Phosphonates and SAR-trigger elicitors reducing the intensity of white mold in common bean

Abstract

White mold caused by the fungus Sclerotinia sclerotiorum is one of the main common bean diseases. The aim of this study was to evaluate the effect of phosphonates and elicitors in reducing the severity of white mold. The experiment was carried out in a randomized block design with six treatments and six replications in a split-plot, where each experimental plot consisted of one bean plant. The treatments were acibenzolar-S-methyl—ASM (500 g L−1) 0.25 g L−1, chitosan (85% deacetylation) 50 mg L−1, fluazinam (500 g L−1) 120 g L−1, copper phosphite (275 g L−1) 250 g L−1, and copper ethylphosphonate (20% P2O5 + 1.75% S + 3.5% Cu) 5 mL L−1 and control. Inoculation was performed 28 DAS, and assessment of disease severity was conducted 8 days after inoculation (DAI) using a grade scale. The parameters evaluated were photosystem II (PSII) quantum yield (Fv/Fm) and total chlorophyll content 3, 6, and 9 days after application (DAA) of the chemicals and 3, 6, and 8 DAI. Statistical analyses were performed using R Statistical Software. The phytosanitary chemicals herein evaluated promoted lower intensity of S. sclerotiorum infection in common bean plants compared to the control. No decrease in chlorophyll content was observed, but there was a reduction in Fv/Fm values in inoculated plants compared with uninoculated plants caused by S. sclerotiorum infection, which resulted in damage to the photochemical step of photosynthesis. In this sense, the tested phosphonates and elicitors, especially ASM and copper ethylphosphonate, enhanced protection and reduced disease severity.