Riboflavin alleviates the occurrence of anthracnose caused by Colletotrichum gloeosporioides in postharvest mango and the possible mechanisms involved

Colletotrichum gloeosporioides is a major pathogenic fungus that causes anthracnose in stored mangoes, and it exhibits higher pathogenicity compared to Colletotrichum acutatum. This study primarily investigates the mechanism by which riboflavin prevents mango anthracnose caused by Colletotrichum gloeosporioides. In vitro experiments demonstrated that a concentration of 1.0 mmol L-1 riboflavin exhibited a strong inhibitory effect on spore germination of Colletotrichum gloeosporioides strains isolated from different major mango-producing regions in China, surpassing the efficacy of the chemical agent pyrimethanil. Furthermore, mango fruits infected with Colletotrichum gloeosporioides and treated with 1.0 mmol L-1 riboflavin exhibited a significant reduction in disease index. The mechanism behind this is that riboflavin not only generated reactive oxygen species (ROS) but also induced the production of ROS in the fruit during the early stages of storage, directly killing Colletotrichum gloeosporioides. Additionally, riboflavin activated phenylalanine ammonia lyase (PAL) and peroxidase (POD), leading to the production of total phenols and lignin, enhancing the fruit's disease resistance. Riboflavin also increased the activity of β-1,3-glucanase (GLU) and chitinase (CHI), which can disrupt the cell wall of Colletotrichum gloeosporioides. Moreover, riboflavin enhanced the activity of superoxide dismutase (SOD) and catalase (CAT) in the fruit, reducing weight loss percentage and minimizing the degradation of total soluble solids (TSS). These findings highlight the efficacy of riboflavin in preventing and controlling mango anthracnose.