Pathogenic variability of Fusarium head blight species on durum wheat plants determined using in vitro detached leaf and seedling assays

Abstract

Fusarium head blight (FHB) is an economically important disease of wheat globally, but few publications have appeared on assessing quantitative component of pathogenicity of FHB species in vitro. In this context, the aggressiveness of 16 isolates of four FHB species was quantified on a durum wheat cultivar with a moderate resistance to FHB infection. Two in vitro assays (detached leaf and seedling tests), which yielded six aggressiveness criteria, were used. Results showed differences between treatments inoculated with FHB isolates and control for all tested criteria. Regarding latent period of detached leaf test, variability in aggressiveness within and among the species was detected. The other five criteria: incubation period and lesion length of detached leaf test, percentage of infected seedlings (of foliar-spraying and pin-point inoculations) and lesion length (of clip-dipping inoculation) did not distinguish FHB isolates. Taking into consideration in vitro and the artificial inoculation findings generated under different experimental conditions, significant correlations were found between latent period and these pathogenic indices. Therefore, the idea of using the in vitro criterion: latent period appears to be established based on its predictive ability of aggressiveness occurring at the earliest and latest wheat development stages during FHB infection.