Iron chelates have little to no effect on the severity of Fusarium wilt of bananas in soils of the humid tropics

Abstract

Previous research has shown that application of iron chelates to soil reduces Fusarium wilt in several crop species. The aim of this work was to test the effect for bananas grown in tropical soils. Disease severity and plant characteristics were measured in banana plants (cv. Ducasse, Musa ABB) grown in pots inoculated with Fusarium oxysporum f. sp. cubense, Race 1 in two experiments. Experiment 1 compared amendment with iron chelates (with ligands of differing iron binding stability) with water, plus an uninoculated unamended control, in two tropical Australian soils. Experiment 2 examined the effect of Fe-HBED application rate with high or low calcium addition. In Experiment 1, iron-saturated chelate application did not significantly affect disease severity or plant tissue iron concentration, irrespective of the iron binding stability of the chelate. In Experiment 2, disease severity was not affected by Fe-HBED or calcium application rate. The concentrations of iron and aluminium in plants were both somewhat affected by the addition of Fe-HBED, calcium and their interaction. Fusarium wilt of bananas was not affected by addition of iron chelates to these soils. The lack of effect was likely due to high iron availability in the soils overwhelming the capacity of the treatments to alter iron availability to the host plant and pathogen. Application of strong chelating ligands increased the concentration of aluminium and decreased the concentration of manganese in plant tissue, with possible detrimental effects.