Quantification of the arbuscular mycorrhizal fungus Glomus intraradices in host tissue using real-time polymerase chain reaction.

•  A rapid method to quantify the colonization of the arbuscular mycorrhizal fungus (AMF) Glomus intraradices in planta using quantitative real-time polymerase chain reaction (qRT-PCR) technique. •  Specific PCR primers for the fungus (28S rDNA sequence) and host root tissue (chitinase and chalcone synthase gene) were developed and their respective specificity determined. •  The plant specific primers for Lycopersicon esculentum, Medicago truncatula amplified linearly over a concentration range of: 6.4 pg to 20 ng. The G. intraradices-specific primer amplified as low as 1 pg of its target DNA, which allowed us to detect a single spore of the fungus. High degrees of correlation were obtained when threshold cycle (Ct) was plotted against vesicular, hyphal and total colonization using microscopically quantified host roots. •  This is the first report of the application of the qRT-PCR technique for quantification of AMF colonization in planta. The success of its application should open up the possibility of its wider application in AM research.