Quantification and monitoring of Bacillus amyloliquefaciens GB03 colonization in Arugula in defense against Plutella xylostella and Spodoptera frugiperda

Author(s)

Rafaela Cristina dos Santos

• Document type: Doctoral Thesis
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2021-08-02

Examining board members

Jose Mauricio Simoes Bento; Mohamed Fokar

• Advisor: Jose Mauricio Simoes Bento

Abstract

Bacillus amyloliquefaciens GB03 is a plant growth-promoting rhizobacterium (PGPR) that occurs naturally in soil and is also available commercially, which has been showing positive results in plant growth promoting of different crops, induced systemic resistance to pathogens, greater tolerance drought and salinity and, more recently, studies have been effective in plant defense against insects attack in Arabidopsis. However, one of the main gaps today for the use of PGPR is its monitoring in the field. Therefore, the aims of this study were: to seek an efficient method for monitoring B. amyloliquefaciens GB03 in soil, to verify the effect of insect aboveground damage on PGPR colonization in the rhizosphere, to analyze whether the association with GB03 can affect the interaction or development of aboveground herbivorous insects and elucidate which mechanisms are involved in these interactions, in addition, we sought to investigate whether the degree of insect specialty can influence their response to interaction with the inoculated plant. All parameters analysed related to plant growth promotion were higher in inoculated plants with rhizobacterium than uninoculated plants. To monitoring, the primer corresponding to gyrA gene region was the most specific for GB03 strain. From the second week onwards, we observed that the rhizobacterium population began to decrease in the soil and the insect damage accelerated this process. In addition, it was found that the arugula inoculation with GB03 strain affects the feeding and performance of both P. xylostella, specialist caterpillars, and generalist caterpillars, Spodoptera frugiperda, as well as the P. xylostella oviposition preference and also that both inoculations with the GB03 strain and damage by caterpillars with different degrees of specialty the induced plant response measured in terms of emission of herbivory-induced plant volatiles (HIPVs). Other mechanisms that can be improved and involved in plant defense are induced systemic resistance (ISR) and glucosinolate production. It was found that when submitted to P. xylostella damage, arugula plants inoculated with GB03 strain presented a higher concentration of jasmonic acid compared to uninoculated plants. At the same time, it was verified that GB03 strain induced the gene expression of glucosinolates in arugula plants. (AU)

• FAPESP's process: 16/17952-2 - Quantification and tracking of niche colonization of the Bacillus amyloliquefaciens GB03 in Arugula (Eruca sativa) in defense against Plutella xylostella and Spodoptera frugiperda
• Grantee: Rafaela Cristina dos Santos
• Support Opportunities: Scholarships in Brazil - Doctorate