Influence of Mycorrhizal Fungi and Water Stress on Growth and Yield of Two Onion Cultivars

A field study was conducted to determine the effect of arbuscular mycorrhizal (AM) fungi inoculation on bulb yield and mineral acquisition of two onion (Alium cepa L.) cultivars (Giza 20 and Texas Grano) grown under well-watered and water-stressed conditions. Onion seedlings were transplanted into planting furrows after treatment with or without the AM fungi Glomus mosseae or G. fasciculatum. Root colonization with AM fungi occurred in both cultivars under water-stressed and water-watered conditions, but the extent of AM fungi root colonization was higher under well-watered than under water-stressed conditions. Water stress had significantly reduced bulb yields and mineral acquisition in both cultivars either inoculated or un-inoculated plants. However, inoculation with AM fungi has improved onion bulb yield and mineral acquisition (P, Cu, Fe and Zn concentration) irrespective soil moisture. The results indicated that Texas Grano cultivar benefited more than Giza 20 cultivar from AM fungi inoculation especially under water-stressed conditions. The improved yield and mineral acquisition due to AM fungi inoculation demonstrated the importance of mycorrhizal inoculation to reduce the effects of drought stress on onion grown under field conditions in dry and semi-dry areas. (author)