Zinc and Copper Enhance Cucumber Tolerance to Fusaric Acid by Mediating Its Distribution and Toxicity and Modifying the Antioxidant System.

Ruirui Wang,Aichen Liang,Jian Huang,Ying Wang,Min Wang,Luis Alejandro Jose Mur,Shiwei Guo

doi:10.3390/ijms21093370

Abstract

Fusaric acid (FA), the fungal toxin produced by Fusarium oxysporum, plays a predominant role in the virulence and symptom development of Fusarium wilt disease. As mineral nutrients can be protective agents against Fusarium wilt, hydroponic experiments employing zinc (Zn) and copper (Cu) followed by FA treatment were conducted in a glasshouse. FA exhibited strong phytotoxicity on cucumber plants, which was reversed by the addition of Zn or Cu. Thus, Zn or Cu dramatically reduced the wilt index, alleviated the leaf or root cell membrane injury and mitigated against the FA inhibition of plant growth and photosynthesis. Cucumber plants grown with Zn exhibited decreased FA transportation to shoots and a 17% increase in toxicity mitigation and showed minimal hydrogen peroxide, lipid peroxidation level with the increased of antioxidant enzymes activity in both roots and leaves. Cucumber grown with additional Cu absorbed less FA but showed more toxicity mitigation at 20% compared to with additional Zn and exhibited decreased hydrogen peroxide level and increased antioxidant enzymes activity. Thus, adding Zn or Cu can decrease the toxicity of the FA by affecting the absorption or transportation of the FA in plants and mitigate toxicity possibly through chelation. Zn and Cu modify the antioxidant system to scavenge hydrogen peroxide for suppressing FA induction of oxidative damage. Our experiments could provide a theoretical basis for the direct application of micro-fertilizer as protective agents in farming.

Highlights

The soil-borne fungus Fusarium oxysporum has been identified as the fifth most important fungus in plant pathology as it causes vascular wilt disease in more than 100 different crops [1]
To test the link between Fusaric acid (FA) phytotoxicity and metal ions, three-week-old cucumber plants were hydroponically fed with solutions containing either Fe, Mn, Cu or Zn for 24 h before adding 2 μg mL−1 FA
FA treated plants exhibited progressive wilt of the stem and new leaf, with necrotic roots which came to be seen in the leaves and resulting in the wilting of the entire plant (CK + FA)

Summary

Introduction

The soil-borne fungus Fusarium oxysporum has been identified as the fifth most important fungus in plant pathology as it causes vascular wilt disease in more than 100 different crops [1]. FA causes the reduction of root elongation in Arabidopsis and date palm [13,14] and root cell dysfunction in tomato and cucumber seedlings [15,16]. These all confirm the major and even decisive role of FA in the disease progression. Fusarium wilt is controlled through pesticides, chemical soil fumigation and use of resistant cultivars. Considering the environmental effects of synthetic pesticides, their high costs and challenging application procedure using nutritional regulation as protective strategies represents worthwhile and promising alternative

Methods

Results

Conclusion