Zinc (Zn) and Iron (Fe) Fertilization for Improving the Antioxidant Enzyme Activity and Biochemical Constituents in Capsicum Hybrids

Micronutrients, particularly Iron (Fe) and Zinc (Zn), play a vital role in the growth and development of plants due to their catalytic effect on many metabolic processes. However, the biochemical responses to the applied micronutrients vary with cultivars and their species. A screening experiment was conducted during 2020 to know the antioxidants enzyme activities and biochemical constituents in response to iron and zinc fertilization by six capsicum hybrids grown in grow bags under shade net conditions. The experiment consists of three treatments viz., Control (No Fe & Zn), 50 kg FeSO4 and 37.5 kg ZnSO4 ha-1 as a basal soil application with six capsicum hybrids viz., Indra, Priyanka, Inspiration, Massilia, Bachata, and Local green. Leaf samples of the capsicum hybrids were collected at Fruiting stage and analysed for antioxidant enzyme activities. The fruit samples were used for quantifying the biochemical constituents. The results revealed that, application of ferrous sulphate (FeSO4) and zinc sulphate (ZnSO4) to capsicum hybrids increased the biochemical constituents in fruits and the antioxidant enzyme activities in leaves. Out of the six hybrids tested, Indra possessed higher ascorbic acid content (9.20 mg 100 g-1 fresh weight), acidity (6.0), and total soluble solids (6.10 Brix) in the fruits, which was followed by Inspiration and Bachata. The superoxide dismutase (6.70 unit’s mg-1 protein) and peroxidase (6.90 unit’s g-1 fresh weight) activities were also higher with the same genotypes. The biochemical constituents and antioxidant  enzyme  response to Zn addition was better than Fe.  There was 13.2, 10.9 and 9.5 per cent increase in titratable acidity, total soluble solids, ascorbic acid content in the fruits of Indra due to ZnSO4 application.The Principal Component Analysis (PCA) and hierarchical clustering revealed that Indra is highly responsive to Zn and Fe fertilization, while the local green showed very less response. The rest of the genotypes such as Inspiration, Bachata, Massilia, and Priyanka, are medium responsive for Zn and Fe fertilization.