Evaluation of Pseudomonas sp. PCI2 for the control of Alternaria alternata leaf spot of tomato plants

PASTOR, NICOLÁS; ROSAS, SUSANA; ROVERA, MARISA

Medellín

Workshop; 9th International and 1st Latin American PGPR Workshop; 2012

Universidades Colombianas: UN, EAFIT, Antioquía

Tomato plants are susceptible, among other fungi, to A. alternata, which causes stem canker and leaf spot. Plant fungal diseases are managed by the application of chemical fungicides. Biological control is being considered as an alternative or a supplemental way of reducing the use of chemicals in agriculture. Previously, Pseudomonas sp. PCI2 showed promise to control tomato damping-off caused by Sclerotium rolfsii. The present study focuses to advance in the characterization of the antagonistic activity of PCI2 and to evaluate its potential to control tomato leaf spot caused by A. alternata. PCR assays were carried out to detect phlD, phz, prnD and pltC. Pseudomonas sp. PCI2 did not show amplification with primers specific for antibiotic biosynthetic genes encoding DAPG, PCA, PRN and PLT. In addition, we studied the production of siderophores; the development of a green coloured pigment in SM by Pseudomonas sp. PCI2 after 24 h of incubation indicated production of siderophores. This strain produced 45% units of siderophores in SM medium. Pseudomonas sp. PCI2 was evaluated for control of tomato leaf spot caused by A. alternata under controlled growth chamber conditions. PCI2 reduced the percentage of infected tomato leaves by 36% and increased shoot dry weight of seedlings by 65%. Pseudomonas sp. PCI2 may be a good biological control agent of tomato phytopathogenic fungi. However, more researches are needed for this statement. Further field studies must be conducted to analyze the real potential of strain PCI2 in field conditions. Finally, studies are also needed to determine the modes of action of this bacterium, its population density after application and the best form of introduction into the host.