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Fusarium head blight (FHB) is a major threat to wheat crop production and food security worldwide. The creation of resistant wheat cultivars is an essential component of an integrated strategy against Fusarium graminearum, the primary aetiological agent that causes FHB. The results of this study show that the deployment of proto-cooperative interactions between wheat genotypes and mycoparasitic biocontrol agents (BCAs) can improve crop yield and plant resistance in controlling the devastating effects of FHB on wheat agronomic traits. A Fusarium-specific mycoparasite, Sphaerodes mycoparasitica, was found to be compatible with common and durum wheat hosts, thus allowing the efficient control of F. graminearum infection in plants. Four genotypes of wheat, two common wheat, and two durum wheat cultivars with varying FHB resistance levels were used in this greenhouse study. The BCA treatments decreased FHB symptoms in all four cultivars and improved the agronomic traits such as spike number, spike weight, seed weight, plant biomass, and plant height which are vital to grain yield. Conversely, the F. graminearum 3ADON chemotype treatment decreased the agronomic trait values by up to 44% across cultivars. Spike number, spike weight, and seed weight were the most improved traits by the BCA. A more measurable improvement in agronomic traits was observed in durum wheat cultivars compared to common wheat. [ABSTRACT FROM AUTHOR]

Seed germination is a critical life stage for plants survival and timely seedling establishment especially in stressful environments. We hypothesized that fungal endophytes would improve wheat seed germination under heat and drought stress. The hydrothermal time (HTT) model of germination is a conceptual model useful for predicting the timing and energy of germination (EG) under a given set of conditions. The HTT and EG are applied, for the first time, to determine if one or more compatible endophytic fungi enhance heat or drought tolerance in wheat. Fungal endophytes tested dramatically increased the percent of germination, improved EG and HTT values, and diminished wheat susceptibility to heat and drought as measured by fresh weight of seedlings. When colonized by the most effective fungal endophyte, the values of the parameters tested in wheat seeds exposed to heat stress resembled those of unstressed seeds. Key words: seed germination, fungal endophytes, abiotic stress, hydrothermal time model, in vitro, wheat. Resume : La germination des graines constitue un stade critique du cycle vital pour la survie des plantes et l'etablissement des plantules au bon moment, surtout dans des milieux stressants. L'auteur emet l'hypothese que les endophytes fongiques amelioreraient la germination des grains de ble sous des stress thermiques et hydriques. Le modele chronohydrothermique de germination (CHT) de germination est un modele conceptuel utile pour predire le moment et l' energie de germination (EG), sous un ensemble de conditions. Pour la premiere fois, l'auteur applique les CHT et EG pour determiner si un ou plusieurs champignons endophytes compatibles augmentent la tolerance a la chaleur et a la secheresse. Les endophytes testes augmentent fortement le pourcentage de germination, ameliorent les valeurs CHT et EG, et diminuent la susceptibilite a la chaleur et a la secheresse sur la base des poids frais des plantules. Suite a la colonisation par les endophytes fongiques les plus efficaces, les valeurs des parametres testes chez les grains de ble exposes au stress thermique ressemblent a celles des grains non stresses. Mots-cles : germination des graines, endophytes fongiques, stress abiotique, modele chronohydrothermique, in vitro, ble. [Traduit par la Redaction], Introduction Increasing evidence suggests that endophytic fungus-plant interactions are an important determinant of plant evolution and biodiversity (Gundel et al. 2010; Davitt et al. 2010). Colonization of host plants by [...]

Sphaerodes mycoparasitica is an ascomycetous mycoparasitic taxon commonly found growing and sporulating on Fusarium pathogens in Canada. Ascospores of S. mycoparasitica failed to germinate under different standard laboratory conditions (sterile distilled water, water agar, and commercially available media), even after heat- and cold-shock treatments. In contrast, spore germination was obtained on commercial potato dextrose agar medium amended with Fusarium filtrates. Significant improvement in the percentage of spore germination was obtained for the spores suspended in Fusarium filtrates. Fusarium avenaceum and Fusarium oxysporum filtrates induced the highest germination, whereas Fusarium sporotrichioides and Fusarium proliferatum triggered lower germination frequency. Filtrates of beneficial fungal inoculants, including Trichoderma harzianum (RootShield®), Penicillium bilaii (JumpStart®), and Chaetomium globosum, had no impact on germination. Ascospore suspensions showed a double-polar germination pattern in F. avenaceum filtrate and single-polar germination when challenged with F. oxysporum filtrate. Sphaerodes mycoparasitica grown on F. oxysporum maintained the same spore germination patterns when transferred on F. avenaceum for three subsequent offspring generations, indicating a stable genome-regulated expression. Preliminary phylogenetic analyses based on large subunit rDNA showed the evolution of a group of mycoparasitic Sphaerodes species from nonmycoparasitic ancestors, but no clear evidence of coevolution or cospeciation between known Sphaerodes and their Fusarium hosts. Key words: biocontrol, biotrophic mycoparasites, Fusarium exudates, Sphaerodes. Le Sphaerodes mycoparasitica constitue un taxon ascomycete mycoparasite se developpant et sporulant frequemment sur des Fusarium pathogenes au Canada. Les ascospores du S. mycoparasitica ne peuvent germer sous differentes conditions standard de laboratoire (eau distillee sterile, eau gelosee et milieux commercialement disponibles), meme apres des traitements-chocs au chaud et au froid. On obtient plutot la germination des spores sur un milieu d'extrait de pomme de terre avec dextrose, additionne de filtrats de spores de Fusarium. On obtient une amelioration significative du pourcentage de germination des spores chez les spores suspendues dans les filtrats de Fusarium. Les filtrats des Fusarium avenaceum et Fusarium oxysporum induisent la plus forte germination, alors que les filtrats des Fusarium sporotrichioides et Fusarium proliferatum produisent des frequences plus faibles de germination. Les filtrats d'inoculums beenefiques comme les Trichoderma harzianum (RootShield®), Penicillium bilaii (JumpStart®), and Chaetomium globosum n'ont aucun impact sur la germination. Les suspensions d ascospores montrent un patron de germination bipolaire dans le filtrat du F. avenaceum et unipolaire lorsque confrontees au filtrat du F. oxysporum.Le Sphaerodes mycoparasitica cultive sur F. oxysporum conserve les memes patrons de germination lorsque transfere sur le F. avenaceum au cours de trois generations de descendants, ce qui indique une expression stable regulee par un genome. Des analyses phylogeenetiques preliminaires basees sur la LSU du rADN montrent revolution d'un groupe d'especes de Sphaerodes mycoparasites provenant d'ancetres non mycoparasites, mais il n'y pas de preuve nette d'une coeevolution ou cospeeciation entre les Sphaerodes et leurs hotes Fusarium. Mots-cles: maitrise biologique, mycoparasites biotrophiques, exsudats de Fusarium, Sphaerodes. [Traduit par la Redaction], Introduction Ascospore germination is a crucial developmental point in the life cycle of Ascomycota. In filamentous fungi, it has been proposed that sexual spore germination follows three important stages: activation, [...]