Variable inhibition of iron uptake by oat phytosiderophore in five soybean cultivars

Abstract

Iron‐efficient Coker 227 oat (Avena byzantina C. Koch.) releases a phytosiderophore in response to Fe‐deficiency stress to solubilize Fe. In previous studies, Fe‐inefficient fefe muskmelon (Cucumis melo L.) and T3238fer tomato (Lycopersicon esculentum Mill.) were able to obtain Fe from phytosiderophore released by Coker 227 oat, while T203 soybean (Gfycine max (L.) Merr.) could not. Could this inability to obtain Fe from phytosiderophore be associated with T203 soybean's severe Fe inefficiency or could it be universal in soybean? This study was conducted to determine whether five soybean cultivars with varying Fe‐efficiency ratings possess the ability to utilize Fe from a phytosiderophore released by Coker 227 oat. These soybean cultivars were grown in either the presence or absence of oat in a buffered, modified Steinberg solution with 1.2 mg L^‐1 Fe. None of the soybean cultivars exhibited increased Fe uptake when phytosiderophore was present in solution, although A7 and Dawson soybean (the most Fe‐efficient cultivars) were able to obtain Fe when in competition with the oat phytosiderophore. Phytosiderophore reduced Fe uptake in the less Fe‐efficient cultivars (T203, Pride, and Corsoy). The degree of inhibition of Fe uptake in the five cultivars was directly related to their known susceptibilities to Fe‐deficiency chlorosis and to their capacities to reduce Fe³⁺ to Fe²⁺ in the rhizosphere.