Impact of Arbuscular Mycorrhizal Fungi on Phosphorus Use Efficiency and Root Diseases of Onion Crops
CSANR Project 137
Onion growers in the semi-arid, irrigated Columbia Basin produce 27% of the storage onions in the USA, with a crop farmgate value ranging from $4,000-$7,000/acre. Symbiotic arbuscular mycorrhizal fungi (AMF) colonize roots of many plant species and help the plants mine soil more effectively for immobile nutrients, particularly phosphorus (P). AMF can also help defend plants against some root pathogens. Onions depend significantly on AMF as the symbiotic association compensates for the relatively sparse, unbranched roots with few root hairs. However, the widespread use of soil fumigation and high rates of P fertilizer used for onion crops in the Columbia Basin may negate or reduce significantly this symbiotic association of onion plants with AMF. The objectives of this proposal are to determine the AMF species and prevalence in organic and conventional onion crops in the Columbia Basin, and to use greenhouse trials as well as grower-cooperator field trials to determine whether inoculation of onion plants with AMF improves onion growth, increases P use efficiency, and/or reduces soilborne disease pressure (particularly Rhizoctonia stunting and other prevalent soilborne diseases of onion such as pink root). A long-term goal is to examine how AMF can contribute to improved soil quality in the Columbia Basin by facilitating reduced use of soil fumigation and soil application of fungicides, as well potential reduced rates of P fertilizers.
Lindsey du Toit
Dipak Sharma Poudyal