Detection of fungi in planta: effectiveness of surface sterilization methods

The effectiveness of surface sterilization methods were compared using root tissue of barley (Hordeum vulgare) colonized by two Chaetomium species in an aseptic plant growth system. The reliability of different sterilants to inhibit ascospore germination was test-ed. Ascospores on nitrocellulose mem branes were either treated directly or ascospores adhering to axenic barley seedlings were treated on plant tissue. Inhibition of ascospore germinatio n on nitrocellulose membranes was achieved with lower concentrations of ste rilants than when the spores were on plant surfaces. A 10% peracetic acid t reatment was necessary if experiments were conducted ad planta. The sterila nts penetrated into epidermal root tissue and caused damage to this area, a s shown by the vital dye DiOC(7)(3). It was concluded that effective surfac e sterilization techniques for ascospores adhering superficially to plant t issue were not appropriate for the detection of fungi growing within the ep idermis.