In this study, the biocontrol ability and colonization behavior of a highly antagonistic Streptomyces mutabilis
strain, named IA1, recently isolated from a Saharan soil, were assessed on wheat seedlings. In this study we
showed that strain IA1 secretes IAA and GA3 and is able to enhance growth of wheat seedlings. Using DOPEFISH
coupled with confocal laser scanning microscopy (CLSM), we observed moreover that following caryopsis
inoculation and plant growth the strain can colonize the rhizoplane, the surface of caryopsis as well as the
endorhiza, crossing from the rhizodermis up to the vascular system. Interestingly, further visualizations revealed
that the actinobacterial strain could also be endophytic inside the caryopsis up to the endocarp layer (the dried
fruit part, not the seed part of grain). Disease caused by Fusarium culmorum was further evaluated on seedlings
and results showed that coated seeds with strain IA1 can reduce both disease occurrence (64.7%) and decrease
severity (79.6%). This study showed that strain IA1 derived from a Saharan soil could protect a temperate crop
from F. culmorum seedling blight, promote growth and colonize various niches on the surfaces of the phytosphere
(roots, seeds) as well as plant endosphere compartments.