Sensitivity and biochemical characteristics of Sclerotinia sclerotiorum to propamidine

https://doi.org/10.1016/j.pestbp.2016.05.006Get rights and content

Highlights

  • We established the baseline sensitivity of Sclerotinia sclerotiorum to propamidine;

  • Evaluated the potential value of propamidine against S. sclerotiorum in pot experiments;

  • Explored the effect of propamidine on the biochemical characteristics of S. Sclerotiorum.

Abstract

Propamidine is an aromatic diamidine compound. In the current study, baseline sensitivity of Sclerotinia sclerotiorum to propamidine was determined using 78 strains collected from the oilseed rape fields without a previous history of propamidine usage. The median effective concentration (EC50) values for propamidine inhibiting mycelial growth ranged from 0.406 to 3.647 μg/mL, with a mean of 1.616 ± 0.217 μg/mL. There was no correlation between sensitivity to propamidine and sensitivity to dimethachlon or carbendazim. After treated with propamidine, mycelia were thinner with irregular distortion and more branches; cell wall became thicker with uneven distribution of cytoplasm than untreated control. In addition, sclerotia production, cell membrane permeability and oxalic acid content significantly decreased. On detached oilseed rape leaves, propamidine exhibited better control efficacy than carbendazim at the same concentration whether the leaves were inoculated with carbendazim-sensitive or resistant strains. All the results showed that propamidine exhibited strong antifungal activity and potential application in controlling S. sclerotiorum. Importantly, these data will provide more information on understanding the mode of action of propamidine against S. sclerotiorum and should be valuable for development of new antifungal drugs.

Section snippets

1. Introduction

The filamentous ascomycete fungus Sclerotinia sclerotiorum (Lib.) de Bary is a necrotrophic plant pathogen with a broad host range and a worldwide distribution [1], [2]. The fungus is highly destructive and capable of infecting more than 400 species of plants from at least 270 genera and 75 families throughout the world. Many economically important crops and vegetables such as common bean, oilseed rape, soybean, sunflower, canola, peanut, cabbage, and lettuce can be infected [3], [4], [5].

2.1. Fungicides and media

Propamidine (97.0%) in technical grade was provided by the Research & Development Center of Biorational Pesticide in Northwest Agriculture and Forestry University (Shaanxi Province, China). Dimethachlon (90.0%) in technical grade was provided by Wenzhou Pesticide Factory (Zhejiang Province, China). They were dissolved in methanol (> 99.5%) to 10 mg/mL for stock solution. Carbendazim (98.0%) in technical grade was provided by Shenyang Academy of Chemistry and Industry (Shengyang, China) and was

3.1. Baseline sensitivity to propamidine

A total of 78 S. sclerotiorum strains which had not been exposed to propamidine were tested on PSA plates for their sensitivity to propamidine by inhibition of mycelial growth. The EC50 values for propamidine ranged from 0.406 to 3.647 μg/mL with a mean EC50 value of 1.616 ± 0.217 μg/mL. The frequency distribution of the EC50 values was a unimodal curve over a narrow range (Fig. 1) and the range of variation factor was 8.983. These unimodality and narrow range indicated that no resistant

4. Discussion

The ascomycete fungus S. sclerotiorum is highly destructive with a broad host range. In practice, application of fungicides is still the main method for control of Sclerotinia stem rot caused by S. sclerotiorum. However, the fungus has developed resistant to dicarboximide and benzimidazole fungicides worldwide due to their repeated application. Therefore, new chemical classes of fungicides with different mode of action are necessary for resistant management. Propamidine is an aromatic diamidine

Acknowledgements

This study was sponsored by the funding from National Key Technology Research and Development Program of China (2014BAD23B01) and China Postdoctoral Science Foundation (2016M592846).

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