Fusarium species causing head blight in wheat and barley show no vertical races

Abstract

On a global scale, Fusarium head blight (FHB) is one of the most noxious diseases of wheat and barley. One or two Fusarium species out of 17 pathogens implicated in the complex FHB disease do not have vertical races following infection in bread wheat; however, no reports support this observation in durum wheat and barley. To end this, 16 fungal isolates of varying aggressiveness of four Fusarium species were tested on eight bread and durum wheat and barley cultivars covering a wide range from moderate resistance to susceptibility. Nine pathogenic components obtained under in vitro, growth chamber and field conditions were measured to determine whether true vertical races exist within the four tested Fusarium species. Although combined analysis of bio-experiments showed that isolate × cultivar interactions were significant, this relationship was unstable over experiments. However, the tested three bread wheat, three durum wheat and two barley cultivars showed consistent resistance to fungal isolates within each tested species, showing that F. culmorum, F. solani, F. verticillioides, and F. equiseti do not have vertical races. Our data concluded that the resistance to FHB in wheat and barley was of the horizontal and non-species specific type. There was no signal for any vertical genes in all tested Fusarium species. Consequently, the resistance genes in sources presently employed in breeding programs are not expected to succumb to new FHB races in the near future. To our best knowledge, this is the first report to show the absence of vertical Fusarium races upon infection durum wheat and barley, and is harmony with earlier reports conduced with bread wheat infected with F. graminearum and F. culmorum.