L.M. Manici, M. Kelderer, F. Caputo, and M. Mazzola
United States Department of Agriculture-Agricultural Research Service (USDA-ARS) Tree Fruit Research Lab, 1104 N. Western Ave., Wenatchee, WA 98801
USDA-ARS Publication # 302122
Plant Pathology, November 2014, Volume 64, Number 4, Pages 843-851 View Full Article
Interpretive Summary: The immediate post-plant period is the time during which newly established fruit trees are most susceptible to biotic and abiotic stresses when planted on sites previously planted to the same or related crop species. Soilborne pathogens resident to these sites which is compromised primarily of a root rot fungal complex, actively attacks young roots causing root death. Thus, the ability to induce enhanced root proliferation of the rootstock in this system has significant potential to reduce the effect of the replant disease pathogen complex on tree growth and productivity. To date, bacteria and mycorrhizal fungi have been the most commonly reported organisms to possess a hormone-based root-inducing activity. There has been little study of the practical use of growth promotion abilities of endophytic fungi as a means to enhance crop development. The evidence reported in this study suggests that there exists potential for utilizing the rooting induction ability of hormone (indole acetic acid; IAA)-producing endophytic fungi as a means to develop cropping practices aimed at increasing soil health and soil suppressiveness in permanent cropping systems such as apple orchards. This strategy is consistent with the IAA production ability observed for most endophytic fungal isolates investigated in this study, as they are endemic to the replanted apple orchard soils. In particular, Fusarium acuminatum, the most promising species based upon its high IAA production and root inducing ability, was isolated frequently from apple roots. the significant increase in dry matter production of plants colonized by F. acuminatum obtained in plant bioassays, suggests that these fungi may represent one of the beneficial plant–microbe interactions responsible for high quality fruit production in several agro-environments.