Fighting Plant Diseases Through the Application of Bacillus and Pseudomonas 2 Strains

SONIA FISCHER; ANALÍA PRÍNCIPE; FLORENCIA ALVAREZ; PAULA CORDERO; MARINA CASTRO; AGUSTINA GODINO; EDGARDO JOFRÉ; GLADYS MORI

Symbiotic Endophytes

Springer

Lugar: Heidelberg; Año: 2013; p. 165 - 193

Plant growth-promoting bacteria (PGPBs) are capable of colonizing plants and influencing 14 their growth by direct or indirect mechanisms. The direct mode of action occurs when 15 metabolites or compounds synthesized by microorganisms are provided to the plant- for 16 example phytohormones- or when the bacteria facilitate the plant?s uptake of certain 17 nutrients from the environment. In the indirect form of promotion, bacteria protect the plant 18 against phytopathogenic organisms through the induction of systemic resistance and/or by 19 the synthesis of antimicrobial compounds. The use of beneficial microorganisms as 20 biopesticides offers a promising alternative to the use of chemical pesticides and an 21 environmentally friendly strategy for agriculture. The PGPBs most studied and exploited as 22 biocontrol agents are the species of Bacillus and fluorescent Pseudomonas. These strains 23 produce a wide variety of metabolites involved in the biologic control of phytopathogenic 24 fungi -for example, extracellular enzymes, siderophores, antibiotics, hydrogen cyanide and 25 volatile organic compounds, among others. Antibiosis is one mechanism of biologic control 26 that is well-characterized in Bacillus and Pseudomonas strains both genetically and 27 biochemically. Among antibiotics identified in these two genera are include the cyclic 28 lipopeptides such surfactin, iturin and fengycin in the bacilli and phenazines, 2,4-diacetyl 29 phloroglucinol, pyoluteorin and pyrrolnitrin in the pseudomonads. 30 This chapter focusses on the ability of these PGPR to improve plant health in addition to 31 the mechanisms involved in their biocontrol capabilities.