Abstract
The means of inoculation with arbuscular mycorrhizal (AM) fungi for the production of Welsh onion (Allium fistulosum L., cv. Choetsu) as plug seedlings was investigated. AM fungal infection occurred in all the inoculated seedlings but the infection level in a root system differed with AM species, growth medium, phosphorus concentration in liquid fertilizer, and number of plants in a cell. Growth promotion (increase in dry weight) of shoots and roots occurred as the result of AM fungal symbiosis. The effect and enhancement of root ball formation depended on the following conditions : growth medium consisting of brown peat and vermiculite (9 : 1, v/v), the presence of the AM fungus, Gigaspora margarita, 3 or 4 plants per cell in a 200-cell tray, and 5ppm KH2PO4 in the liquid fertilizer. Welsh onion seedlings, infected with Gigaspora margarita, continued to grow rapidly after being transplanted to a new bed soil. These results reveal that AM fungus inoculation is essential for obtaining vigorous Welsh onion seedlings in a short period and for enhancing the initial growth of transplants in a plug seedling system.
