Assessing the progress of colonization by arbuscular mycorrhiza of four plant species under different temperature regimes

To capitalize on the benefits offered by arbuscular mycorrhizal fungi (AMF) in agricultural systems the effect of low soil temperature has to be taken into consideration over large areas of the planet. However, the effect of suboptimal root zone temperatures on AMF colonisation is poorly understood. It has been suggested that it depends on the host plant species. We hypothesized that this interdependence is a function of the parameter used to assess the presence of AMF in the roots. In a pot experiment with non-sterilized soil, we investigated the influence of three soil temperatures (10, 15 and 20 ºC) on the progress of root colonisation of four host plant species (Ornithopus compressus, Lolium rigidum, Triticum aestivum and Zea mays) by indigenous AMF. Plant root density, arbuscular colonisation rate (AC) and colonised root density (CRD) were assessed 14, 28 and 42 days after sowing. Based on CRD, the effect of temperature on the progress of root colonisation by AMF was independent of the host plant species. The apparent influence of the host plant species was only due to the species -specific effect of soil temperature on root growth and therefore on AC. The host plant species only determined the minimum temperature for the AM colonisation initiation, possibly due to species-specific response of root growth and exudation to cool temperatures