Nickel potentiates soybean resistance against Sclerotinia sclerotiorum infection

Abstract

White mold, caused by the fungus Sclerotinia sclerotiorum, is one of the most destructive diseases on soybean worldwide and deserves attention regarding its management. In this regard, the hypothesis that spraying nickel (Ni) on soybean plants could increase their resistance against white mold, considering its involvement in the catalytic process of several enzymes and as a constituent of many biomolecules, was investigated. The photosynthetic performance (chlorophyll (Chl) a fluorescence parameters and photosynthetic pigments pools (chlorophyll a + b and carotenoids), concentrations of malondialdehyde (MDA), phenolics, and lignin as well as the expression of defense-related genes [phenylalanine ammonia-lyase (PAL1.1, PAL1.3, PAL2.1, and PAL3.1), chitinase (CHIA1), chalcone isomerase (CHI1B1), lipoxygenase (LOX7), metalloproteinase (MMP2), isochorismate synthase (ICS1 and ICS2), urease (URE), pathogenesis-related protein 1 (PR-1A), and nitrate and nitrite reductase (NIR1-1 and INR-2)] were assessed in plants noninoculated or inoculated with S. sclerotiorum and non-sprayed or sprayed with Ni. Mycelial growth of S. sclerotiorum was inhibited by Ni in vitro. White mold severity for Ni-sprayed plants decreased due to higher foliar Ni concentration, less MDA concentration, a great pool of photosynthetic pigments, and a more preserved photosynthetic apparatus compared to plants non-sprayed with Ni. Higher concentrations of phenolics and lignin linked to up-regulation of PAL1.3, PAL2.1, PAL3.1, CHI1B1, and PR-1A genes for Ni-sprayed plants were important to increase their resistance against white mold. These results highlight the potential of Ni for white mold management in the context of more sustainable agriculture that must prize adequate plant mineral nutrition.