Biological control of cryphonectria parasitica with streptomyces and an analysis of vegetative compatibility diversity of cryphonectria parasitica in Wisconsin, USA
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The American chestnut tree (Castanea dentata) has been plagued by the fungal pathogen Cryphonectria parasitica. While the primary biological control treatment has relied upon the use of hypovirus, a mycovirus that reduces the virulence of C. parasitica, here the potential for a Streptomyces inoculum as a biological control is explored. Two Wisconsin stands of infected chestnut in Galesville and Rockland were inoculated with hypovirus and Streptomyces using a randomized block design. At these stands the Streptomyces treatment reduced canker length expansion rates more than the hypovirus treatments and control. The Streptomyces treatment had significantly lower canker width expansion rates compared to the control. In addition to having reduced canker expansion rates, the trees inoculated with Streptomyces had the lowest mortality rate. The diversity of the fungus was low at the study sites and consisted of only two known vegetative compatibility types at each stand. This low level of diversity made it ideal for hypovirus dispersal, and for limiting canker expansion rates. This research supports the hypothesis that Streptomyces treatment is an effective alternative to hypovirus treatment that may prove beneficial in areas where hypovirus efforts have failed.
Castanea -- United States.