Location: Vegetable Crops ResearchTitle: Biochemical Evaluation of Resistance Responses of Potato to Different Isolates of Alternaria Solani Author
Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/23/2009
Publication Date: 5/1/2010
Citation: Shahbazi, H., Aminian, H., Sahebani, N., Halterman, D.A. 2010. Biochemical Evaluation of Resistance Responses of Potato to Different Isolates of Alternaria Solani. Phytopathology. 100(5):454-459. Interpretive Summary: We have identified potato cultivars that differ significantly in resistance to the early blight pathogen Alternaria solani. However, this resistance does not appear to be conferred by a single gene since we identified a wide spectrum of resistance types. This suggests that several genes involved in pathogen defense work together to increase resistance to A. solani in potato. We found that total phenol and peroxidase levels were significantly induced after inoculation with A. solani, regardless of the resistance type. We also found that total phenol levels were significantly higher in the resistant cultivar when compared to the susceptible cultivar suggesting that total phenol has an important role in resistance. In addition to differences between potato cultivars, we also found variability among isolates of A. solani collected from different regions. Some isolates were much more aggressive on potato than others. Our findings will impact potato breeders by providing methodologies that can be used to screen and select germplasm containing resistance to Alternaria solani.
Technical Abstract: 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 gel 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 changes in pathogen aggressiveness.