Submitted to: Canadian Journal of Plant Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/11/2007
Publication Date: 3/15/2008
Citation: Nyankanga, R.O., Wein, H.C., Olanya, O.M. 2008. Relationship between incidence of late blight tuber rot, foliage blight control and the effect of weather and soil variables. Canadian Journal of Plant Pathology. 29:372-382. Interpretive Summary: The relationship of late blight disease, tuber blight and the effects of weather and soil variables were determined at 2 distinct environments of New York and Kenya during 1999 to 2001. In well replicated field experiments at the two sites where A2 (US8 clone) and A1 (US1 clone) respectively are dominant, foliar and tuber blight development, climatic and soil variables were quantified during three cropping seasons. Variation in tuber blight in New York and Kenya was detected. Stepwise multiple regression and correlation analysis identified combinations of variables associated with tuber blight such as cultivar characteristics, soil temperature and precipitation events. The research results can provide insight into the dynamics of tuber blight infection processes and be useful for tuber blight management strategies.
Technical Abstract: Potato tubers are often infected by Phytophthora infestans mainly by inocula produced on leaves or stems. Because of the linkage between foliage and tuber infection, the main control of tuber blight has been by fungicide control of foliage late blight. This study investigated the relationship between incidence of tuber blight and foliage disease development and how this relationship is affected by weather and soil variables in field experiments conducted in New York in 1998 - 1999 using the A2 mating type and in Kenya in 2000 - 2001 using the A1 mating type. Foliar fungicide spray regimes did not have a significant effect on overall tuber blight incidence. Incidence of tuber blight and foliar blight (AUDPC) was negatively correlated in NY but positively correlated in Kenya. Stepwise multiple regression and correlation analysis identified combinations of soil temperature, and amount and frequency of precipitation to be associated with variation in tuber blight incidence. Number of days with soil temperature 16-18°C had the largest direct effect while days of precipitation when foliage late blight was 5-50% had the largest total correlation with tuber blight. Development of multiple regression models using tuber resistance and depth, soil temperature, and precipitation had moderate predictive ability in NY (R2 =0.56) but poor prediction in Kenya (R2= 0.34). Generally, cultivar characteristics, soil temperature, and precipitation events moderated the relationship between foliage and tuber blight.