Arbuscular mycorrhizal fungus infection enhances acclimation of asparagus plantlets derived from tissue culture

Effect of arbuscular mycorrhizal (AM) fungus inoculation on growth of young asparagus (Asparagus officinalis L.) plantlets derived from tissue culture was investigated in order to apply AM fungus inoculation to the acclimation process of tissue culture-derived asparagus plantlets. After 3 weeks of acclimation under regulated conditions using acclimation apparatus, AM fungus (Glomus etunicatum) infection occurred in all of the inoculated asparagus (cv.MW500W) plantlets forming normal roots or semitransparent roots. Survival rates of plantlets and growth increments in both shoots and storage roots in the acclimation period were higher in AM fungus-infected plantlets than in noninoculated ones. After transplanting to new bed soil followed by acclimation, the growth enhancement through symbiosis were subsequently observed. All of 3 asparagus cultivars (cvs. MW500W, Welcome and NJ green) were infected with each of 3 AM fungus species inoculated (Glomus etunicatum, Glomus intraradices and Gigaspora margarita). The survival rates of plantlets and the growth increments in both shoots and storage roots were greater in AM fungus-infected plantlets than in noninoculated ones. AM fungus infection level in a whole root system and the plant growth enhancement through symbiosis varied according to the fungus species-asparagus cultivar combinations. Our results verify that AM fungus might be available for increasing survival rate and promoting initial growth of tissue culture-derived asparagus plantlets during the acclimation process.