GREAT AT SMALL THINGS

Most Probable Number assay

The objective of this bioassay is to evaluate the number of infective propagules of arbuscular mycorrhizal fungi (AMF) in a specific substrate using the Most Probable Number (MPN) method.

The MPN method involves taking the original sample, diluting it by orders of magnitude (frequently 10×, 4x, 2×), and assessing the presence/absence of colonization in roots of trap plants.

 

The method consist in growing plants on a dilution series of the substrate and assessing the presence/absence of contact points between germinating hyphae and plant.

In practice:

  • Plants are grown during at least 6 weeks under controlled conditions.

  • Roots are then harvested, stained (Walker 2005) and observed under microscope to record the number of plants showing presence of AMF.

  • The MPN is then estimate using a mathematical model (Jarvis et al. 2010).

 

Contact: Sylvie Cranenbrouck

 

Literature:

Ficher and Yates, 1943 Statistical tables for biological, agricultural and medical research. Oliver and Boyd, 6th edition, 1943.

Jarvis B, Wilrich C, Wilrich P-T 2010 Reconsideration of the derivation of Most Probable Numbers, their standard deviations, confidence bounds and rarity values. Journal of Applied Microbiology 109: 1660-1667.

Walker C 2005 A simple blue staining technique for arbuscular mycorrhizal and other root-inhabiting fungi. Inoculum 56(4).

Adelman MJ, Morton JB 1986 Infectivity of vesicular-arbuscular mycorrhizal fungi: Influence of host-soil diluent combinations on MPN estimates and percentage colonization. Soil Biol Biochem 18: 7-13.

Alexander M 1965 Methods of Soil Analysis, Part 2, Agronomy Series #9, ASA, Madison, Wisconsin, pp. 1467-1472.

Alexander M 1982 Most Probable Number Method for Microbial Populations, in Methods of Soil Analysis, Part 2. Chemical and Microbiological Properties, A. L. Page. American Society of Agronomy, 2nd edition, 1982.

Wilson JM, Trinick MJ 1982 Factors affecting the estimation of numbers of infective propagules of vesicular arbuscular mycorrhizal fungi by the most probable number method. Aust J Soil Res 21: 73-81.