Influence of Mycorrhizal Fungi on the Mineral Nutrition and Yield of Onion in Saline Soil1

Abstract

AbstractIn a number of studies, salt‐affected plants have been found to contain lower P concentrations than non‐salinized control plants. This study was performed to evaluate the ability of two vesicular‐arbuscular mycorrhizal fungi (VAM) to improve the yield and salt tolerance of onion (Allium cepa L. var. Burpee hybrid 5276) by facilitating P uptake from a saline soil. Onion was grown in a Delhi loamy sand soil (mixed, thermic Typic Xeropsamment) in the glasshouse under ambient light conditions. Plants infected with Glomus fasciculatus and G. monosporus VAM had higher bulb and total onion dry weights than nonmycorrhizal plants in P deficient soil at low (−0.06 MPa bars) irrigation water solute potential (Ψ3), intermediate (−0.20 MPa Ψ3), and high (−0.41 MPa). Plants infected with G. fasciculatus yielded significantly more than G. monosporus plants at low (Ψ3 = −0.06 MPa) and high (Ψ3 = −0.41 MPa) salinity; at Ψ3 = −0.20 MPa bars, yields were not significantly different for mycorrhizal plants. Mycorrhizal infection with both fungi tended to decrease linearly with increasing salinity, although it remained high (58 to 46%) even at high salinity. As salinity increased, nonmycorrhizal plants developed lower concentrations of P, Mg, and K in shoot tissues, K in bulb tissues, with lower total uptake (mg plant−1) of Ca, Mg, K, Zn, and Mn. Mycorrhizal onion had greater concentrations of P and K in shoot tissues, P in bulb tissues, and greater P, Ca, Mg, Na, K, Zn, and Fe total uptake than nonmycorrhizal plants at intermediate soil salinity. Tissues of mycorrhizal plants contained only 70 % as much Mn as nonmycorrhizal plants; high Zn and Fe concentrations were reduced in plant tissues at high salinity compared with intermediate and low salinity. Improved nutritional status of onion plants due to mycorrhizal fungi is at least partially responsible for increased plant growth under saline conditions, although other mechanisms may be involved.