Influence of bacterial consortia in maize (Zea mays) growth promotion

Author(s)

Heloísa Defant

• Document type: Master's Dissertation
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2023-11-21

Examining board members

Maria Carolina Quecine Verdi; Fernando Dini Andreote; Manuella Nóbrega Dourado Ribeiro

• Advisor: Maria Carolina Quecine Verdi

Abstract

The microbiote associated with plants acts through several mechanisms aimed at conferring advantages in the fitness of the host plant. One of these mechanisms is the promotion of plant growth, which has been exploited for commercial use and practical application in agriculture. Plant growth promoting bacteria (BPCPs) act directly or indirectly, through the supply of nutrients, production of phytohormones, competition with pathogens and others. In general, the bacterial consortia present better performance in relation to the promotion of plant growth when compared to the use of strains individually increasing the resistance to adverse effects and functional complementarity in the ecosystem Thus, the present work aimed to evaluate the effect of several types of bacterial consortia on maize crop. Initially, bacterial strains with the potential to promote maize growth were isolated, characterized and selected and consortia were formed with complementarity of functions between bacteria and according to diversity or similarity of taxa. It was observed that more diverse consortia present better performance in promoting maize growth compared to consortia that use only one bacterial genus, especially in the shoot. The strains Arthrobacter globiformis CNM05 and Siphonobacter intestinalis CNM19 were statistically better in all variables for A. globiformis CNM05 and shoot length, shoot dry weight and root dry weight for S. intestinalis CNM19 when compared to the consortia in which they were inserted. Afterwards, consortia formed by strains obtained from the corn crop and a consortium formed by strains obtained from various sources, which had previously presented promising results in the maize crop, were evaluated. The consortium of diverse origin presented better performance if compared to the consortia obtained from maize in shoot dry weight, as well as was better than the strains applied individually in shoot dry weight and root dry weight. Finally, in relation to the diverse consortium, composed of Azospirillum brasilense Ab-V5, Bacillus thuringiensis RZ2MS9, Delftia acidovorans RZ4MS18 and Pantoea agglomerans 33.1, the study of genes related to growth promotion of bacterial strains was carried out. Regarding the genes related to plant growth promotion present in the strains, 16% are present in all strains, 43% of the genes can be found in combinations and 41% of the genes are unique to the strains. Comparing in vitro results with the evaluation of the presence of genes, it is observed that among the strains A. brasilense Ab-V5, B. thuringiensis RZ2MS9, D. acidovorans RZ4MS18 and P. agglomerans 33.1, only D. acidovorans RZ4MS18 and P. agglomerans 33.1 present a complete tryptophan-dependent pathway for the production of complete IAA, although all of them presented positive results in the in vitro test. For phosphate solubilization, although all strains present genes related to phosphate solubilization, only P. agglomerans 33.1 has phy genes, encoding phytase enzymes, and is also the only one that presented positive results in in vitro test. Through this work, it can be affirmed that consortia formed by strains obtained from sources present better performance than consortia obtained by strains of the same origin. The presence of genes related to a trait in strains that do not present in vitro results when applied individually can potentiate the result of positive strains in vitro, oppening a new perspective in researchs about microorganism-plant interaction. (AU)

• FAPESP's process: 21/11983-1 - Construction of bacterial consortium to promote maize growth: study of interaction, growth promotion and modulation of gene expression
• Grantee: Heloísa Defant
• Support Opportunities: Scholarships in Brazil - Master