A Potassium Phosphite Solution as a Dual-Action Strategy Against Bean Anthracnose: Antifungal Activity and Defense Gene Priming

Anthracnose in bean is an important disease caused by Colletotrichum lindemuthianum, which affects crop productivity and infects the plant in all growth stages, affecting the quality of the pod and grains. The most viable strategy to control this disease is using bean cultivars; however, fungal variability is a limitation. Among the strategy proposed is using phosphite-based compounds, which can act as fungicides or priming stimulators. This study aimed to evaluate the antifungal activity of phosphite base solution (potassium phosphite (H3PO3), potassium hydroxide, and potassium citrate, in a formulation of phosphorus (P2O5) 28% and potassium (K2O) 26%) on C. lindemuthianum under in vitro conditions. In addition, its effects as a defense inducer in Sutagao bean plants, assessing changes in disease severity and the expression of PR1, PR3, PR4, and POD defense-related genes in plants treated with the phosphite solution before infection with the fungus. The results showed the fungicidal effect of potassium phosphite solution on C. lindemuthianum by reducing 42% of the mycelial growth by 48% germination percentage with a dose of 5 mL L-1. The effect of foliar of application of phosphite base solution on anthracnose severity showed a 17% reduction associated with the high expression of PR1, PR3, PR4, and POD defense genes, which increased in plants that were subsequently infected with the pathogen, demonstrating a priming effect. In conclusion, a potassium phosphite solution can be included in a management program to control bean anthracnose.