Relation between pectic substances and arbuscular mycorrhizal fungus infection in three vegetable crops.

摘要

The relation between the content of pectic substances and arbuscular mycorrhizal (AM) fungus infection in seedling roots of asparagus (cv. MW500W), Welsh onions (cv. Green-negi) and petsai (Brassica campestris cv. Harumaki-gokuwase) was investigatedto seek an effective inoculating method for AM fungus infection. Levels of total pectic substances were higher in storage roots of asparagus, root tips of both asparagus and Welsh onion, and both the secondarily branched root and main root of petsai, which were difficult to infect, than in the easy-to-infect primary feeder roots of asparagus and both the primarily branched root and main root of Welsh onion. Pectic substances in the cortex of the storage root of asparagus and the secondarily branched root of petsai, and in the root tips of both asparagus and Welsh onion become heavily stained with ruthenium red, whereas the cortex of the primary feeder roots of asparagus and both the primarily branched root and main root of Welsh onion did not. The middle lamella and primary cell walls of root tissues were ruthenium red-sensitive. The lack of infection in asparagus storage roots and petsai branched roots is attributed to rich pectic substances in their thick middle lamellae and primary cell walls. Roots were infected with Gigaspora margarita after pectinase [polygalacturonase] treatment prior to inoculation. It was suggested that pectic substances in roots influence infection of AM fungus.