Are field populations of arbuscular mycorrhizal fungi able to suppress the transmission of seed-borne Bipolaris sorokiniana to aerial plant parts?

Abstract

The development of seed-borne Bipolaris sorokiniana in barley in the presence of arbuscular mycorrhizal fungi was studied. To exploit natural variation in their ability to control disease development, arbuscular mycorrhizal fungi from various Swedish arable soils were multiplied in trap cultures using a mixture of plant species. Six out of eight trap culture soil inocula were able to reduce transmission of B. sorokiniana from seeds to stem bases when grown together with infected barley seed. Based on this result two soil inocula, of different origin, from semi-natural grassland and barley respectively, were chosen for further greenhouse studies. Both soil inocula gave significant reductions in pathogen transmission from seeds to seedlings compared to the untreated control. In addition, treatment with spore inocula, collected from the different trap culture soils, showed disease suppression. Treatment with spores from the pure culture Glomus intraradices gave significant reduction in leaf lesion development. A treatment with the commercial inoculum Vaminoc® was included and gave some suppression of the pathogen. In conclusion this study has shown that AM soil inocula from trap cultures suppressed the transmission of seed-borne B. sorokiniana in the aerial parts of barley plants.