Genetic resistance of some potato (Solanum tuberosum L.) cultivars to late blight caused by Phytophthora infestans (Mont) de Bary under natural conditions

Late blight caused by the Oomycete Phytophthora infestans is the most destructive and dreaded disease for potato growers.Crop resistance development by selecting varieties with resistance traits is a promising approach for disease control.This study, aimed to determine the response of potato varieties to Phytophthora infestans infection under natural conditions.Twelve potato varieties were screened using a completely randomized Fisher block design with three replicates.Growth parameters, disease incidence, disease severity, and yield were assessed.The contents of selected biochemical resistance markers in potato leaves and tubers were also determined.The results showed that the Manate blanc variety recorded the best collar diameter (2.96 0.49 cm).Dosa, Manate violet and Cipira varieties had the lowest incidence (7.60, 9.67 and 13.42% respectively), while Wouzang variety had the highest incidence (90%).The severity was low for the Cipira, Mondiale, Dosa and Manate violet varieties (2; 7, 9 and 11% respectively).The best yield was obtained from the Dosa variety (42.092.52 t. ha -1 ).In terms of biochemical parameters, Bamso variety produced the lowest phenolic compound content (2.130.32g/g PF) compared than Manate violet variety (5.29 1.52 g/g PF).Phenylalanine ammonialyase (PAL) enzyme activity was highest in leaves of the Manate blanc variety (182.7259.87A 290/min/mg) and in tubers of the Mondiale variety (439.5181.59A 290/min/mg).Polyphenol oxidase (PPO) activity was high in leaves and tubers of the Panamera variety (5.450.69 and 3.440.70A 330/min/mg respectively).The Cipira and Dosa varieties, with their low incidence and severity of late blight and good yields, may be the best suited for an integrated disease management strategy.