Utilisation of Carbon Sources by Pythium, Phytophthora and Fusarium Species as Determined by Biolog® Microplate Assay
Sammar Khalil*, Beatrix W Alsanius
Identifiers and Pagination:Year: 2009
First Page: 9
Last Page: 14
Publisher Id: TOMICROJ-3-9
Article History:Received Date: 28/11/2008
Revision Received Date: 5/12/2008
Acceptance Date: 28/12/2008
Electronic publication date: 15/1/2009
Collection year: 2009
open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.
This study examined the metabolic activity of pure cultures of five root pathogens commonly found in closed hydroponic cultivation systems (Phytophthora cryptogea (PC), Phytophthora capsici (PCP), Pythium aphanidermatum (PA), Fusariumoxysporum f.sp. radicis-lycopersici (FORL) and Fusarium solani (FS)) using sole carbon source utilisation in order to develop effective biocontrol strategies against these pathogens. Aliquots of 150 µL of the mycelial suspension were inoculated in each well of GN2 microtitre plates. On the basis of average well colour development and number of positive wells, the pathogens were divided into two groups, (i) PA and FORL and (ii) PC, PCP and FS. Group (i) was characterised by a short lag-phase, a rapid exponential phase involving almost all carbon sources offered and a long stationary phase, while group (ii) had a more extended lag-phase and a slower utilisation rate of the carbon sources offered. The three isolates in group (ii) differed significantly during their exponential phase. The lowest utilisation rate of carbon sources and number of sources utilised was found for PCP. Of the major group of carbon sources, six carbohydrates, three carboxylic acids and four amino acids were rapidly used by all isolates tested at an early stage. The carbon sources gentibiose, α-D-glucose, maltose, sucrose, D-trehalose, L-aspartic acid, L-glutamic acid, L-proline persisted to the end of the exponential phase.Moreover, similarities between the metabolic profiles of the tested pathogen and the those of the resident microflora could also be found. These findings are of great importance as regards the role of the resident microflora in the biocontrol.