Regulation of defense-related enzymes associated with bacterial spot resistance in Tomato |
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Authors: | R Kavitha S Umesha |
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Institution: | (1) Dept. of Applied Botany, Seed Pathology and Biotechnology, University of Mysore, 570 006 Manasagangotri, Mysore, Karnataka, India;(2) Present address: Dept. of Plant Pathology, Physiology & Weed Science, Virginia Polytechnic Institute & State University, Virginia Beach, VA, USA |
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Abstract: | Twenty tomato (Solanum lycopersicon) cultivars were screened for resistance against bacterial spot disease incited byXanthomonas axonopodis pv.vesicatoria under field conditions with and without pathogen infection. Screening was done by artificially inoculating aX. axonopodis pv.vesicatoria suspension to 4-week-old tomato seedlings and observing them for typical symptoms of the disease. Seedlings were categorized
into highly resistant, resistant, susceptible and highly susceptible cultivars on the basis of disease incidence. Tomato cultivars
were screened for defense-related enzymes, total phenols and lignin contents. The temporal patterns of all these enzymes were
estimated with a moderately susceptible tomato cultivar. Native PAGE analysis of both peroxidase (POX) and polyphenol oxidase
(PPO) was carried out for the time course of enzyme activities and also by selecting three different tomato cultivars, following
infection with the pathogen. Based on the inducible amounts of these enzymes upon pathogen infection, the tomato cultivars
were correlated with the disease incidence under field conditions. A significant (P≤0.05) correlation was observed between the degree of host resistance and the enzyme levels. In highly resistant tomato cultivars
the enzyme levels, total phenols and lignin contents were increased in comparison with highly susceptible tomato cultivars.
Isoform analysis of POX and PPO enzymes indicated a clear difference between resistant and susceptible tomato cultivars in
the number of isoforms and also in the intensity of each isoform in the presence of pathogen infection. The possible regulation
of defense-related enzymes in imparting host resistance is discussed.
http://www.phytoparasitica.org posting March 11, 2008. |
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Keywords: | Peroxidase phenylalanine ammonia lyase polyphenol oxidase Solanum lycopersicon susceptibility Xanthomonas axonopodis pv vesicatoria |
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