Abstract
Sclerotinia stem rot, which is caused by the fungal pathogen Sclerotinia sclerotiorum, is a soybean disease that results in enormous economic losses worldwide. The control of S. sclerotiorum is a difficult task due to the pathogen’s wide host range and its persistent structures, called sclerotia. In addition, there is lack of soybean cultivars with medium to high levels of resistance to S. sclerotiorum. In this work, kojic acid (KA), a natural bioactive compound commonly used in cosmetic industry, was evaluated for the management of Sclerotinia stem rot. Interestingly, KA showed strong antifungal activity against S. sclerotiorum by inhibiting chitin and melanin syntheses and, subsequently, sclerotia formation. The antifungal activity of KA was not obviously affected by pH, but was reduced in the presence of metal ions. Treatment with KA reduced the content of virulence factor oxalic acid in S. sclerotiorum secretions. Preventive applications of 50 mM KA (7.1 mg/ml) completely inhibited S. sclerotiorum symptoms in soybean; whereas, in curative applications, the combination of KA with prochloraz and carbendazim improved the efficacy of these commercial fungicides. Taken together, the antifungal activity of KA against S. sclerotiorum was studied for the first time, revealing new insights on the potential application of KA for the control of Sclerotinia stem rot in soybean.
Highlights
This decrease has been mainly attributed to yield losses produced by soybean diseases, such as Sclerotinia stem rot, which is caused by Sclerotinia sclerotiorum (Willbur et al, 2018; Zhang et al, 2019)
kojic acid (KA) at 15 mM slightly reduced the mycelial growth of B. dothidea, C. brevisporum, and V. pyri, this concentration of KA inhibited completely the growth of S. sclerotiorum (Figure 1A), whereas 5 and 10 mM KA reduced S. sclerotiorum growth by 29 and 56%, respectively (Supplementary Figure S2)
These results indicated that S. sclerotiorum is more sensitive to KA in comparison to the other fungal species used in the assay
Summary
Glycine max (Fabaceae: Phaseoleae), is extensively cultivated in China, United States, Brazil, and Argentina (Ding et al, 2021; Hu et al, 2021). The global soybean production in 2017 was 359.5 million tons; soybean production declined to 333.7 million tons in 2019 [Food and Agricultural Organization of the United Nations (FAO), 2019] This decrease has been mainly attributed to yield losses produced by soybean diseases, such as Sclerotinia stem rot, which is caused by Sclerotinia sclerotiorum (Willbur et al, 2018; Zhang et al, 2019). Apart from the low efficacy of commercial fungicides, the management of S. sclerotiorum is a difficult task due to the pathogen’s wide host range, and its persistent resting structures, called sclerotia. These are known to play important roles in fungal life and disease development cycles (Xia et al, 2020; Tian et al, 2021). The antifungal properties of KA were evaluated as a new low cost alternative for S. sclerotiorum disease management
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