires durant le processus de sélection. Ces nouveaux cultivars sont destinés à l'alimentation des humains, à celle du bétail ainsi qu'à l'industrie des bioénergies. Des travaux précédents ont suggéré que de telles modifications peuvent influencer la réponse des cultivars quant à leur résistance aux agents pathogènes fongiques. Nous avons étudié quatre stratégies d'inoculation qui peuvent être utilisées dans les études relatives aux agents pathogènes qui s'attaquent au sorgho. Des plants de génotypes élites de sorgho 'Wheatland' et RTx430, communément utilisés dans les programmes de sélection, ont été inoculés avec des isolats d'Alternaria alternata, de Fusarium equiseti, de Fusarium proliferatum, de Fusarium solani, de Fusarium thapsinum et de Fusarium verticillioides obtenus de plants de sorgho cultivés en champs. L'inoculation de blessures causées aux pédoncules des épis arrivés au stade de l'anthèse a démontré que les isolats de F. verticillioides et de F. thapsinum produisaient des lésions dont les longueurs moyennes étaient passablement plus grandes que celles produites par les inoculation...

Response of Fusarium thapsinum to Sorghum brown midrib Lines and to Phenolic Metabolites

“…Pathogens pose a serious threat to the economic sustainability of grain or biomass production for bioenergy (23,54). Panicle pathogens can negatively impact grain yield, quality, and viability (10,17,32). Root, stalk, and leaf pathogens can reduce biomass yield and cause lodging, which impairs harvest (12,47).…”

Isolation and characterization of the grain mold fungiCochliobolusandAlternariaspp. from sorghum using semiselective media and DNA sequence analyses

“…Fungal species commonly isolated from sorghum grain were grown for production of conidia. To represent a common Fusarium grain pathogen, isolate M-3790 (Fusarium Research Center, Pennsylvania State University, University Park, Pennsylvania), which was identified morphologically (Klittich et al 1997) and molecularly (Funnell-Harris and Pedersen 2008) as F. thapsinum (teleomorph G. thapsina), was used. Throughout the manuscript, this isolate will be known by the more familiar F. thapsinum.…”

“…Alternaria sp. grain isolate H02-781S-3b, which was isolated at Lincoln, Nebraska (Funnell-Harris and Pedersen 2008), was used to represent Alternaria spp. To represent Cochliobolus isolates, LP09-1, which was previously identified morphologically as C. lunata (Little and Magill 2003) (teleomorph Co. lunatus), was used.…”

“…Previous studies had utilized DCPA for root isolations because PCNB medium had been considered too harsh when applied with some plant tissues (Funnell-Harris and Pedersen 2008; D.L. Funnell-Harris and J.F.…”

“…Keissl. 1912;andCurvularia lunata (Wakker) Boedijn 1933 (teleomorph Cochliobolus lunatus Nelson &Haasis 1964) (Funnell-Harris and Pedersen 2008;Funnell-Harris et al 2010;Lincy et al 2011;Navi et al 2005;Sharma et al 2011;Tarekegn et al 2006).…”