Evaluation and standardization of Zinc and Iron biofortification techniques in Milky mushroom (Calocybe indica)

Abstract

Micronutrients and mineral deficiencies in the diet continue to pose serious global health challenges, especially in developing regions. The nutrients especially iron (Fe) and zinc (Zn), are often found to be insufficient in a cereal-based diet. This study evaluated the biofortification potential of the edible mushroom Calocybe indica through substrate supplementation with iron sulphate (FeSO4) and zinc sulphate (ZnSO4) under controlled cultivation conditions at Kerala Agricultural University. Substrates composed of coir pith and vermicompost were enriched with FeSO4 and ZnSO4 at concentrations of 2.5, 5, 10, and 20 mg/kg on a dry weight basis, with a nine-treatment Completely Randomized Design. Iron supplementation at 5 mg/kg FeSO4 significantly enhanced mushroom growth and yield by approximately 18% compared to control and increased iron accumulation in fruiting bodies to 1427 ppm, demonstrating effective bioaccumulation and improved nutritional quality. However, a higher concentration of 20 mg/kg completely inhibited fruiting, indicating toxicity risks at excessive iron levels. Zinc supplementation improved yield notably, with the highest fresh weight at 2.5 mg/kg ZnSO4 (367 g per bag), nearly double to the yield in control, but did not result in statistically significant increases in zinc content within fruiting bodies, likely due to stringent homeostatic regulation and limited zinc translocation under solid-state cultivation. These findings reveal distinct species- and micronutrient specific uptake dynamics in C. indica and highlight the need for tailored biofortification protocols. Substrate-based micronutrient fortification emerges as a cost-effective strategy for producing nutrient enriched mushrooms, with C. indica showing strong potential as a dietary iron source. Future research should focus on alternative zinc formulations, synergistic nutrient interactions, and genetic approaches to optimize zinc bioavailability and accumulation.