VARIATION IN AGGRESSIVENESS OF FUSARIUM HEAD BLIGHT SPECIES TOWARDS BARLEY PLANTS DETERMINED USING THREE IN VITRO ASSAYS

Abstract

Aggressiveness is the most important fungal trait affecting Fusarium head blight (FHB) disease invasion and stability of host resistance. Until recently, in vitro methodologies have proved to be very useful in analyzing disease responses in barley plants to FHB infection. To update our knowledge, the variation in aggressiveness for 16 isolates of four FHB species was assessed towards two barley cultivars varying in resistance to FHB. Nine aggressiveness criteria involved in three in vitro assays were used: incubation period, latent period (LP), lesion length (of detached leaf and clip-dipping inoculations), germination rate reduction, standardized area under disease progress curve (AUDPCstandard), coleoptile length reduction of Petri-dish inoculation, and percentage of infected seedlings (of foliar-spraying and pin-point inoculations). Differences in inoculated treatment were observed on young plant parts relative to water controls. Inter and intraspecific differences in aggressiveness were observed towards barley plants as measured by LP and AUDPCstandard. Nevertheless, the other seven criteria did not differentiate FHB isolates. Results indicted that a cultivar-specific aggressiveness do not exist among barley plants and pathogens for LP and AUDPCstandard. Significant correlation coefficients were obtained between the data of LP and AUDPCstandard. Moreover, the values of LP and AUDPCstandard were significantly correlated with the data of disease incidence generated under controlled and field conditions. It seems that LP and AUDPCstandard are indicators of aggressiveness occurring in the whole plant during FHB infection. To our best knowledge, this is the first in vitro research full analyzing aggressiveness of four FHB species on barley plants. In addition, our study investigates the potential use of in vitro indices in predicting FHB data generated under controlled and field conditions.