Bacillus thuringiensis RZ2MS9, a tropical plant growth‐promoting rhizobacterium, colonizes maize endophytically and alters the plant's production of volatile organic compounds during co‐inoculation with Azospirillum brasilense Ab‐V5

Abstract

The beneficial features of Bacillus thuringiensis (Bt) are not limited to its role as an insecticide; it is also able to promote plant growth interacting with plants and other plant growth-promoting rhizobacterium (PGPR). The PGPR Bt strain RZ2MS9 is a multi-trait maize growth promoter. We obtained a stable mutant of RZ2MS9 labelled with green fluorescent protein (RZ2MS9-GFP). We demonstrated that the Bt RZ2MS9-GFP successfully colonizes maize's roots and leaves endophytically. We evaluated whether RZ2MS9 has an additive effect on plant growth promotion when co-inoculated with Azospirillum brasilense Ab-V5. The two strains combined enhanced maize's roots and shoots dry weight around 50% and 80%, respectively, when compared to the noninoculated control. However, non-differences were observed comparing RZ2MS9 alone and when co-inoculated with Ab-V5, In addition, we used co-inoculation experiments in glass chambers to analyse the plant's volatile organic compounds (VOCs) production during the maize-RZ2MS9 and maize-RZ2MS9-Ab-V5 interaction. We found that the single and co-inoculation altered maize's VOCs emission profile, with an increase in the production of indoles in the co-inoculation. Collectively, these results increase our knowledge about the interaction between the Bt and maize, and provide a new possibility of combined application with the commercial inoculant A. brasilense Ab-V5.

Development of plant systemic resistance by beneficial rhizobacteria: Recognition, initiation, elicitation and regulation

“…Emerging evidence has indicated that plants can use volatiles as the language to communicate with diverse microbes (e.g., bacteria, fungi and virus), insects and other neighboring plants ( Ballhorn et al, 2013 ; Simpraga et al, 2016 ; Sharifi et al, 2018 ; de Almeida et al, 2021 ). Several kinds of volatiles (e.g., α-pinene and isothiocyanate) are often liberated by plants, which function as the cues for attracting insects ( Elzen et al, 1983 ).…”

Bacillus thuringiensis as a biofertilizer in crops and their implications in the control of phytopathogens and insect pests

“…Bt has been isolated from different plant tissues (root exudates, leaves samples, stems, etc) 14,23,24,28,30,38,43 and rhizosphere soil samples 25,26,56 . Specifically, Bt has been isolated from different agroeconomic crops (Fig.…”

“…1). 24,26,30,59,61–63 The reports published to date 22,23,30,61 showed a wide range of plant responses to the co‐inoculation of Bt plus PGPB. Vidal‐Quist et al 24 .…”

“…Bt strains may exhibit plant growth promotion traits that are common to other well‐known PGPB of the class Bacilli 9 . Plant growth promotion traits described for Bt include: synthesis of phytohormones such as IAA (indole acetic acid) 13–18,21–28,57 and ACC‐deaminase, 13,17–19,21,24,26,27 biological nitrogen (N 2 ) fixation, 13–15 ammonia (NH 3 ) production, 13,16 phosphate solubilization, 14–20,57 production of sideophores 17–19,21,57 and volatile organic compounds 29,30 …”

The Microbially Extended Phenotype of Plants, a Keystone against Abiotic Stress

“…However, the same synergistic natural microbial communities might negatively affect plants under more severe abiotic stresses or more extended periods of stress occurrence (91). Nevertheless, some plant multipartite interactions with plant growth promoting rhizobacterium (PGPR) in roots and endophytes in leaves play an unpredicted synergistic role by boosting plant development and triggering plant production of indoles (92); this highlights the importance of setting up more complex experimental approaches to address eco-evolutionary questions in these systems.…”