Abstract
AimAgronomic biofortification of fruit with iodine (I) has become an innovative approach in contemporary agriculture. In this study, we evaluated the influence of soil- and foliar I applications on absorption of this nutrient by apple (Malus domestica Borth.) trees, as well as on growth and yield responses of the plants.MethodsIn 2018–2019, ‘Red Jonaprince’ apple trees, grown on sandy loam soil, were treated with potassium iodide (KI) or K-iodate (KIO3) through soil application (at a rate of 4 kg, 8 kg or 12 kg I ha−1) or preharvest sprays (at a rate of 0.5 kg, 1 kg or 1.5 kg I ha−1).ResultsThe I sprays increased apple I contents to the targeted range of 50–100 µg 100 g−1 fresh weight and even to the recommended daily intake of I for adults (the KI sprays at rates of 1 kg and 1.5 kg I ha−1). Although the I sprays caused leaf injuries, they did not affect tree growth and yield. However, the spray of KI and KIO3 at the highest rate decreased the soluble solid concentration in fruit. For soil-supplied trees with I, an increase in apple I concentration was found only in the first year of the study.ConclusionsApple tree is a suitable target plant for agronomic I biofortification, and from the economic point of view, the spray of KI or KIO3 at a rate of 0.5 kg I ha−1 should be recommended in orchards.
Highlights
Iodine (I) is an essential micronutrient for humans at all stages of life mainly due to its incorporation into thyroid hormones that regulate normal growth and development (Arthur and Beckett 1999; Hetzel 1983)
Higher total I concentrations in soil compared with the above combinations were found on IO3−-enriched plots at doses of 8 and 12 kg I ha−1, wherein the use of 12 kg I ha−1 led to the strongest increase in total soil I (5.2 mg kg−1)
The results obtained from the study revealed that under conditions of sandy loam soil with moderate organic matter, the soil treatments of KI or K IO3 at rates from 4 to 12 kg I ha−1 were not highly efficient in increasing I concentrations of ‘Red Jonaprince’ apple trees
Summary
Iodine (I) is an essential micronutrient for humans at all stages of life mainly due to its incorporation into thyroid hormones that regulate normal growth and development (Arthur and Beckett 1999; Hetzel 1983). In I deficiency, endemic goitres appear, and growth, reproductive and mental functions are impaired (Delange 2000; Dillon and Milliez 2000). The above disease complex is termed I deficiency disorder (IDD). To avoid IDD, it is necessary to regularly intake foods with adequate I quantities to cover the recommended dietary allowance (RDA), ranging from 90 μg I d ay−1 for children up to the age of 9 years to 250 μg I day−1 for pregnant and lactating women (Zimmerman et al 2008)
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