Effect of arbuscular mycorrhizal fungus inoculation on growth of apple (Malus ssp.) seedlings

Abstract

The means of enhancing the growth of seedlings of apples, Malus pumila Mill. var. domestica Schneid. (cv. McIntosh, American Summer Pearmain, Jonathan, Golden Delicious, Starking Delicious, Fuji, Mutsu and Red Gold) and Malus sieboldii Rehd., through inoculation of arbuscular mycorrhizal (AM) fungus [Glomus etunicatum (GE) and Gigaspora margarita (GM)] were investigated. Eight weeks after inoculation, AM fungus infection occurred in all combinations of apple cultivars and fungus species. The rate of AM fungus-infected portions in a whole root system were; 31.7% in 'Golden Delicious', 50.5% in 'Jonathan' in GE-inoculated plants, and 24.0% for Malus sieboldii Rehd., and 50.7% in 'Starking Delicious' in GM-inoculated ones. Plant height and dry weights of top and roots were greater in all GE-infected seedlings than in noninoculated ones. The GM-infected seedlings made larger height and weight increments than did the noninoculated ones in all seedlings except those of 'Golden Delicious' and Malus sieboldii Rehd.. In 'McIntosh' seedlings, plant growth enhancement through symbiosis clearly appeared associated with both fungi. With both fungal species, P concentrations in the top or roots were higher in infected plants than in noninoculated plants; the effect appeared more noticeably in roots than in top. Consequently, it was confirmed that GE and GM infections and their plant growth enhancement through symbiosis with the seedling stage in several apple cultivars.