Microbial basis of Fusarium wilt suppression by Allium cultivation

Tomoki Nishioka,Hideyuki Tamaki,Issei Kobayashi,Yuhko Kobayashi,Kyosuke Yamamoto,Haruhisa Suga,Malek Marian,Masafumi Shimizu

doi:10.1038/s41598-018-37559-7

Abstract

Crop rotation and intercropping with Allium plants suppresses Fusarium wilt in various crops. However, the mechanisms underlying this phenomenon have not been fully elucidated. This study was designed to assess the role of microorganisms inhabiting Allium rhizospheres and antifungal compounds produced by Allium roots in Fusarium wilt suppression by Allium cultivation. Suppression of cucumber Fusarium wilt and the pathogen multiplication by Allium (Welsh onion and/or onion)-cultivated soils were eliminated by heat treatment at 60 °C, whereas those by Welsh onion-root extract were lost at 40 °C. The addition of antibacterial antibiotics eliminated the suppressive effect of Welsh onion-cultivated soil on pathogen multiplication, suggesting the contribution of antagonistic gram-negative bacteria to the soil suppressiveness. The Illumina MiSeq sequencing of 16S rRNA gene amplicons revealed that genus Flavobacterium was the predominant group that preferentially accumulated in Allium rhizospheres. Flavobacterium species recovered from the rhizosphere soils of these Allium plants suppressed Fusarium wilt on cucumber seedlings. Furthermore, confocal laser scanning microscopy revealed that Flavobacterium isolates inhibited the multiplication of the pathogen in soil. Taken together, we infer that the accumulation of antagonistic Flavobacterium species plays a key role in Fusarium wilt suppression by Allium cultivation.

Highlights

Fusarium oxysporum has an extremely broad range of hosts and is one of the most devastating soil-borne pathogens, causing symptoms such as damping-off, root rot, and vascular wilt in crop plants[1,2]
We first investigated whether microorganisms inhabiting Allium rhizospheres and antifungal compounds produced by Allium roots contribute to the suppression of cucumber Fusarium wilt caused by F. oxysporum f. sp. cucumerinum (Focu) isolate GUS77, which was used as a representative pathogenic isolate of F. oxysporum
The severity of cucumber Fusarium wilt was significantly reduced in Allium (Welsh onion and onion)-cultivated soils compared with non-cultivated soil and cucumber-cultivated soil (P < 0.01) (Fig. 1a), indicating that Allium cultivation conferred cucumber Fusarium wilt suppressiveness to soil

Summary

Introduction

Fusarium oxysporum has an extremely broad range of hosts and is one of the most devastating soil-borne pathogens, causing symptoms such as damping-off, root rot, and vascular wilt in crop plants[1,2]. It can saprophytically survive on soil and plant debris in the absence of a host[3] and remain viable for a long time by producing chlamydospores, thereby making Fusarium wilt very difficult to control. We first investigated whether microorganisms inhabiting Allium rhizospheres and antifungal compounds produced by Allium roots contribute to the suppression of cucumber Fusarium wilt caused by F. oxysporum f. The identified bacteria were isolated and assessed for their ability to suppress cucumber Fusarium wilt by culture-dependent measures to elucidate the importance of the predominant rhizobacteria of Allium plants in Fusarium wilt suppression

Methods

Results

Conclusion