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Biochemical Evaluation of Resistance Responses of Potato to Different Isolates of Alternaria solani

May 2010 , Volume 100 , Number  5
Pages  454 - 459

Hadis Shahbazi, Heshmatollah Aminian, Navazollah Sahebani, and Dennis A. Halterman

First, second, and third authors: Department of Plant Protection, Aboryhan Campus, Tehran University, P.O. Box 33955-159, Tehran, Iran; and fourth author: U.S. Department of Agriculture-Agricultural Research Service, Vegetable Crops Research Unit, Madison, WI 53706.

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Accepted for publication 18 January 2010.

The resistance phenotypes of nine potato cultivars to five isolates of Alternaria solani, causal agent of early blight, were studied after inoculation and growth under greenhouse conditions. We identified potato cultivars with both susceptible and resistant phenotypes as well as A. solani isolates with varying degrees of aggressiveness. Two potato cultivars and two pathogen isolates were selected for biochemical analysis of phenol production and peroxidase activity after inoculation. Phenol compounds were evaluated 2, 4, 6, and 8 days after inoculation, while peroxidase activities were monitored daily for 10 days. Native polyacrylamide electrophoresis was used to identify one protein with peroxidase activity in extracts taken 6 days after inoculation. Significantly higher peroxidase activity as well as total phenol content in potato was correlated with resistance in the Iranian potato cultivar Diamond. Variability of responses within the same cultivar to different isolates of A. solani suggests genotypic diversity between isolates that results in phenotypic diversity for pathogen aggressiveness.

Additional keywords:disease resistance, host defense responses, plant peroxidase, plant phenolics.

The American Phytopathological Society, 2010