Brassicaceae are well known as non-arbuscular mycorrhizal (AM) host plants. This study was aimed to examine effects of two Brassica; cabbage (Brassica oleracea L. cv. cabitata) and mustard (B. juncea Coss.) on three AM species (Acaulospora, Entrophospora and Glomus) and to examine effect of root incorporation into soil on root AM infectivity in maize growing in iron toxicity soil. Experiment 1, cabbage and mustard crop reduced spore density of Acaulospora, but there was no effect on spore density of Entrophospora. While, mustard crop had more effect on Glomus spore density than cabbage crop. Experiment 2, AM spore from two conditions; without and with 6 weeks of root residues (cabbage, mustard and maize) incorporation was examined for its infectivity in maize roots. At D21, without root incorporated, the infectivity of Acaulospora, Entrophospora and Glomus were not different. By contrast, cabbage and mustard root incorporation depressed infec-tivity of Acaulospora but, there was no effect on Entrophospora. Whereas, cabbage root incorporation only depressed infectivity of Glomus. However, AM infectivity was recovered at D42. These results suggested that Brassica root incorporated into soil was the actual effect on the viability of AM spore resulting in reduction of AM infectivity at the early stage.