Volatile Compounds of Endophytic Bacillus spp. have Biocontrol Activity Against Sclerotinia sclerotiorum

Abstract

To develop an effective biological agent to control Sclerotinia sclerotiorum, three endophytic Bacillus spp. strains with high antagonistic activity were isolated from maize seed and characterized. In vitro assays revealed that the Bacillus endophytes could produce volatile organic compounds (VOC) that reduced sclerotial production and inhibited mycelial growth of S. sclerotiorum. Gas chromatography-mass spectrometry revealed that the selected strains produced 16 detectable VOC. Eight of the produced VOC exhibited negative effects on S. sclerotiorum, while a further four induced accumulation of reactive oxygen species in mycelial cells. A mixture of VOC produced by Bacillus velezensis VM11 caused morphological changes in the ultrastructure and organelle membranes of S. sclerotiorum mycelial cells. The bromophenol blue assay revealed a yellow color of untreated fungal mycelium, which grew faster and deeper from 24 to 72 h postinoculation, as an indication of reduced pH. The potassium permanganate (KMnO) titration assay showed that the rate of oxalic acid accumulation was higher in minimal salt liquid medium cultures inoculated with untreated fungal plugs compared with the Bacillus VOC-treated ones. Interestingly, biological control assays using host-plant leaves challenged with treated fungal mycelial plugs produced reduced lesions compared with the control. These findings provide new viable possibilities of controlling diseases caused by S. sclerotiorum using VOC produced by Bacillus endophytes.

Aureobasidium pullulans volatilome identified by a novel, quantitative approach employing SPME-GC-MS, suppressed Botrytis cinerea and Alternaria alternata in vitro

“…The utilisation of biocontrol agents such as microbial VOCs represent a more environmentally friendly 4,5 alternative for plant disease management. Research on microbial VOCs fumigation has demonstrated successful antifungal effects on a large spectrum of pathogenic fungi and bacteria 3,33 . Despite these advances, plant diseases caused by B. cinerea and A. alternata remain a challenge 14,34 .…”

“…Knowing the negative effects of microbial VOCs on fungal physiological functions including mycelial growth, spore germination, sporulation and sclerotial development 11,33 , we studied the antifungal effects of A. pullulans VOCs on two fungi B. cinerea and A. alternata, responsible for disease losses in a wide range of agricultural crop plants. We observed a strong reduction of pathogen mycelial growth and conidia germination of the two www.nature.com/scientificreports www.nature.com/scientificreports/ pathogens by A. pullulans VOCs.…”

Bacillusspecies in soil as a natural resource for plant health and nutrition

“…Among these VOC, 2,4‐di‐tert‐butylthiophenol and benzothiazole had strong inhibitory effect against Monilinia fructicola and C. gloeosporioides (Gao et al ). Massawe et al () reported 16 different types of VOC from three different species of Bacillus and eight of these VOC could inhibit the growth of S. sclerotiorum . B. velezensis SQR‐9 produced 22 different VOC of which nine compounds showed antibacterial activity against R. solanacearum (Raza et al ).…”

Profiling for Bioactive Peptides and Volatiles of Plant Growth Promoting Strains of the Bacillus subtilis Complex of Industrial Relevance

“…Also, the members of the B. subtilis complex produce an extensive pattern of these volatile metabolites which are listed in Table 3 . Their nature and action gain increasing attention concerning plant growth promotion ( Ryu et al, 2003 ; Asari et al, 2016 ; Wu et al, 2018 ), biocontrol against phytopathogenic bacteria ( Rajer et al, 2017 ; Tahir et al, 2017a ; Xie et al, 2018 ) and fungi ( Fernando et al, 2005 ; Zhang et al, 2013 ; Chaves-Lopez et al, 2015 ; Asari et al, 2016 ; Massawe et al, 2018 ; Hassan et al, 2019 ), induction of systemic resistance against phytopathogens ( Ryu et al, 2004 ; Farag et al, 2006 , 2013 ) as well as steering of gene expression and metabolic processes in plants ( Tahir et al, 2017b ). Similar to bioactive peptides the members of the B. subtilis complex show characteristic specificities concerning the produced volatiles.…”