|ROJAS, A - Michigan State University|
|KIRK, W - Michigan State University|
|GACHANGO, E - Michigan State University|
|DOUCHES, D - Michigan State University|
Submitted to: Journal of Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2013
Publication Date: 1/1/2014
Citation: Rojas, A., Kirk, W.W., Gachango, E., Douches, D.S., Hanson, L.E. 2014. Tuber blight development in potato cultivars in response to different genotypes of Phytophthora infestans. Journal of Phytopathology. 162(1):33-42.
Interpretive Summary: Potato late blight is one of the most devastating diseases of potato under cool, wet conditions. Potato tubers are an important factor in spread and survival of the pathogen, Phytophthora infestans. Several different genotypes of P. infestans have been associated with the disease. Introductions of new genotypes can affect how the disease is managed. During 2009-2010, a late blight epidemic spread through several states of the U.S. that was characterized by a new P. infestans genotype, designated US-22. The aim of this research was to examine the interaction between potato tubers with the US-22 genotype in comparison with previously identified genotypes of the pathogen. Tuber blight development was characterized based on symptoms of darkened tissue. The response of the potato tubers indicated that P. infestans genotype US-8 was more aggressive than US-22, but US-22 isolates from potato were more virulent on tubers than those from tomato. A cultivar, Jacqueline Lee, showed consistent tuber blight resistance to all genotypes tested, but other potato cultivars varied in susceptibility. Although US-22 was less virulent than US-8, it can still infect tubers and should be considered in screening for host resistance.
Technical Abstract: Potato late blight, caused by Phytophthora infestans, is one of the most devastating diseases in potatoes, causing significant loses under disease-conducive conditions. Migrations or introduction of new genotypes to a specific region impose a different set of criteria for consideration for potato growers and researchers. During 2009-2010, the North Eastern US suffered a late blight epidemic that quickly spread through several states. The epidemic was characterized by the appearance of a genotype designated as US-22, which was isolated from tomato and potato plants. Since potato tubers are an essential component of epidemics, different cultivars were challenged with various genotypes of P. infestans, including different isolates of the genotype US-22 to examine the response. Tuber blight development was characterized in terms of tissue darkening and lenticel infection expressed as relative area under the disease progress curve (RAUDPC). The response indicated that US-8 was more aggressive than US-22, but US-22 isolates obtained from potato were more virulent on potato than those from tomato. The periderm responses to infection tended to be low, but still US-8 was more likely to infect than US-22. The cultivar Jacqueline Lee showed consistent tuber blight resistance. Although US-22 was less virulent in comparison to US-8, it can still infect tubers and should be considered as a significant factor in managing late blight through host resistance.