Colonization of wheat roots from seed‐applied spores ofIdriella (Microdochium) bolleyi:A biocontrol agent of take‐all

Publisher Website
Google Scholar
Abstract
Wheat seedlings were grown in containers of perlite in a glasshouse, and spores of Idriella bolleyi were applied either to the seeds in alginate gel or to the perlite as aqueous suspensions. Growth and sporulation of the fungus on seeds and roots were assessed by plating methods and by retrieval of spores from water that drained from the plant containers. Idriella bolleyi sporulated heavily on seeds for up to 3 weeks when applied to them in alginate gel, andmost of the root system was infected from newly formed spores that were carried in percolating water. Removal of the inoculated seeds from seedlings at 7 days reduced the degree of root infection and temporarily reduced the number of spores in drainage water; however, spore numbers increased to control levels (seeds attached) by 21 days, indicating subsequent sporulation on the roots. When spores were applied to perlite containing young (0–3 days) seedlings I. bolleyi colonized the seeds, sporulated heavily on them and extensively colonized the roots. However, it established poorly on seeds and roots if added to the perlite when seedlings were 11 days or older. The results suggest that early growth on seeds is necessary for establishment of a high population of I. bolleyi, and that cycles of sporulation on seeds and then roots contribute to colonization of the rhizosphere. The features associated with the rhizosphere competence of I. bolleyi are compared with those for systemic colonization of the xylem by vascular wilt fungi, and suggest a new approach to the selection of root‐colonizing biocontrol agents.