Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/10/2006
Publication Date: 4/1/2007
Citation: Frost, K.E., Rouse, D., Jansky, S.H. 2007. Considerations for Verticillium wilt resistance evaluation in potato. Plant Disease. 91(4):360-367. Interpretive Summary: Verticillium wilt is a serious potato disease caused by the soil-borne fungi Verticillium dahliae and V. albo-atrum. The most cost effective long term control strategy is the development of varieties with resistance to the disease. Resistance screening is often based on symptom expression or the quantification of pathogen populations in stems and roots of infected plants. In this study, we compared resistance screening assays to determine which most effectively identifies resistant plants. In one year, pathogen population assays were able to predict yield loss due to disease, while in another year, symptom expression more effectively predicted yield loss. Pathogen population assays based on stem sap provided more repeatable results than those based on dried stems. These data highlight the importance of characterizing the effect of environment on the relationship among pathogen population sizes in plant tissues, disease symptoms and yield loss.
Technical Abstract: Verticillium wilt (Vw), caused by the soil-borne fungi Verticillium dahliae and V. albo-atrum, is an important disease of potato (Solanum tuberosum L.). Host plant resistance is a promising method of Vw control. Culture-based methods that quantify the pathogen in host tissue are often used for Vw resistance screening. To evaluate the processing time, accuracy, and precision of these methods, 46 clones were planted in a field naturally infested with V. dahliae to collect data on visual disease symptoms, pathogen populations, and yield. In 2002, disease severity explained 43.4% of the variability of yield loss, but the linear relationship between stem colonization and yield loss was not significant. In 2003, stem colonization explained 57.5% of the variability of yield loss, while disease severity explained less than 2% of the variability of yield loss. Correlations comparing clone ranks from repeated pathogen measurements indicated that culturing sap from individual stems or bulked stems generated more repeatable clone rankings than culturing dried stems. Clone rankings were more repeatable between years if pathogen measurements were made earlier in the growing season. It is important to characterize the effect of the environment on the relationship among pathogen population sizes in plants, disease symptoms and yield loss.