Microwave radiation as an alternative for controlling Colletotrichum in bean seeds

Anthracnose, caused by Colletotrichum lindemuthianum (Sacc. & Magnus) Briosi & Cavara, is one of the most damaging diseases affecting common bean (Phaseolus vulgaris L.), often transmitted through infected seeds. While fungicide-based chemical control is widely used, it poses risks such as the emergence of resistant strains and negative environmental impacts. In this context, microwave radiation has emerged as a promising physical method for sustainable seed disinfection. This study aimed to evaluate the effects of microwave radiation on the incidence of C. lindemuthianum and on the physiological quality of artificially inoculated bean seeds. Two frequencies (2450 and 1225 MHz) and three exposure times (30, 45, and 60 seconds) were tested, along with an untreated control. Results showed that longer exposure times, particularly at 2450 MHz, significantly reduced pathogen incidence - most notably in the 60second treatment, which brought infection rates below 2%. However, these same conditions resulted in total seed mortality and compromised germination. In contrast, the treatment at 1225 MHz for 30 seconds achieved a more favorable balance, reducing fungal incidence while maintaining germination rates above 70%. These findings indicate that although microwave radiation is highly effective in suppressing C. lindemuthianum, careful optimization of treatment parameters is essential to preserve seed viability and ensure practical application.