Effects of manganese and zinc on the growth process of Phytophthora nicotianae and the possible inhibitory mechanisms

Yifang Luo; Aimei Yao; Mouyi Tan; Zhenlun Li; Ling Qing; Shuiying Yang

doi:10.7717/peerj.8613

Effects of manganese and zinc on the growth process of Phytophthora nicotianae and the possible inhibitory mechanisms

PeerJ. 2020 Feb 20:8:e8613. doi: 10.7717/peerj.8613. eCollection 2020.

Authors

Yifang Luo¹, Aimei Yao¹, Mouyi Tan¹, Zhenlun Li², Ling Qing¹, Shuiying Yang¹

Affiliations

¹ Chongqing Key Laboratory of Plant Disease Biology, College of Plant Protection, Southwest University, Chongqing, China.
² Chongqing Key Laboratory of Soil Multi-Scale Interfacial Process, College of Resources and Environment, Southwest University, Chongqing, China.

Abstract

Background: Phytophthora nicotianae is a fungal soil-borne pathogen that damages various plant species. Mancozeb and Zineb, fungicides containing manganese (Mn) and zinc (Zn) as the main components, are widely used to control the diseases caused by Phytophthora. However, the inhibition mechanism is still unclear. The purpose of this study was to examine the effects of Mn and Zn on P. nicotianae and to determine possible inhibitory mechanisms of Mn and Zn on sporangiogenesis of P. nicotianae.

Methods: The mycelial growth, sporangium generation, zoosporogenesis and zoospore germination of P. nicotianae were observed under Mn and Zn treatments. The gene (csn4 and csn7) expression levels of P. nicotianae in different growth stages were examined. Csn4 and csn7 gene expression, superoxide dismutase (SOD) activity, catalase (CAT) activity and malondialdehyde (MDA) content were tested at the stage of sporangiogenesis under different Mn and Zn concentrations.

Results: Mycelial growth of P. nicotianae was significantly inhibited by Mn from ≥1 mg/L concentration and by Zn from ≥10 mg/L. The sporangia production, sporangia release, and zoospore germination of P. nicotianae were significantly reduced by Mn at all concentrations, while treatment with Zn from ≥0.5 mg/L concentration significantly inhibited the same processes. At the same concentration, the inhibition rate of Mn on the growth process of P. nicotianae was higher than that of Zn. The csn4 and csn7 gene transcription of P. nicotianae were significantly reduced by all treatments with Mn and Zn at the stage of sporangiogenesis. With the increase of Mn concentration, the activities of SOD and CAT increased to maxima and then decreased, and the content of MDA gradually increased during sporangiogenesis of P. nicotianae. The sporangia production of P. nicotianae was significantly positively correlated with the expression levels of the genes csn4 and csn7.

Conclusion: The inhibitory effect of Mn on the growth process of P. nicotianae was stronger than that of Zn, especially on sporangiogenesis and zoosporogenesis. A possible mechanism of the inhibitory effect on sporangiogenesis of P. nicotianae was that Mn and Zn acted by inhibiting the expression levels of the genes csn4 and csn7 and by affecting antioxidant enzyme activity (further resulting in lipid peroxidation) in the sporangium of P. nicotianae.

Keywords: Antioxidant system; Gene expression; Inhibitory mechanisms; Manganese; Phytophthora nicotianae; Zinc.

Grants and funding

This work was supported financially by the National Key Research and Developmental Program of China (2016YFC0502303). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.