Growth promotion of trifoliate orange [Poncirus trifoliata] seedlings and grape rooted-cutting through an infection of VA mycorrhiza

In order to establish a promising strategy in fruit tree nurseries, the effects of VAM application on seedling growth of trifoliate orange (Poncirus trifoliata Raf., a leading citrus rootstock in Japan) and rooted-cutting growth of grape cultivar 'Black Olympia' were investigated. Trifoliate orange seedlings and grape rooted-cuttings grown in plastic trays filled with river sand were transplanted to Wagner pots, using sterilized volcanic ash soil mixture for the former plants and non-sterilized volcanic ash soil for the latter plants. On transplanting, their roots were treated with an inoculatum which included spores of Glomus mosseae, G. fasciculatum and G. sp. R-10. They were grown in a plastic house and their height was measured sequentially. Fibrous roots of the seedlings and rooted-cuttings were stained by a technique of Phillps and Hayman so that VAM infection could be inspected efficiently. The growth of the seedlings and rooted-cuttings were recorded through checking each dissected parts on fresh and dry weight basis. P content of each part was determined colorimetrically. In VAM treated seedlings and rooted-cuttings, vesicles, arbuscules and internal or external hyphae were observed under an optical microscope. The rate of VAM infection was significantly larger in the treated plants than that in the non-treated ones. VAM treated seedlings and rooted-cuttings showed a 1.5-2.0 fold increase in shoot growth as compared with non-treated control. As a consequence, fresh weight and dry weight of top and root in VAM treated plants were increased significantly. P contents of VAM treated seedlings and rooted-cuttings were greater than those in the non-treated control, and the tendency was clearer in the toots. Another point to be mentioned was that the leaves with brown spots of VAM treated grape rooted-cuttings were less number as compared with the control. Presumably their good effects obtained here became possible through an improved P nutrition and water absorption through VAM infection. A possibility of an effective utilization of VAM in fruit tree propagation was suggested