RAPID METHODS FOR QUANTIFYING VAM FUNGAL-INFECTIONS IN MAIZE ROOTS

Roots of maize (Zea mays cv W64A x W182E) infected by vesicular arbuscular mycorrhizal (VAM) fungi (Glomus versiforme (Karst) Berch or a Glomus species isolated from an alfalfa soil) exhibit a bright yellow pigmentation. The percentage of pigmented roots can be quantified by a rapid visual estimate or by a grid intersect method. Both methods gave similar estimates of VAM infection to those obtained using a grid intersect count on cleared roots stained with chlorazol black E. Thus for experimental or field evaluation where speed and quantity are important, the rapid visual estimate (less than one minute for each washed root system) yields reliable results. The yellow root intersect method takes longer (5-15 minutes per root system) but gives more reproducible results. The yellow root pigmentation is light sensitive. However, root systems can be reliably assayed after 1 week when stored at 5-degrees-C in the dark or after 1 year if dried.