Relation of leaf epidermal characteristics with susceptibility and resistance of potato (Solanum tuberosum) to late blight disease (Phytophthora infestans)

An experiment was conducted during 2000-2001 to study leaf epidermal characteristics of 4 varieties of potato (Solanum tuberosum L.) (2 resistant : 'Kufri Jyoti' and 'Kufri Badshah' and 2 susceptible : 'Kufri Ashoka' and 'Kufri Chandramukhi') differing in their resistance or susceptibility to late blight disease [Phytophthora infestans (Mont) de Bary]. The cuticle was significantly thicker in the resistant varieties on both the adaxial (5.8 and 6.9 mum) and the abaxial (5.2 and 5.4 mum) surfaces of the leaf than that of the susceptible varieties. The cuticle-cum-epidermis thickness also showed a similar trend. The size (23.2 and 23.8 mum, abaxial surface), frequency (83.2 and 62.8/mm(2), adaxial surface) and index of stomata (17.0 and 18.5 on adaxial and 38.0 and 38.9 on abaxial surfaces) were significantly higher in the susceptible varieties. The resistant varieties had significantly higher values for size of trichomes on both the leaf surfaces (588.0 and 735.6 mm on the adaxial and 667.8 and 600.0 mm on the abaxial surface). Resistant varieties also had significantly higher frequency of trichomes (640.7 and 676.9/cm(2), adaxial surface).