Observation of vesicular-arbuscular mycorrhizal formation in the roots of some seasonal weeds proliferated in citrus orchards

Weeds were collected from citrus orchards in April and July to investigate vesicular-arbuscular mycorrhizal (VAM) infection. The infection was found to be high in the roots of spring weeds : Rumex acetosa L., Agropyron tsukuhiense (Honda) Ohwi var. transiens (Hack.) Ohwi, Stellaria media Villars., Vicia cracca L., Lamium amplexicaule L., and Medicago polymorpha L., and in the roots of summer weeds : Erigeron canadensis L., Amaranthus lividus L., Cynodon dactylon (L.) Pers., Beckmannia syzigachne (Steud.) Fern., Commelina communis L., Oxalis corniculata L., and Digitaria adscendens Henr. Spore formation was mostly found in the roots of spring weed : Stellaria media, Vicia cracca, and Lamium amplexicaule ; no VAM infection was observed in the roots of Rumex japonicus Houtt., Equisetum arvense L., and Polygonum blumei Meisn.