Physiology and ecology of Idriella bolleyi, a biological control agent of cereal root and stem base pathogens

• Main Author: Douglas, Lisa Iris
• Format: Dissertation
• Language: English
• Published: University of Edinburgh 1996

Idriella bolleyi strains, T560, J10 and AB1, differed considerably in their tolerance to water-stress - this was apparent in both osmotic and matric potentials and in all aspects of their growth cycle. The level of tolerance for one strain, T560, was comparable to the take-all pathogen Gaeumannomyces graminis var. tritici, which is associated with low water-stress tolerance, and another strain, AB1, was comparable to the foot-rot pathogen Fusarium culmorum, known to be highly tolerant of drought conditions. Variation in response to osmotic potential was also observed in root and stem base field isolates of I. bolleyi. The field isolates differed in the level of mycelial growth and sporulation at potentials of -1.5 MPa (control) and -5.0 MPa. Isolates from the same plant were found to have different levels of sporulation - this may have been related to the degree of microcycle conidiation they exhibited. Idriella bolleyi isolates, T560 and AR1, were able to colonise straw in soil at different matrix potentials down to -7.0 MPa. Straw colonisation was found to increase from 2 to 8 weeks, indicating that both strains were actively growing at all water potentials during this period. A number of other fungal species were isolated from the straw along with I. bolleyi, suggesting that a high degree of competition was associated with colonisation. Water potential appeared to be the most influencing factor with regard to the activity of each species. Idriella bolleyi could increase its population on unsterilised wheat seeds buried in soil. Idriella bolleyi was inoculated onto the seeds as either an alginate or water suspension. For both seed treatments the detectable level of conidia increased exponentially on the seeds over five days, this increase coinciding with the production of young wheat roots. As the seed aged the detectable level of conidia decreased.