Effects of melatonin and Trichoderma harzianum on pak choi yield, chlorophyll contents and antioxidant defense system under clubroot disease

Abstract

Clubroot disease causes significant damage to cruciferous crops worldwide, resulting in severe decrease in plant yield. Plants tolerate biotic stresses through various mechanisms, including pathogen-associated molecular patterns (PAMPs) that activate immunity and plant resistance proteins. However, humans often resort to non-ecofriendly methods such as chemical applications to control biotic stresses. Melatonin (N-acetyl-5-methoxytryptamine) and Trichoderma are environmentally friendly and cost-effective alternative strategies to protect plants from pathogen attacks. Additionally, they have favorable effects on horticultural crop growth, fruit ripening, flowering, and provide stress resistance to abiotic and biotic diseases. In the present study, we aimed to control clubroot disease in Pak choi through single and combined exogenous application of melatonin and Trichoderma. We analyzed their effects on plant biomass, chlorophyll contents and observed alterations in their antioxidant system. Our results demonstrated that the combined application of 50 µM melatonin and 100 g Trichoderma efficiently control clubroot disease up to 74.85% compared to plants only supplemented with Plasmodiophora brassicae, as indicated by the disease index. Furthermore, we observed increased plant growth and antioxidant enzyme activities, including Ascorbic acid peroxidase (APX), superoxide dismutase (SOD); catalase (CAT), glutathione reductase (GR), and peroxidase (POD). Additionally, malondialdehyde (MDA) and hydrogen peroxide (H2O2) levels were reduced. Moreover, increased levels of chlorophyll, carotenoids and plant biomass have been observed in plants co-inoculated with melatonin and Trichoderma application. These findings provide valuable insights that can be utilized to enhance crop stress tolerance in challenging environments and increase plant yield. The use of environmentally friendly and cost-effective alternatives to chemical control can help mitigate the damage caused by clubroot disease to cruciferous crops.