| dc.description.abstract | Potato tuber blight, caused by Phytophthora infestans, is an important component of the late blight pathosystem. Although the dynamics of tuber blight on potato (Solanum tuberosum) cultivars have been evaluated, the effects of climatic and soil variables on tuber blight incidence have not been adequately quantified. Field experiments were conducted at two distinct environments: in New York (1998–1999) using the A2 mating type (US-8 clonal lineage), and in Kenya (2000–2001) using the A1 mating type (US-1 clonal lineage). Fungicide applications were scheduled to vary the amount of blight infection. Foliar and tuber blight development, climatic variables, and soil variables were quantified during the cropping seasons. Fungicide application did not have a significant effect on the incidence of tuber blight at both locations. Soil temperature, precipitation, tuber depth, and cultivar resistance were significantly correlated with incidence of tuber blight at both locations. At Freeville, New York, precipitation when soil temperature was 16–18 °C had the highest correlation (r 2 = 0.632) with tuber blight, whereas soil moisture had the highest correlation (r 2 = 0.577) with tuber blight in Kenya. Path coefficient analysis showed that total precipitation during the epidemics and days when soil temperature was 16–18 °C had the largest direct effect on tuber blight in New York and at the field sites in Kenya. Regression models using atmospheric variables, soil variables, and cultivar resistance had moderate predictive ability of tuber blight at New York (0.44 < R 2 < 0.61) but low prediction in Kenya (0.40 < R 2 < 0.46). Similarly, cultivar specific models using foliar blight, atmospheric variables, and soil variables resulted in significant predictions of tuber blight in New York (R 2 > 0.46), whereas few regression equations for Kenya resulted in significant prediction of tuber blight. These results suggest that cultivar resistance, soil variables, and atmospheric variables are the main determinants of foliar and tuber blight infection when inoculum is present. Key words: Phytophthora infestans, Solanum tuberosum, tuber blight, cultivars, environmental factors, resistance | en |
