Nitrate Increased Cucumber Tolerance to Fusarium Wilt by Regulating Fungal Toxin Production and Distribution.

Jinyan Zhou,Ruirui Wang,Shiwei Guo,Zechen Gu,Asanjan Saydin,Yuming Sun,Qirong Shen,Min Wang

doi:10.3390/toxins9030100

Jinyan Zhou, Ruirui Wang + Show 6 more

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https://doi.org/10.3390/toxins9030100

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Abstract

Cucumber Fusarium wilt, induced by Fusarium oxysporum f. sp. cucumerinum (FOC), causes severe losses in cucumber yield and quality. Nitrogen (N), as the most important mineral nutrient for plants, plays a critical role in plant–pathogen interactions. Hydroponic assays were conducted to investigate the effects of different N forms (NH4+ vs. NO3‒) and supply levels (low, 1 mM; high, 5 mM) on cucumber Fusarium wilt. The NO3‒-fed cucumber plants were more tolerant to Fusarium wilt compared with NH4+-fed plants, and accompanied by lower leaf temperature after FOC infection. The disease index decreased as the NO3‒ supply increased but increased with the NH4+ level supplied. Although the FOC grew better under high NO3− in vitro, FOC colonization and fusaric acid (FA) production decreased in cucumber plants under high NO3− supply, associated with lower leaf membrane injury. There was a positive correlation between the FA content and the FOC number or relative membrane injury. After the exogenous application of FA, less FA accumulated in the leaves under NO3− feeding, accompanied with a lower leaf membrane injury. In conclusion, higher NO3− supply protected cucumber plants against Fusarium wilt by suppressing FOC colonization and FA production in plants, and increasing the plant tolerance to FA.

Highlights

Cucumber Fusarium wilt, a common fungal disease caused by the soil-borne pathogenFusarium oxysporum f. sp. cucumerinum (FOC), leads to severe losses in the production of cucumbers worldwide [1,2]
It was reported that fusaric acid (FA) is the critical causal agent of Fusarium wilt through leaf cell membrane injury [6,7]
Cucumber plants infected by Fusarium oxysporum f. sp. cucumerinum (FOC) differed notably in their disease symptoms at 12 days post inoculation when the plants were at the flowering stage (Figure 1a)

Summary

Introduction

Cucumber Fusarium wilt, a common fungal disease caused by the soil-borne pathogenFusarium oxysporum f. sp. cucumerinum (FOC), leads to severe losses in the production of cucumbers worldwide [1,2]. Cucumber Fusarium wilt, a common fungal disease caused by the soil-borne pathogen. Cucumerinum (FOC), leads to severe losses in the production of cucumbers worldwide [1,2]. This pathogen can survive for long periods in the soil and invade cucumbers at any stage of development. The visible symptoms of Fusarium wilt disease are necrotic lesions, followed by foliar yellowing, wilting, vascular tissue damage, and plant death [1], attributed to mycelium colonization and toxins production of the pathogen [4]. Toxins 2017, 9, 100 development of plant disease symptoms induced by the infection of some Fusarium species [5]. It was reported that FA is the critical causal agent of Fusarium wilt through leaf cell membrane injury [6,7]

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